Synaptic plasticity in the hippocampus is a fundamental feature of brain function involved in the encoding of information, and the capability of synapses to express plasticity is itself activity-dependent. Numerous studies have identified molecules that are essential for induction and/or maintenance of synaptic plasticities. However, little is know about interaction between the hippocampus and other brain area. The amygdala transfers emotion to various brain regions including hippocampus and there are two kinds of projections to the hippocampus from the basolateral amygdala, direct and indirect pathway via the entorhinal cortex. The modulation is not uniform and ventral hippocampus receives more dense direct innervation, which is sensitive to stress. Activities of the direct and indirect pathways can modulate synaptic transmission in the hippocampus. Activation of locus caeruleus also influenced the transmission. These spatiotemporal and extra-hippocampal modulations of hippocampal synaptic plasticities provide new insights into the function of hippocampus. [J Physiol Sci. 2008;58 Suppl:S35]

抄録全体を表示

The dentate gyrus of the hippocampus has been implicated in behavioral effects of antidepressant drugs including selective serotonin reuptake inhibitors (SSRIs). The mossy fiber (MF) is the sole output of dentate granule cells and thus plays a pivotal role in regulation of hippocampal neuronal activity by the dentate gyrus. To test possible involvement of modification of the MF synapse in behavioral changes caused by SSRIs, we examined effects of chronic oral administration of fluoxetine, a widely used SSRI, on behaviors and the MF synaptic transmission in adult mice. Fluoxetine had multiple effects on behaviors and the MF synaptic transmission in a dose-dependent manner. At a lower dose, the fluoxetine treatment reduced activity of mice in a novel environment and affected modulation of the MF synaptic transmission by serotonin without noticeable effects on the synaptic transmission itself. At higher doses, however, it markedly increased fluctuation of home cage activity and anxiety-related behaviors, and also greatly reduced the large synaptic facilitation that is a characteristic of the mature MF synapse. This synaptic change was well correlated with the behavioral changes. In the dentate gyrus of mice treated with the higher dose of fluoxetine, expression of calbindin, a marker for the mature granule cells, was significantly reduced. These results indicate that fluoxetine at high doses can disrupt the maturation state of the dentate gyrus and the MF synaptic transmission in adult mice, which may underlie the destabilized behavior in the treated mice. [J Physiol Sci. 2008;58 Suppl:S35]

抄録全体を表示

Neuregulin-1 (NRG1) and epidermal growth factor (EGF) bind to the ErbB receptor family and are suggested to be a risk gene for schizophrenia, although etiological or pathological mechanisms remain to be characterized. We reported that neonatal exposure to the proinflammatory cytokine, EGF, perturbs GABAergic development, leading to the behavioral and cognitive impairments that are often implicated in schizophrenia animal models. In the present study, we examined influences of in vivo NRG1 administration on GABAergic development and neurobehavioral consequences, and compared their behavioral characteristics with those induced by EGF. We produced and purified mouse Ig-NRG1beta protein (MW 25000) using the bacterial recombinant system and subcutaneously administered it to neonatal mice (C57BL/6J). Repeatedly injected Ig-NRG1beta permeated the blood-brain barrier and activated ErbB4 receptors in neonatal brain, promoting synaptic maturation of GABAergic neurons in the neocortex. At the adult stage, the Ig-NRG1beta-treated mice showed normal response in the fear-conditioning task, but were impaired in its latent learning paradigm. Prepulse inhibition (PPI) of the Ig-NRG1beta-treated mice was decreased, which are similar to the behavioral features of EGF-treated mice. These results suggest that endogenous production or release of NRG1 following brain injury and stress results in distinct cognitive and behavioral abnormalities. The therapeutic potential of ErbB receptor inhibitors will be discussed in these models. [J Physiol Sci. 2008;58 Suppl:S35]

抄録全体を表示

Although many factors have been implicated in the regenerative response of peripheral axons to nerve injury, the signals that prompt neurons to extend processes in peripheral nerves after axotomy are not well understood. Oxidized recombinant human galectin-1 (rhGAL-1/Ox), which lacks lectin activity, promotes initial axonal growth in an in vitro peripheral nerve regeneration model at low concentrations (pg/ml). At a similarly low concentration, rhGAL-1/Ox has also been shown to be effective in enhancing axonal regeneration using in vivo experiments. Moreover, the application of functional anti-rhGAL-1 antibody strongly inhibited axonal regeneration in vivo as well as in vitro. Galectin-1 has been proved to be expressed in the regenerating sciatic nerves as well as in both sensory neurons and motor neurons, and to be secreted into extracellular space and subsequently oxidized. Externalized GAL-1/Ox has been found to stimulate macrophages to secrete an axonal regeneration-promoting factor. From these results, we propose that axonal regeneration occurs in axotomized peripheral nerves as a result of cytosolic reduced GAL-1 being released from Schwann cells and injured axons, which then becomes oxidized in the extracellular space. GAL-1/Ox in the extracellular space stimulates macrophages to secrete a factor that promotes axonal growth and Schwann cell migration, thus enhancing peripheral nerve regeneration and functional recovery. These results suggest that rhGAL-1/Ox may be a novel factor for functional restoration of injured peripheral nerves. [J Physiol Sci. 2008;58 Suppl:S36]

抄録全体を表示

Ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), and oncostatin M (OSM) belong to the Interleukin-6 cytokine family, and utilize the receptor subunit gp130 for initiating signal transmission. These cytokines are likely to promote neuronal survival and axonal regeneration after peripheral nerve injury, but molecular mechanisms how they act on neurons remain to be elucidated. In this study, recombinant CNTF, LIF, CT-1, and OSM (5-500 ng/ml) significantly enhanced survival and neurite outgrowth of cultured adult rat dorsal root ganglion (DRG) neurons. Among these recombinant proteins at the same concentration (50 ng/ml), CNTF showed the highest activity on the ratios of survival and neurite-bearing cells. By Western blot analysis, CNTF induced phosphorylation of signal transducer and activator of transcription (STAT) 3, Akt and extracellular signal regulated kinase (ERK) in the neurons. The neurite outgrowth-promoting activity of CNTF was diminished by co-treatment with 5-25 μM of Janus family of tyrosine kinase (JAK) 2 inhibitor AG490, 25-50 μM of phosphatidyl inositol-3'-phosphate-kinase (PI3K) inhibitor LY294002, or 50 μM of mitogen-activated protein kinase kinase (MEK) inhibitor PD98059. Its survival-promoting activity was also affected by AG490 and LY294002, but not by PD98059. These findings suggest that JAK2-STAT3, PI3K-Akt and MEK/ERK signaling pathways are involved in the CNTF-induced neurite outgrowth in mature DRG neurons, whereas the former two pathways may play major roles in mediating the survival response of neurons to CNTF. [J Physiol Sci. 2008;58 Suppl:S36]

抄録全体を表示

Diabetic neuropathy is the most common complication of diabetes mellitus. Many patients with neuropathy have various forms of symptoms, including hyperalgesia and spontaneous pain. Although the mechanisms by which such neuropathic symptoms develop remain unclear, the increased spontaneous activity of dorsal root ganglion (DRG) neurons has been proposed to cause hyperalgesia in diabetes. The voltage-gated ion channels are essential for the initiation and propagation of action potentials in many excitable cells. Among them, the voltage-dependent sodium/calcium channels are highly expressed in the somata of small DRG neurons, previous workers have investigated the alteration of activities of these channels in association with pathogenesis of diabetic neuropathy. To clarify the mechanism of painful diabetic neuropathy, we examined the tetrodotoxin-resistant sodium current (TTX-R I_Na) and intracellular calcium concentration in isolated small DRG neurons from control and diabetic rats. We found that the TTX-R I_Na in diabetic DRG neurons was enhanced in amplitude and was activated at more negative potentials compared with that in control neurons, and we also found that the duration of calcium transients induced by high extracellular K⁺ in small DRG neurons was significantly prolonged compared with that in control neurons. These results suggest that both sodium and calcium channels play important roles in the pathogenesis of painful diabetic neuropathy. [J Physiol Sci. 2008;58 Suppl:S36]

抄録全体を表示

Various factors have been implicated in the pathogenesis of diabetic neuropathy such as oxidative stress, polyol pathway hyperactivity, abnormality of Protein kinase C activities and glycation. These glucose-mediated metabolic abnormalities affect all components of nerve tissue including neurons and Schwann cells. Oxidative stress has been considered as major pathogenesis of diabetic neuropathy. To investigate the effects of glucose and a novel antioxidant, resveratorl, on apotosis, dorsal root ganglion (DRG) neurons were isolated from embryonic Sprague-Dawley rats. High glucose for 24 h significantly increased TUNEL positive staining and this increase was ameliorated by resveratrol. Resveratrol increased antioxidant enzyme, NAD(P)H:quinone oxidoreductase-1 (NQO1) expression. These findings suggest that high glucose induced apotosis in neurons and that resveratrol prevented this apotosis via enhancing antioxidative defense mechanism. C-peptide has been demonstrated to have various physiological activities including insulinomimetic effects and recognized as the pathogenesis of type1 diabetic neuropathy. To investigate the effects of high glucose and C-peptide on proliferation activities, immortalized mouse Schwann (IMS32) cells were cultured with high glucose for 4 weeks. High glucose significantly inhibited [³H]-thimidine uptake. C-peptide ameliorated this decrease. Short incubation with C-peptide for 20 min increased phospho-ERK1/2 expression. These observations suggest that high glucose inhibited proliferation in Schwann cells and beneficial effects of C-peptide may be mediated, at least in part, through an amelioration of Schwann cell growth via activation of MAP kinase. [J Physiol Sci. 2008;58 Suppl:S37]

抄録全体を表示

We have previously established spontaneously immortalized cell lines from long-term cultures of normal adult mouse Schwann cells. Establishment of such Schwann cell lines derived from murine disease models may greatly facilitate studies of the cellular mechanisms of their peripheral nervous system lesions in the relevant diseases. We maintained long-term cultures of Schwann cells derived from dorsal root ganglia and consecutive peripheral nerves of Niemann-Pick disease type C mice (spm/spm, npcnih/npcnih), globoid cell leukodystrophy mice (twitcher), myelin P0 protein-deficient mice (P0-/-), neurofibromatosis type 1 gene (NF1)-deficient mice (Nf1Fcr/+), Sandhoff disease mice (HexB-/-), and Fabry disease mice (Gla-) for 8-10 months, and established spontaneously immortalized cell lines from all these animals. These cell lines showed spindle-shaped Schwann cell morphology and distinct Schwann cell phenotypes and retained genomic and biochemical abnormalities, sufficiently representing the in vivo pathological features of the mutant mice. We have been able to obtain these immortalized Schwann cell lines from mice of ICR, BALB/c, and C57BL strains, and it is likely that the spontaneous immortalization of long-term cultured Schwann cells is a general phenomenon in both normal (wild-type) and mutant mice. These immortalized Schwann cell lines can be useful in studies of nervous system lesions in these mutant mice and relevant human disorders. [J Physiol Sci. 2008;58 Suppl:S37]

抄録全体を表示

The LC has been implicated in the sleep/wake cycle, attention/alertness, emotional/stress responses, and cognitive processes. In order to make clear the functions of the LC, we developed a novel method to destroy selectively the NA neurons in the LC. Transgenic mice were used that expressed human interleukin 2 receptors (hIL2R) driven by the dopamine-beta hydroxylase (DBH) promoter. One week following stereotaxic microinjection of the immunotoxin (anti-hIL2R antibody conjugated with Psudomonas exotoxin) into the LC of a transgenic mouse, the cell bodies in the LC disappeared totally together with the disruption of NA nerve terminals in the projection fields. No signs of recovery of the ablated LC neurons were noted 4 weeks following immunotoxin injection. The LC-ablated mice spent more time in the open arms in the elevated plus-maze, showed central field preference in the open-field, and buried less number of marbles in the marble burying test, suggestive of the role of the LC in determining the anxiety state of mice. In contrast, plasma ACTH was not significantly different in such stress paradigms as restraint and the immune challenge with LPS injection, suggesting that LC may not play an essential role in transmission of the stress signals to the hypothalamus. Thus, a novel method was developed for selective and thorough destruction of the LC by the immunotoxin-mediated cell targeting, and differential involvements of the LC were disclosed in the anxiety-related behaviors and neuroendocrine stress-responses. [J Physiol Sci. 2008;58 Suppl:S37]

抄録全体を表示

To define the function of Oxytocin receptor (OXTR) in vivo, we generated mice deficient in Oxtr gene (Oxtr-/-). Oxtr-/- mice showed no obvious defect in fertility or reproductive ability, however they showed several aberrations especially in their social behaviors such as male aggression, maternal behaviors and mother-offspring interaction. In addition, they also showed novel physiological dysfunctions caused by deficit of Oxtr gene, such as male specific obese and abnormal control of body temperature when they were exposed to cold. Similarly, slight obese in male and abnormal control of body temperature, when exposed to cold, was also observed in mice deficient in ligand Oxytocin (Oxt) gene. Recently, we newly generated Oxtr-Venus knock-in mice as a new tool to characterize the neurons expressing Oxtr and to further study the distribution of them in brain. We detected Venus-positive neurons at many nuclei, which were though to be involved in centers controlling social behaviors and temperature homeostasis. Moreover, administration of Oxytocin into median laphe, where many Venus positive neurons were detected, induced an increase of body temperature. These findings imply that Oxytocin/Oxytocin receptor system not only control social behaviors but also energy and temperature homeostasis. [J Physiol Sci. 2008;58 Suppl:S38]

抄録全体を表示

Corticotropin-releasing factor (CRF) plays a key role in stress responses such as changes in the endocrine system, autonomic nervous system, behavior and mood. The various actions of CRF are induced through two subtypes of CRF receptor: the CRF-R1 and the CRF-R2, with a higher affinity to CRF-R1 than to CRF-R2. Urocortins 2 (Ucn 2), one of CRF family peptides, is thought to be an endogenous ligand for CRF-R2. We previously demonstrated that Ucn 2 is expressed in the POMC cells of rat pituitary, and that the concentrations of Ucn 2 in culture media of rat anterior pituitary cells are extremely low compared with those of ACTH. We also showed that the mRNA expression and secretion of Ucn 2 in rat anterior pituitary are regulated positively by CRF and negatively by glucocorticoids. Since CRF-R2 has been shown to be expressed on gonadotrophs of the anterior pituitary, we hypothesized that pituitary Ucn 2 may control the expression and secretion of gonadotropin.. Monolayer culture of rat anterior pituitary cells showed that the secretion of LH and FSH was suppressed by Ucn 2. Anti-sauvagine 30 and anti-Ucn 2 antibody (SR6) up-regulated LH and FSH secretion and their β chain mRNA expression. Intraperitoneal injection of SR6 in male rats significantly increased LH and FSH secretion and their mRNA expression compared with those in control rats. These results suggest that pituitary Ucn 2 is involved in the regulatory mechanism of the expression and secretion of gonadotropin through its tonic and inhibitory action on gonadotrophs in a paracrine manner. [J Physiol Sci. 2008;58 Suppl:S38]

抄録全体を表示

Emotional responses are thought to play a vital role in survival and in our ability to adapt to our environment. It has been suggested that cognition is the most important component among the response in human. However little is known about cognition for emotional events in the brain. From these standpoints, we have done neuroimaging analyses to explore human emotional responses in the brain used by a functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in healthy volunteers and psychiatric patients. At first, to investigate which areas of the brain play an important role in the perception of stressful event and the emotional response, we performed a functional magnetic resonance imaging (fMRI) study in patients with eating disorders (ED) that involved recognition of unpleasant words concerning body image. Our results showed that the amygdala and MPFC played an important part in processing unpleasant words concerning body image in ED. Secondly, We studied the neural activation associated with anticipations of emotional pictures using fMRI and MEG in healthy volunteers and patients with major depression. Our results suggested a top-down modulation from anterior brain regions of the network, which includes the anterior cingulate cortex, ventrolateral prefrontal cortex (VLPFC), insula, and amygdala, to visual cortex during certain negative anticipation. Moreover, in depressive patients compared to healthy controls, VLPFC was more activated during certain negative anticipation. These findings suggest the important role of certain negative anticipation in emotional responses. [J Physiol Sci. 2008;58 Suppl:S38]

抄録全体を表示

Venous stasis caused by combined effects of immobility and an increased gravitational pressure gradient between the heart and lower limbs is an important risk factor for deep venous thrombosis (DVT) in long-haul air travel. Accordingly, the effects of sitting posture on lower limb hemodynamics have been a matter of great interest, and it was found that the popliteal venous flow velocity was decreased to 20% and the cross-sectional area was increased to 500% by posture change from prone to sitting, while the flow volume (flow velocity × cross-sectional area) was not altered. Devices and/or maneuver that increase the venous flow velocity are thought to be effective for reducing venous stasis. An ottoman-type (business class) seat significantly improved the flow velocity and cross-sectional area of the popliteal vein. Muscle contraction induced by neuromuscular electrical stimulation of the gastrocnemius (NMES) also improved the venous flow velocity; however the cross-sectional area was not affected by NMES. Furthermore, combination of graduated compression stocking and NMES significantly improved lower limbs hemodynamics of bed-ridden patients; the effect was comparable with intermittent pneumatic compression, which is commonly used as a prophylaxis of DVT. These results indicate that immobility and an increased gravitational pressure gradient are the major factors for lower limbs venous stasis; upgrade a seat to a business class and/or muscle contraction are effective for improving venous stasis. [J Physiol Sci. 2008;58 Suppl:S39]

抄録全体を表示

Vascular endothelial cells (VECs) and blood components coordinate to maintain blood fluidity and flow. High expressions of anti-coagulatory factors as well as profibrinolytic proteins are essential for VECs to prevent thrombus formation. Heparan sulphate, a cofactor for anti-thrombin, and thrombomodulin, a modifier of thrombin's function from coagulatory to anti-coagulatory, as well as prostacyclin and NO are representative anti-coagulatory factors. Tissue plasminogen activator (tPA) is the representative of pro-fibrinolytic protein. Impairment of these function and/or expression of other thrombogenic factors, in turn, initiates thrombotic disorders, which are frequently seen in inflammation, mental stress, and metabolic syndrome. Tissue factor, an initiator of coagulation, and PA inhibitor 1 (PAI-1), a specific tPA inhibitor, are known to be expressed in VECs only under pathological conditions and trigger thrombosis. In blood, several factors including fibrinogen and PAI-1 also increase under certain pathological condition, which increases the risk for thrombosis. In this symposium, we discuss how VECs and blood components function to maintain blood fluidity, and how thrombosis event is initiated when these mechanisms are impaired [J Physiol Sci. 2008;58 Suppl:S39]

抄録全体を表示

Venous thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE). It was recently reported that the mortality rate from PTE markedly increased for the last 5 decades. Furthermore, it was demonstrated that the incidence of DVT in Japan was almost same as that in western country in patients with total hip replacement or total knee replacement surgery. Dr. Virchow reported a century ago that three general changes caused thrombosis; changes in the vessel wall, changes in the blood flow and changes in the blood composition. These changes are called as Virchow's triad. An abnormality in Virchow's triad is involved in the pathophysiology of DVT. The stasis, changes in endothelial function and/or activation of pro-coagulant activity induce venous thrombosis. Unlike an artery, vein has venous valves. Venous valves guide the direction of blood flow and prevent regurgitation, and subsequently return blood to heart from peripheral region against gravity. Venous thrombosis in the lower limbs typically occurred in the valve pockets. At the valve pockets, decreased shear stress and increased hypoxia are observed and they induce venous thrombosis. The venous thrombus generated from the valve pocket does not attach to the vessel wall and this venous thrombus is released. Then the thrombus reaches to pulmonary artery, and pulmonary embolism is subsequently occurred. Sudden death after long flight, certain surgical operation or long bed-rest may be due to this pulmonary embolism. Therefore, the prevention of DVT is important. [J Physiol Sci. 2008;58 Suppl:S39]

抄録全体を表示

The incidence of pulmonary embolism is recently increasing in Japan. Pulmonary embolism occurs mainly on the basis of deep vein thrombosis, and these conditions could be considered as the continuum of venous thromboembolism. Venous thromboembolism is traditionally considered to be relatively rare in Japan, as there are no specific congenital thrombophilia such as factor V Leiden. A recent increase in venous thromboembolism seems to attribute to the acquired thrombotic tendency in relation to the transition of the life style. Clinically, early and accurate diagnosis is critically important because of the high mortality rate from pulmonary embolism and the large number of cases not diagnosed before causing death. Over the last decade, diagnostic and therapeutic strategies have been changed. The integrated strategies based on clinical risk evaluation, D-dimer, and multi-row detector computed tomography scans result in safer, more convenient and cost-effective diagnosis with high sensitivity and specificity. As well as antigocagulation using heparin, interventions such as thrombolysis and placement of inferior vena cava filter are reserved for special situations. Early detection of deep vein thrombosis and thromboprophylaxis using low-molecular-weight heparin or pentasaccharide (fondaparinux), factor Xa inhibitor in high-risk patients would achieve more effective prevention of pulmonary embolism. [J Physiol Sci. 2008;58 Suppl:S40]

抄録全体を表示

Loss-of-function and gain-of-function studies have demonstrated that genes encoding Wt1, Ad4BP/SF-1, Emx2, and Lhx9 are required for gonad development, while genes encoding Sry, Sox9, Wt-1, M33, Dax-1, Fgf9, Arx, Wnt4, and Dhh exert their functions during the process of gonad sex determination/differentiation. Although these studies largely contributed to identify the components essential for gonad differentiation and/or gonad sex determination, functional relation between the components has remained to be elucidated. Our recent studies have been focused on this subject to realize the genetic program involved in gonad differentiation. Gain-of-function and loss-of-function studies with mice and chick embryos have been undertaken, and these studies revealed that Ad4BP/SF-1 is localized at the downstream of M33, Emx2, PITX2, and retinoic acid, and these regulations appears to be implicated in gonadal development through accelerating cell cycle progression. In addition, genetic studies demonstrated that M33 is localized at the upstream of Sry and Sox9 involved in testicular development. Although these studies indicated genetic correlations between the genes, it still remains elusive whether these correlations are direct or indirect. To determine it, we have performed in vivo transgenic analyses of the promoter function of Ad4BP/SF-1 and in vitro biochemical studies of the transcription factors. These studies help us understand the genetic program of gonad development and gonad sex differentiation. [J Physiol Sci. 2008;58 Suppl:S40]

抄録全体を表示

Mammalians represent a extreme example of sex-divergence in the gamete production: while a human female produce a small number of eggs of around 500, spermatogenesis in male is highly productive and more than 10¹² sperms are born during a man's life. This high-throughput spermatogenesis is ensured by a potent stem cell system, while mammalian females seem not depend on obvious stem cell system. The mammalian spermatogenic stem cell system involves a specified microenvironment, the niche, for proper functioning of the stem cells. However, although functionally evidenced, nature of the niche remains mostly unknown. We have previously identified ngn3 (neurogenin3) as a specifically expressed gene in undifferentiated spermatogonia (A_undiff), the small germ stem/progenitor cell population in the mouse testis. GFP labeling allowed the detailed observations of this population without fixation and staining. Adding to that, a time-lapse system has been developed to observe the GFP-positive A_undiff behaviors in the living adult testes. Such observations revealed biased localization of A_undiff with strong relationship to the interstitial cells and blood vessels that surround the tubules. Upon transition into differentiating spermatogonia, they spread out of the restricted original regions to all over the tubules. Finally, alteration of the vasculature pattern is accompanied with the relocation of A_undiff. These observations provides a novel view for the structural basis of the stem cell niche in mammalian spermatogenesis, which may be based on a flexible strategy distinct from organisms with highly polarized gonads. [J Physiol Sci. 2008;58 Suppl:S40]

抄録全体を表示

The gonadal steroid estrogen plays a major role in the regulation not only reproductive behaviors such as sexual, aggressive and parental, but also an array of emotional and anxiety-related behaviors in both sexes, by acting through intracellular estrogen receptor (ERs), ligand dependent transcription factors. Our previous studies using single knockout mice for each of two types of ER genes, ER-α or ER-β, as well as double knockout for both genes revealed that a lack of ER activation might affect sex-specific expression of a number of emotional and social behavior. In the first part of the presentation, we will discuss the results of our studies focusing on differential roles of two types of ERs in the regulation of behavioral expression and possible brain mechanisms. In the second part, we will discuss the studies using aromatase knockout (ArKO) mice, in which synthesis of estradiol from testosterone is disrupted. ArKO mouse is a great model to study the roles of organizational and activational action of estradiol in development of sex-specific behavioral expression. We will present our most recent studies on the roles of estrogen stimulation in the determination of sex differences in emotional responses in novel environment and various social behavior as well as neuroanatomical characteristics in the limbic brain areas. (Supported by KAKENHI 17330151 and 17052001 to SO) [J Physiol Sci. 2008;58 Suppl:S41]

抄録全体を表示

The critical function of Oxytocin and Oxytocin Receptor was well known to stimulate uterine contraction in parturition and eject milk for feeding pups. Recent publications also showed the critical role of Oxytocin Receptor (OXTR) expressed in brain on regulation of wide-spectrally physiological and behavioral functions. Our study using mice defect in ligand Oxytocin and its Receptor (Oxytocin Receptor) genes showed essential roles of them on suppression of the aggressiveness of male mice to be the level as well as that of the WT animals. In contrast, although OXTR-/- female mice displayed impaired nurturing behavior, including pups retrieving and crouching over behaviors, OXT-/- female mice, even born form breeding pairs of the null parents did not. To further study in details about the physiological function of neurons expressing OXTR and to obtain clue to explain these discrepancy in mechanism establishing male and female social behaviors, we newly generated OXTR-Venus knockin mice. It could contribute to clearly locate the OXTR expressing neurons (OXTR neurons) in even live brain slice of the mice. We will also show a preliminary data about the discrepancy in distribution of the neurons expressing OXTR at PVN and SON of the hypothalamus in males and in milk feeding females. [J Physiol Sci. 2008;58 Suppl:S41]

抄録全体を表示

A ubiquitous property of vertebrates is fluctuation of locomotor activity over the 24 h circadian cycle. It is also known that birds as well as other vertebrates exhibit a clear sex difference in locomotor activity. In particular, locomotor activity of males is much higher than that of females in Japanese quail. Only males exhibit marked diurnal changes in locomotor activity. Based on a series of experiments using Japanese quail, here we show that 7α-hydroxypregnenolone, a newly discovered avian neurosteroid, is a key factor inducing sex-dependent locomotor activity. We first identified 7α-hydroxypregnenolone in quail brain by using biochemical techniques. This neurosteroid has not previously been described in avian brain. We then demonstrated that 7α-hydroxypregnenolone acutely increased quail locomotor activity. Subsequently, we demonstrated a clear sex difference in 7α-hydroxypregnenolone synthesis in quail. Both 7α-hydroxypregnenolone synthesis and locomotor activity in males were much higher than in females. Only males exhibited marked diurnal changes in 7α-hydroxypregnenolone synthesis, and these changes occurred in parallel with changes in locomotor activity. In contrast, females showed constantly lower levels of 7α-hydroxypregnenolone synthesis and locomotor activity. Thus, the novel avian neurosteroid 7α-hydroxypregnenolone may be a key factor inducing sex-dependent locomotor activity. This is the first demonstration in any vertebrate of a clear sex difference in neurosteroid synthesis. [J Physiol Sci. 2008;58 Suppl:S41]

抄録全体を表示

Classically, feeding is regulated by an alternation between "hunger" signals, which activate specific hunger centres in the hypothalamus, and "satiety signals", which include both circulating factors (such as plasma concentrations of leptin and insulin) and neurally-mediated signals from the gastro-intestinal tract. One important satiety signal is the brain-gut peptide cholecystokinin (CCK). Peripheral CCK acts on afferent nerve fibres of the gastric vagus nerve, these vagal neurons project to the caudal brainstem, where they activate neurons that project to hypothalamic nuclei involved in appetite regulation. In particular, peripheral injections of CCK activate neurons in the nucleus tractus solitarii and ventrolateral medulla, including specific subpopulations of the noradrenergic neurons of the A1 and A2 cell groups. We have shown that neurons in the nucleus tractus solitarii that express prolactin-releasing peptide (PrRP) are activated rapidly by food ingestion. Blockade of PrRP signalling increased food intake and attenuated CCK-induced anorexia. All these data suggest that PrRP is a central satiety signal that mediates the peripheral satiety signal, CCK. [J Physiol Sci. 2008;58 Suppl:S42]

抄録全体を表示

Classically, feeding is regulated by an alternation between "hunger" signals, which activate specific hunger centres in the hypothalamus, and "satiety signals", which activate specific satiety centres. How these signals are processed depends on the internal state of the animal, reflecting varying motivational drives, and is sensitive to diverse environmental cues, including those arising from photoperiod. An example of the complex motivational effects on appetite regulation is the mutually-exclusive nature of feeding behaviors and sexual behaviors. For all animals, the most important drives are to eat and to reproduce. As it is important that each is satisfied efficiently and effectively, animals commit their behavior to achieving either sex or food, rather than risk being both hungry and frustrated by failing to give their undivided attention to either goal. As a well-fed animal may be better able to compete for a mate and then to copulate with sustained enthusiasm, the first priority of hungry animals is to eat, and when sated they turn to sex. This seems to be achieved by a reciprocal regulation of sexual and ingestive behaviors, in which, for mammals, hypothalamic oxytocin appears to play an important part. Here, we will discuss evidence that the anorexigenic peptide alpha MSH released from neurons in the arcuate nucleus, acts on MC4 receptors expressed by oxytocin neurones in the hypothalamus to stimulate central release of oxytocin. Both alpha MSH and oxytocin are potent stimulators of male sexual arousal, and we will discuss evidence that this central release of oxytocin mediates these effects of alpha MSH [J Physiol Sci. 2008;58 Suppl:S42]

抄録全体を表示

We have identified gene expression changes in the paraventricular nucleus (PVN) and subfornical organ (SFO) of adult male Sprague Dawley rats following food or water deprivation. We interrogated Affymetrix microarrays with targets derived from the PVN or SFO of control, 2 day food deprived or 3 day dehydrated rats, and identified transcripts that are significantly up- or down-regulated a consequence of these stresses (Welsh t-test, p<0.05, n=5, with Benjamini-Hochberg multiple test correction and an arbitrary 2-fold change cut-off). Of the 127 transcripts that alter their expression in the PVN following dehydration, only 8 are also regulated in the SFO, out of a total of 259. In contrast, 900 genes are regulated in both the PVN and SFO by fasting, out of totals of 3515 and 1805 respectively. In the SFO, 234 transcripts alter in abundance with both dehydration and starvation, whilst 43 are similarly regulated in the PVN. Whilst most transcripts are similarly up- or down-regulated by both stimuli, some are regulated in the opposite direction–in the PVN, the gonadotrophin inducible transcription factor 1 (Giot1) mRNA is up-regulated by dehydration, but is apparently down-regulated by starvation. These data reveal that the physiological challenges of food and water deprivation result in clear and specific changes in gene expression in the PVN and SFO. We suggest that these changes may contribute to the integrated autonomic and neuroendocrine responses to these stressors. [J Physiol Sci. 2008;58 Suppl:S42]

抄録全体を表示

There are several lines of evidence suggesting that the AMP-activated protein kinase (AMPK) signaling pathways in the hypothalamus are involved in the regulation of energy balance. The phosphorylation of AMPK increased in the hypothalamus under the fasted condition, and the constitutive-active AMPK reportedly increased food intake and body weight. Furthermore, several peripheral signals related to energy balance are shown to affect the AMPK signaling in the hypothalamus. On the other hand, we reported previously that ghrelin and insulin, representative orexigenic and anorexigenic hormones, respectively, affected neuropeptide Y (NPY) gene expression in the arcuate nucleus only in the presence of glucocorticoids, suggesting that glucocorticoids play a permissive role in the regulation of NPY gene expression. To elucidate the relationship between glucocorticoids and AMPK signaling, we examined the effects of glucocorticoids on the expression of NPY and agouti-related peptide (AGRP) as well as phosphorylated AMPK (p-AMPK) in the hypothalamic organotypic cultures. The incubation with dexamesasone (DEX) increased the expression levels of p-AMPK in the explants, accompanied by significant increases in NPY and AGRP gene expression in the arcuate nucleus. The addition of compound C to the medium, which blocked the increase in the expression of p-AMPK by DEX, significantly attenuated NPY and AGRP expression stimulated by DEX. These data suggest that the AMPK signaling pathway is downstream of glucocorticoids to increased NPY and AGRP gene expression in the arcuate nucleus. [J Physiol Sci. 2008;58 Suppl:S43]

抄録全体を表示

As well as profound effects on food intake, the metabolic peptides, orexin and neuropeptide Y (NPY) stimulate the hypothalamo-pituitary-adrenal (HPA) axis. In late pregnancy the HPA axis is less responsive to central orexin-A. Orexin signals to the HPA axis, in part, via arcuate nucleus NPY neurons. We investigated HPA axis responses to NPY in pregnancy. Pregnant (d21) and virgin rats were blood-sampled before and after NPY (5μg, i.c.v.) or vehicle. Food intake was monitored. Rats were decapitated 4h after NPY for quantification of corticotropin releasing hormone (CRH)/arginine vasopressin (AVP) mRNA expression in the paraventricular nucleus (PVN). NPY increased ACTH (4-fold) and corticosterone (2-fold) secretion in virgin rats, but had no such effect on ACTH in pregnant rats, whilst the corticosterone response was markedly attenuated. Furthermore, NPY increased PVN CRH and AVP mRNA expression only in virgin rats. NPY increased food intake similarly in both virgin and pregnant rats. To explore a role for endogenous opioids in restraining HPA axis responses, we repeated the above experiment in the presence of naloxone (opioid antagonist; 5mg/kg i.v.). Naloxone did not alter HPA axis responses to NPY in virgin rats, however restored a HPA response in the pregnant rats. Thus, neuroendocrine stress responses to central NPY are absent in late pregnancy, while behavioural responses are intact. This explains suppressed HPA axis responses to orexin-A in pregnancy. Adaptations in HPA axis responsiveness in pregnancy involve endogenous opioid mechanisms and should minimise energy expenditure. Support: BBSRC [J Physiol Sci. 2008;58 Suppl:S43]

抄録全体を表示

Centrally, the hypothalamic peptides oxytocin and alpha-melanocyte-stimulating hormone (α-MSH) have similar effects on various behaviour in rat; in particular, they are both potent inhibitors of food intake. During feeding, satiety centres in the hypothalamus are activated, especially the ventromedial hypothalamus (VMH), which contains a high density of oxytocin receptors.We showed that α-MSH stimulates oxytocin release from dendrites of supraoptic neurones. It is possible therefore that the appetite-inhibiting effects of α-MSH are, at least in part, mediated by dendritically-released oxytocin. If so, a likely target for oxytocin is the VMH. To investigate whether oxytocin affects the electrical activity of VMH neurones in vivo, I first aimed to identify the various types of VMH neurones by their electrical characteristics in vivo.In in vivo electrophysiological experiments, I expose the ventral surface of the brain and make extracellular recordings of single VMH neurons. So far, of 237 spontaneously active VMH neurones recorded, most (about 90%) are within 8 clearly distinct subpopulations of VMH neurones according to their distinctive, spontaneous firing patterns, such as the mean firing rate, and interspike-interval distribution. Each of these subpopulations is then further characterised by its responses to appetite-inhibiting peptide oxytocin and satiety-inducing peptide cholecystokinin (CCK). Surprisingly, CCK, although it potently inhibits feeding, has an inhibitory effect on most VMH neurones while oxytocin seems to either activate, or inhibit, or has no effect, depending on the neuronal subtype recorded. [J Physiol Sci. 2008;58 Suppl:S43]

抄録全体を表示

EGF family-ErbB receptor signaling plays crucial roles in heart development and preservation of adult cardiac function. Among the ligands for ErbB family receptors, neuregulin-1 (NRG-1) and heparin-binding EGF-like growth factor (HB-EGF) have been shown to be important for cardiac development. We have found that NRG-1 is a critical ligand for ErbB receptors on cardiomyocytes, whereas HB-EGF is for those on cardiac fibroblasts. In addition, the Grb2-associated binder (Gab) family proteins are remarkably phosphorylated upon NRG-1 stimulation in cardiomyocytes. To investigate the function of Gab family proteins, we depleted both Gab1 and Gab2 from the myocardium by crossing conventional Gab2 KO mice and conditional Gab1 KO mice (α-MHC-Cre mice crossed with Gab1^flox/flox). Double KO mice of Gab1 and Gab2 (DKO) exhibited cardiomyopathic features (reduced contractility and remarkable ventricular dilation ) with endocardial fibrosis, as demonstrated by echocardiography and histological analyses. Furthermore, the number of capillaries was decreased in the heart. Microarray analysis using DKO mice showed the lack of gene expression of Angiopoietin-1 (Ang1) in response to NRG-1. This lack of Ang1 release might account for endocardial fibrosis and decreased capillary number, because Ang1 is an endothelium-trophic factor. NRG-1 is released from endothelium of capillary and/or endocardium. Thus, Gab family proteins in the myocardium are essential not only for the maintenance of myocardium but also for the stabilization of capillary/endocardial endothelium in the postnatal heart. [J Physiol Sci. 2008;58 Suppl:S44]

抄録全体を表示

Prostaglandin E (PGE), a potent vasodilator, plays a primary role in the patency of the ductus arteriosus (DA), a bypass artery for fetal circulation. Genetic disruption of the PGE specific-receptor EP4, however, paradoxically results in patent DA (PDA) in mice. Here we examined the mechanisms why EP4 disruption caused PDA. We found that chronic EP4 stimulation significantly enhanced migration and hyaluronic acid (HA) production in rat DA. When HA production was inhibited, EP4-mediated migration was negated, indicating that HA is responsible for chronic EP4-mediated migration. Interestingly, acute stimulation of EPAC, another effector of cAMP, promoted DA smooth muscle cell (SMC) migration and organization of actin stress fibers. Using immature rat DA explants, we found that ICF was promoted by both PKA and EPAC stimuli. Furthermore, adenovirus-mediated HAS2 gene transfer was sufficient to induce ICF in EP4-disrupted DA explants where ICF was not developed. Accordingly, EP4-cAMP signals have two essential roles in DA development, vascular dilation and ICF. Activation of PKA pathway increased transcription of the HAS2 genes and thus HA production. The PKA-mediated HA accumulation promoted DA SMC migration, resulting in promoting neointimal cushion formation. On the other hand, EPAC acutely promoted DA SMC migration and thus ICF in rat DA. Herein, cAMP-downstream targets, PKA and EPAC, synergistically promote ICF in DA. Our results imply that selective stimulation of cAMP-dependent signal pathway serves as an alternative therapeutic strategy for PDA to the current one, i.e. inhibition of PGE signaling by cyclooxygenase inhibitors. [J Physiol Sci. 2008;58 Suppl:S44]

抄録全体を表示

Accumulating evidence suggests that circulating progenitors potentially contribute to vascular healing and remodeling. Although there is growing enthusiasm for therapeutic and diagnostic application of circulating progenitors, there are concerns that transplanted precursors or bone marrow-derived cells may participate in the pathogenesis of unfavorable diseases. Thus, it is warranted to clarify the molecular signaling that regulates the fate of circulating vascular progenitors. We examined various vascular lesions in bone marrow (BM) chimeric mice. A significant amount of α-actin-positive cells in the vascular lesions were derived from BM. BM-derived cells also participated in re-endothelialization of the luminal side and neovascularization in the adventitia. Contribution of BM cells to neointimal hyperplasia depends on the type of injury models. Peripheral blood mononuclear cells (PBMNCs) were collected from animals or patients and cultured in the presence of various cytokines. PBMNCs differentiated into SMC-like cells or endothelial-like cells in vitro depending on the cytokines in the medium. In contrast to media-derived SMCs, the PBMNCs-derived SMC-like cells expressed abundant MMP-9 and little collagen. Coronary risk factors and angiotensin receptor blockers significantly influenced the number of circulating PBMNCs that could differentiate into SMC-like cells or endothelial-like cells. Our findings suggest that BM cells can give rise to vascular progenitor cells that home at the damaged vessels and differentiate into SMC-like cells or endothelial-like cells, thereby contributing to vascular repair, remodeling, and lesion formation. [J Physiol Sci. 2008;58 Suppl:S44]

抄録全体を表示

The sympathetic nervous system is a major mechanism of regulating cardiac function. Norepinephrine released from the synaptic terminal binds to beta-adrenergic receptors on the cardiac cell membrane, leading to the activation of G protein and adenylyl cyclase. cAMP produced by adenylyl cyclase initiates a cascade of phosphorylation reaction within the cardiac myocyte, leading to increased cardiac contractility and rate. The heart is known to express two major adenylyl cyclase isoforms, namely type 5 and type 6 isoforms. Type 5 adenylyl cyclase is a major isoform in adult hearts while type 6 in neonatal hearts. From various in vitro and in vivo studies in recent years, using transgenic or gene-targeted models as well as newly developed selective regulatory compounds for such isoforms, it has been shown that the two isoforms may play opposite roles in regulating cardiac myocyte viability and thus function as shown under various pathophysiological conditions. Activation of the type 5 isoform leads to increased cardiac contractility while prolonged activation may deteriorate cardiac function through increased cardiac myocyte apoptosis. In contrast, activation of the type 6 isoform plays protective roles for the heart, which has been shown in various animal models with the type 6 gene transfer. Disruption of type 5 isoform is now shown to protect the heart from various pathophysiological stresses, and to increase longevity. We will discuss potential molecular mechanisms for such differences between the adult and the neonatal isoforms in the heart. [J Physiol Sci. 2008;58 Suppl:S45]

抄録全体を表示

Voltage-dependent K⁺ channels are classified into two categories, 'delayed rectifier-type' and 'rapidly-inactivating A-type'. A-type K⁺ channel plays an important role in the control of action potential threshold, frequency, and duration in smooth muscles, which possess relatively high membrane excitability such as colon, portal vein, ureter and vas deferens. We showed that Kv4.3L, a longer isoform of Kv4.3, predominantly contributes to A-type K⁺ channel α subunit in smooth muscles. Additionally, regulatory β subunits of Kv4 channels, which promote the trafficking of Kv4 channels to plasma membrane and also modulate their kinetics, have been identified as neuronal Ca²⁺-binding proteins (NCBPs) with high similarity to calmodulin (CaM). We also identified that KChIP1, KChIP3, and NCS-1 are the major components of NCBPs in vascular and visceral smooth muscles. CaM-dependent kinase II (CaMKII) slows the inactivation of A-type K⁺ currents in mouse colonic smooth muscle cells. Similarly, autothiophosphorylated CaMKII slowed the Kv4.3 currents and affected the inactivation kinetics of Kv4.3 channels. In addition, the mutation of Ca²⁺-binding EF motif in KChIP did not affect the kinetics of Kv4 channels. Using site-directed mutagenesis, we suggested that CaMKII regulates A-type K⁺ current kinetics by direct phosphorylation of Kv4.3 at Ser550 on the C-terminus but not at Thr53 on N-terminus. [J Physiol Sci. 2008;58 Suppl:S45]

抄録全体を表示

A change in intracellular Ca²⁺ concentration is an important process for cardiac excitation-contraction coupling. Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has been identified as the one of the multifunctional and specialized proteins activated by cytoplasmic Ca²⁺ signaling in cardiomyocytes. Activated CaMKII targets several myocyte proteins such as Na⁺ channels, Ca²⁺ transport proteins (voltage-gated L-type Ca²⁺ channel, phosholamban and ryanodine receptor) and K⁺ channels, consequently controlling the membrane potential and modulating myoplasmic Ca²⁺ homeostasis. Recent studies have elucidated that cardiac adrenoceptor (AR) stimulation is one of the triggers for the activation of CaMKII. β-AR stimulation (which is the most prominent regulator of cardiac function) activates CaMKII by both a traditional Ca²⁺-dependent pathway (Gs-adenylyl cyclase-cAMP-PKA pathway) and by a more direct, Ca²⁺-independent pathway. Our recent finding is that α₁-AR stimulation also activates CaMKII as in the case of β-AR signaling. We reported that (1) CaMKII is activated by α_1A-AR-G_q-phospholipase C-l PKCs (δ and/or ε) pathway at transverse tubules and (2) activated CaMKII increases L-type Ca²⁺ current. In this presentation, we highlight the regulatory mechanisms of CaMKII activity by α₁-AR stimulation and show a novel model for CaMKII regulation of L-type Ca²⁺ channel function by α₁-AR stimulation. [J Physiol Sci. 2008;58 Suppl:S45]

抄録全体を表示

L-type Ca²⁺ channels have two opposing forms of autoregulatory feedback, Ca²⁺-dependent facilitation (CDF) and Ca²⁺-dependent inactivation (CDI). To explore the underlying mechanisms, we investigated the effects of CaM and CaMKII inhibitors on CDF and CDI with patch clamp technique in guinea-pig ventricular myocytes. We found that both CDF and CDI were depressed and finally abolished by CaM inhibitors, chlorpromazine (1-100 μM) and calmidazolium (1 μM). In contrast, CaMKII inhibitors, KN-62 (0.1-3 μM) and autocamtide 2-related inhibitory peptide (1 μM), delayed the development of CDF and CDI significantly, but did not depress both CDF and CDI. A CaM-binding GST-fusion peptide containing a. a. 1509-1791 of the C-terminal region of guinea-pig Cav1.2 (CT1) is prepared. In pull-down assay, CT1 treated with CaMKII shows a higher affinity for CaM than that treated with phosphatase. Conclusion: Both CaMKII phosphorylation and binding of CaM to the channel are involved in the process of CDF and CDI. We propose a hypothesis that CaM is a key molecule to bifurcate Ca²⁺ signal to CDF and CDI, while CaMKII plays a modulatory role. Acknowledgements: This work was supported by the grants from the Japan Society for the Promotion of Science and the National Natural Science Foundation of China (No.30670761). [J Physiol Sci. 2008;58 Suppl:S46]

抄録全体を表示

The inactivation of the cardiac L-type Ca²⁺ current is composed of voltage-dependent and calcium-dependent mechanisms. We modeled physiological modulation of inactivation of the current in cardiac ventricular myocytes. Firstly, we used the recent detailed kinetic data for voltage dependent-inactivation (VDI) and its modulation by β-adrenergic stimulation. We modeled VDI based on the experimental data and calcium dependent-inactivation (CDI) as a function of Ca²⁺-influx through L-type Ca²⁺ channels. This model could largely reproduce the behavior of physiological L-type Ca²⁺ channel current carried by divalent cations in the basal as well as under β-adrenergic stimulation. Next, we constructed microstructure based Ca²⁺ dynamics models to simulate Ca²⁺ influx through individual L-type Ca²⁺ channels and diffusion in the dyadic space which would induce CDI. These models used the agent base Monte Carlo method and they consisted of L-type Ca²⁺ channels with distal and proximal Ca²⁺ binding sites, dyadic space, sarcoplasmic reticulum membrane, and free calcium ions. The models reproduced major features of the CDI process which had been measured with single channel recording. The developed models will be useful to estimate the respective roles of VDI and CDI of L-type Ca²⁺ channels in various physiological and pathological conditions of the heart. [J Physiol Sci. 2008;58 Suppl:S46]

抄録全体を表示

Frequency-dependent acceleration of relaxation (FDAR) of both Ca²⁺ transient and twitch contraction is a pivotal mechanism for regulating cardiac contraction. The Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) has been suggested to be involved in the FDAR. So far several computer models were developed to examine how CaMKII activity is regulated by heart rate, but these were not directly based on experimental data of the cardiac isoform, CaMKIIδ or did not consider deactivation of CaMKII by phosphatases (PPs). To advance our understanding of the significance of CaMKII autophosphorylation and its regulation by PPs in heart, we developed a new mathematical model for CaMKIIδ. Since more experimental data were available for the neuronal CaMKIIα isoform, the model was first adjusted for the α isoform and then fitted to kinetic data of the δ isoform, which has a higher affinity for calmodulin and a higher autophosphorylation rate. Our simulation demonstrated that repetitive Ca²⁺ transients cumulatively increased a fraction of autophosphorylated CaMKIIδ in a manner dependent on beating frequency. Variation in the PP activity was capable of modifying the CaMKIIδ activation level. These simulation results indicated that CaMKIIδ is cumulatively activated within a physiological range of heart rate and the PP activity effectively modulates the CaMKIIδ activity. [J Physiol Sci. 2008;58 Suppl:S46]

抄録全体を表示

A major source of excitatory drive to the preganglionic sympathetic neurons originates from the rostral ventrolateral medulla (RVLM). RVLM sympathetic premotor neurons (RVLM neurons) receive an indirect input from peripheral chemoreceptors. However, it is still unclear whether RVLM neurons have chemosensitivity or not. We studied if RVLM sympathetic premotor neurons respond to hypercapnic (8% CO₂)-hypoxia (5% O₂) and sodium cyanide using an in situ arterially perfused preparation (the working heart-brainstem preparation). We recorded activities of the thoracic sympathetic chain and RVLM neurons. Finding that RVLM neurons continued to fire after switching to a low Ca²⁺ (0.2 mM)-high Mg²⁺ (5.25 mM) perfusate to block synaptic transmission is consistent with the hypothesis that they may have intrinsic pacemaker activity in absence of synaptic inputs. Since RVLM neurons were activated by hypercapnic-hypoxia and sodium cyanide after blockade of synaptic transmission, they may be directly sensitive to hypoxia and sodium cyanide. This study suggested that RVLM neurons can play a role of the central oxygen sensor and directly regulate the circulation of the blood according to the central oxygen level. [J Physiol Sci. 2008;58 Suppl:S48]

抄録全体を表示

We have reported that baroreflex bradycardia evoked by stimulating the aortic nerve is blunted at the onset of voluntary static exercise in conscious cats and spontaneous exercise in decerebrate cats, suggesting that central command may inhibit the arterial baroreceptors-heart rate reflex (Komine et al. 2003; Murata et al. 2004; Matsukawa et al. 2006, 2007). Although the interaction between central command and arterial baroreflex should occur within the lower brainstem, an underlying neural mechanism remained unknown. We hypothesized that endogenous release of nitric oxide in the brain played a role in inhibiting the cardiac component of arterial baroreflex at the onset of exercise. To test the hypothesis, we examined the effect of intracisternal injection of a nitric oxide synthesis inhibitor (L-NAME) on the blunted baroreflex bradycardia at the onset of spontaneous exercise in decerebrate cats. Arterial blood pressure (AP) was rapidly elevated by occluding the abdominal aorta above the level of the kidneys. The baroreflex bradycardia evoked by an increase in AP due to the occlusion was blunted at the onset of spontaneous active exercise and fictive exercise with muscle paralysis. The inhibition of baroreflex bradycardia at the onset of spontaneous exercise was attenuated by intracisternal injection of L-NAME, but not by D-NAME. Thus central command may cause an endogenous release of nitric oxide in the lower brainstem, which has a role in inhibiting the cardiac component of the arterial baroreflex. [J Physiol Sci. 2008;58 Suppl:S48]

抄録全体を表示

To study cardiac function of newborn small animals, it should be considered that they show freezing response and HR drop when they are held by our hands (Hofer & Reiser, 1969). In this respect, no basal HR of them has been obtained hitherto. A noninvasive measurement by using piezoelectric sensor without inducing the freezing response revealed for the first time the basal HR of freely-moving newborn mice (Sato, 2007). The HR increased in exponential-like curve from 320 to 670 (b/m) during the first two postnatal weeks and it was considerably higher than that reported previously by Cedrini and Rostagno (1985), in which mice might had been decreased their HR due to the freezing response induced by handling procedure. On the other hand, attaching ECG electrodes to the same mice induced freezing response and marked HR drop. Patterns of the HR drop during 5 min of recording shifted from constant decrease in HR (slow cardiodeceleration) at P0-3 to rappid HR drop followed by its recovery (transient bradycardia) at P9-14. Both patterns were observed at P4-8. Analysis of the patterns in HR drop by autonomic blockade suggests that the slow cardiodeceleration and the transient bradycardia is likely mediated by tonic sympathetic withdrawal and phasic parasympathetic activation, respectively, and that vagal control on HR matures in P4-9. Comparing HR responses to attaching ECG electrodes with noninvasive PZT readings may provide us a novel tool for investigating the development in autonomic control on HR of newborn small animals including baroreflex. [J Physiol Sci. 2008;58 Suppl:S48]

抄録全体を表示

Previous studies reported that rat heart begins to beat during embryonic day 9.5 (E9.5 day) and day 10.5 (E10.5 day). Several studies showed the increase in heart rate and the decrease in calcium transient duration during E10.5 day and adulthood. Few study, however, showed the change of heart rate and calcium transient during E9.5 day and E10.5 day. Therefore, we evaluated changes of beating area, heart rate and calcium transient around the time of the beginning of heart beat, especially from E9.5 to E10.5 day. Whole embryos were removed from uterus and then embryos were incubated in 37 °C Tyrode solution. The heart beat was observed using CCD camera system. Hearts at E10.0 day did not beat at removing from uterus and did not start to beat for 90 min. Hearts at E10.2 had already beaten (68.5/min). Hearts at E10.1 day did not beat at removing from uterus but started to beat in almost regular rhythm (31.3/min) within 90 min. Beating area of hearts at E10.1 day was firstly small and enlarged with time. Fluo-3 AM was used for observation of calcium transient. The calcium transient duration decreased with development. The change of calcium transient during E10.1 day and E10.5 day is similar to that during E10.5 day and adulthood. In conclusion, E10.1 day is the physiological period of the beginning of heart beat. [J Physiol Sci. 2008;58 Suppl:S48]

抄録全体を表示

Activation of ATP-gated receptor channels (P2X receptors) facilitates glutamate release and excites postsynaptic neurons in the nucleus of the solitary tract (NTS) (Shigetomi & Kato, 2004). The subtype of P2X receptor underlying this transduction of extracellular ATP signal to excitatory transmission enhancement remains unidentified. To address this issue, we analyzed the effects of agonists and antagonists of P2X on this release facilitation in brain slices. The following lines of evidence strongly argue for a possible involvement of P2X2/3 heteromeric receptors: (1)a P2X3-selective antagonist, A-317491 (3 μM), suppressed this facilitation, (2) space- and time-delimited ATP application with laser photoactivation of caged ATP induced rapid onset and persistent facilitation, (3) the release facilitation with αβmATP, in a manner sensitive to TNP-ATP (10 μM), was observed in mice lacking P2X4 subunits. As P2X2 subunits has been selectively localized on the primary afferent termini in the NTS, this conclusion implies that extracellular ATP-triggered glutamate release in the NTS could mimic vagal afferent signal in response to changes in the intracranial environment including astrocyte network excitation that could result in ATP release onto perisynaptic space. [J Physiol Sci. 2008;58 Suppl:S49]

抄録全体を表示

Recent studies have revealed that microglia play critical roles in neurodegenerative diseases, such as Parkinson disease, Alzheimer disease and Huntington disease. In the present study, we sought to determine the hypothesis that glucocorticoids may modulate microglial activation in animal model of Parkinson disease. The present study investigated microglial activation and dopaminergic neurodegeneration in substantia nigra pars compacta (SNpc) following acute MPTP treatment in sham-operated mice, adrenalectomized mice (ADX) and ADX plus corticosterone treated mice. The number of dopaminergic neuron was significantly decreased in ADX mice 7 days after MPTP treatment as compared to sham-operated mice. In addition, the enhanced microglial activation occurred in the SNpc in ADX mice as compared to that of sham group. Furthermore, the dopaminergic neurodegeneration as well as microglial activation was substantially recovered in ADX plus corticosterone treated mice. Thus, the present study indicates the possibility that glucocorticoids may inhibit microglial activation and dopaminergic neurodegeneration. [J Physiol Sci. 2008;58 Suppl:S49]

抄録全体を表示

Migration of microglia towards the lesion site plays an important role in the immune system in the brain. Under pathological/physiological conditions such as neuronal axotomy, inflammation, Alzheimer's disease, nociception, cognition, and eating behaviors, several neuropeptides are up-regulated and therefore may affect the brain immune system. In the present study, we investigated the effects of neuropeptides including bradykinin on microglial migration and their signal mechanisms. The bradykinin-induced migration of microglial cells was dependent on activation of protein kinase C, phosphoinositide 3-kinase, extracellular Ca²⁺ influx due to the reverse mode of Na⁺/Ca²⁺ exchanger, and activation of Ca²⁺-dependent K⁺ currents (I_K(Ca)). On the other hand, ATP, one of the chemoattractants for microglial cells, was dependent on G_i/o but not on I_K(Ca). These results suggest that ATP and neuropeptides induce microglial migration with distinct mechanisms and may have different role in their immune system under pathophysiological conditions. [J Physiol Sci. 2008;58 Suppl:S49]

抄録全体を表示

Neurodegeneration and gliosis may play important roles in kindling epileptogenesis. These changes have been analyzed mainly in hippocampus region and astrogliosis. However, the role of microgloisis in kindling is not very clear. In the present study, we analyzed the microglial activationin brain of kindled mice during and after seizure susceptibility formation. Microglia were stained by an antibody against ionized calcium-binding adaptor molecule (Iba 1) which is a specific marker protein for microglia. Iba 1 immunoreactivity was found to be highest at kindling stage of Clonus 2 and lowered at Clonus 5 in the thalamus and CA3 areas of hippocampus. The other areas such as the hilar part of dentate gyrus and periform cortex showed an increase of immunoreactivity with the progression of the kindling stage. These findings indicate dynamic changes in microglial activation in different kindling stages, and suggest that microgliosis may play a role in formation of new circuits in the brain following kindling. [J Physiol Sci. 2008;58 Suppl:S49]

抄録全体を表示

During food intake, acidic fibroblast growth factor is released from the ependymal cells responding to the increase in glucose from 2-3 to 4-6 mM in CSF. Also leptin increased in plasma enters into the brain. Both first invade into the hypothalamus and suppress food intake, then reach to the hippocampus and facilitate spatial learning and memory. We found recently the facilitation of learning and memory by the twice increased glucose alone in the brain. Namely, the injection of 0.2 ul of 6 mM glucose in the CA1 area in the hippocampus facilitated spatial learning and memory. In vitro experiments, glucose concentration in perfused solution was changed from 3 to 6 mM for 15 min. By this change, the presynaptic release of transmitters and postsynaptic responses for transmitters in CA1 neurons were significantly augmented. Neurochemically by this change significant facilitations of phosphorylations of presynaptic synaptin III and postsynaptic PKC, CaMKII, and extracellular signal-related regulated kinase were occurred. LTP of CA1 neurons was also significantly facilitated by this change with the increased phosphorylation of MARCKS (related to the brain plasticity). These all indicate the significance of food intake for the brain plasticity. [J Physiol Sci. 2008;58 Suppl:S50]

抄録全体を表示

We have studied the effect of chewing in the stress-induced suppression of hippocampal memory process, by measuring the long-term potentiation (LTP) on the hippocampal CA1 region of rats that underwent a restraint stress with or without chewing a wooden stick. Adult male rats were divided into three conditions: the restraint stress condition (stressed; ST), the voluntary chewing condition during the restraint state (chewing; SC), and the control condition without any treatments (control; CT). The rats in the SC group required 24 h to regain the stress-attenuated magnitude of LTP to the control level, while that in the ST group required 48 h. This sooner recovery of LTP in the SC group was associated with the larger number of functioning NMDA receptors, since bath-applied glycine augmented the LTP of both of the SC and ST groups at 24 h post-stress survival period to the level of the CT group with the same treatment. We also observed suppressed plasma level of adrenocorticotropic hormone in the SC group, showing 59% of that in the ST groups, at the end of the stress exposure. These findings suggest that chewing may suppress stress responses in the hypothalamic-pituitary-adrenal axis and the following corticosterone secretion, leading to the sooner recovery of hippocampal memory process. [J Physiol Sci. 2008;58 Suppl:S50]

抄録全体を表示

The central amygdaloid nucleus (CeA) receives projection from the The parabrachial nucleus (PBN) gustatory neurons and descendingly projects to the PBN. We have carried out neurophysiological and neuropharmacological experiments to assess whether the CeA is involved in modulating the gustatory activities of the PBN and the underlying mechanisms. The results showed that during CeA stimulation, the spontaneous activities of the taste neurons of PBN were depressed significantly(p<0.05) ,and the responses of the neurons to at least one effective taste stimulus of the four basic tastants were inhibited in most PBN neurons; Bilateral lesions of CeA facilitated the spontaneous discharges and the responses of PBN neurons to HCl and QHCl (P<0.01);Microinjection of 6-cyano-7-nitro-quinoxaline-2, 3-dione (CNQX), an AMPA receptor antagonist, into the CeA produced a time-dependent inhibition of the responses in 30% PBN taste neurons, with the responses to HCl and QHCl significantly lowered (P<0.05); After microinjection of bicuculline, a GABAA-selective antagonist, into the ipsilateral CeA , the responses of PBN neurons to four tastants all remarkably increased (P<0.01), respectively. However, after bicuculine was delivered into the contralateral CeA, the responses to NaCl, HCl and QHCl increased. These results not only support the involvement of the CeA in modulating gustatory activities of the PBN, but also provide clear evidences that the AMPA receptor and the GABAA receptor within the CeA are closely related to this modulation. [J Physiol Sci. 2008;58 Suppl:S50]

抄録全体を表示

This report deals with effects of intravenous or intra-portal injection of glycerol, a metabolic product of adipose tissue, on efferent activity of sympathetic nerve innervating white adipose tissue(WAT) of epididymis and afferent activity of hepatic branch of vagus nerve in anesthetized rats. 1) Intravenous injection (100ng-10microg) or intra-portal injection (10ng) of glycerol suppressed sympathetic nerve activity to WAT. 2) After sectioning of hepatic vagus nerve or right vagus trunk, iv injection of glycerol was showed no effect. 3) Intra-portal injection of glycerol (10ng) suppressed afferent nerve activity of hepatic branch of vagus nerve.Results of experiments suggest that hepato-portal glycerol sensors play a role as an input of negative feed-back circuit which suppress efferent activity of sympathetic nerve innervating WAT which in turn may suppress lipolysis. [J Physiol Sci. 2008;58 Suppl:S50]

抄録全体を表示

Hydrogen peroxide, one of the reactive oxygen species (ROS), induces pain when it is applied to skin. However, receptor of hydrogen peroxide is unknown. Transient Receptor Potential A1 (TRPA1) channel is activated by pungent compounds such as allylisothiocianate (AITC), cinnamaldehyde, allicin and low temperatures. Kwan et al and Bautista et al report that pain is depressed in TRPA1 knockout mice, indicating that TRPA1 is a receptor that induces pain. These results lead us to hypothesize that TRPA1 is a receptor of hydrogen peroxide. Using Ca⁺⁺ imaging and patch clamping, we aimed to verify this hypothesis. Hydrogen peroxide raised Ca⁺⁺ concentration in TRPA1-expressing HEK293 cells. TRPA1 inhibitors (ruthenium red and camphor) suppressed this response. Under voltage-clamp mode (-60mV), hydrogen peroxide induced inward current in TRPA1-expressing HEK293 cells. In inside-out patch membrane excised from TRPA1-expressing HEK293 cells, single-channel activity appeared in response to hydrogen peroxide. To investigate whether TRPA1 is activated by hydrogen peroxide in sensory neurons, we recorded Ca⁺⁺ imaging in cultured DRG neurons of mice. Most AITC-sensitive neurons were activated by hydrogen peroxide. We conclude that TRPA1 is a receptor of hydrogen peroxide. [J Physiol Sci. 2008;58 Suppl:S51]

抄録全体を表示

We investigated the role of tumor necrosis factor-α (TNFα) in activating the store-operated Ca²⁺ channels in CCD-18Co cells via the expression of canonical transient receptor potential (TRPC) channel isoforms. CCD-18Co cells were derived from human colon and exhibit many properties typical of intestinal subepithelial myofibroblasts, which play crucial roles in intestinal homeostasis, inflamation, and neoplasia. 24hr treatment with TNFα activated store dependent Ca²⁺ influx with increased expression of TRPC1 in CCD-18Co. Simultaneously, cyclooxygenase (COX)-dependent PGE2 production was significantly enhanced. Part of the production has been shown to be dependent on Ca²⁺. TNFα-induced PGE2 production was significantly augmented by siRNA knockdown of TRPC1.From these results, we suggest that myofibroblasts could be the important target of inflammatory cytokines in the colon. The sustained elevation of [Ca²⁺]i in CCD-18Co may serve as the essential mechanism to regulate PGE2 production in response to cytokines. [J Physiol Sci. 2008;58 Suppl:S51]

抄録全体を表示