Journal of Smooth Muscle Research
Online ISSN : 1884-8796
Print ISSN : 0916-8737
ISSN-L : 0916-8737
Volume 41, Issue 3
Displaying 1-5 of 5 articles from this issue
Invited Review
  • Kimio Sugaya, Saori Nishijima, Minoru Miyazato, Yoshihide Ogawa
    2005 Volume 41 Issue 3 Pages 117-132
    Published: 2005
    Released on J-STAGE: July 09, 2005
    JOURNAL FREE ACCESS
    The micturition reflex is one of the autonomic reflexes, but the release of urine is regulated by voluntary neural mechanisms that involve centers in the brain and spinal cord. The micturition reflex is a bladder-to-bladder contraction reflex for which the reflex center is located in the rostral pontine tegmentum (pontine micturition center: PMC). There are two afferent pathways from the bladder to the brain. One is the dorsal system and the other is the spinothalamic tract. Afferents to the PMC ascend in the spinotegmental tract, which run through the lateral funiculus of the spinal cord. The efferent pathway from the PMC also runs through the lateral funiculus of the spinal cord to inhibit the thoracolumbar sympathetic nucleus and the sacral pudendal nerve nucleus, while promoting the activity of the sacral parasymapathetic nucleus. Inhibition of the sympathetic nucleus and pudendal nerve nucleus induces relaxation of the bladder neck and the external urethral sphincter, respectively. There are two centers that inhibit micturition in the pons, which are the pontine urine storage center and the rostral pontine reticular formation. In the lumbosacral cord, excitatory glutamatergic and inhibitory glycinergic/GABAergic neurons influence both the afferent and efferent limbs of the micturition reflex. The activity of these neurons is affected by the pontine activity. There are various excitatory and inhibitory areas co-existing in the brain, but the brain has an overall inhibitory effect on micturition, and thus maintains continence. For micturition to occur, the cerebrum must abate its inhibitory influence on the PMC.
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Original
  • Krzysztof Jonderko, Anna Kasicka-Jonderko, Barbara Blonska-Fajfrowska
    2005 Volume 41 Issue 3 Pages 133-140
    Published: 2005
    Released on J-STAGE: July 09, 2005
    JOURNAL FREE ACCESS
    In a study aimed to test the effect of body position on the parameters derived from surface electrogastrograms, 17 healthy volunteers (2M, 15F; median age 22.5 years) attended in random order two examination sessions held on separate days. A 30-min recording of the interdigestive gastric myoelectrical activity (GMA) was followed by a 90-min postprandial recording after intake of a 394 kcal mixed solid-liquid test meal. For the first exanination the subject was examined in a recumbent position, whereas for the second exanination a sitting position was maintained. The dominant frequency and relative time occupied by normogastria was negligibly affected by the posture of the subject during GMA recording. However, a decrease in the dominant power (DP) of the gastric slow waves was observed during both the interdigestive and the postprandial recording period in a sitting position compared to a recumbent position. Consequently, the fed to fasted state DP ratio remained unaffected by body posture during GMA recording. The results indicate that by carefully observing procedural guidelines, good quality electrogastrograms can be obtained with a sitting subject, enabling the provision of comparable parameters to those achieved from standard examination in a recumbent position.
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  • Tadashi Nakagawa, Hiromi Misawa, Yoshiyuki Nakajima, Miyako Takaki
    2005 Volume 41 Issue 3 Pages 141-151
    Published: 2005
    Released on J-STAGE: July 09, 2005
    JOURNAL FREE ACCESS
    It is well known that the enteric nervous system plays a key role in the generation of gastrointestinal peristaltic movements. Recently, the networks of interstitial cells of Cajal (ICC) have been found to be essential in the generation of spontaneous gastrointestinal movements. However, the role of ICC in the mechanisms involved in the generation of peristaltic movements is still controversial. The aim of the present study was to reveal how pacemaker myenteric ICC (ICC-MY) and the enteric nervous system contribute to the mechanisms involved in the generation of intestinal peristalsis. We compared spontaneous peristaltic movements of the ileum in wild type (WT) mice with those in W/WV mutant mice which are selectively deficient in ICC-MY. Simultaneous recordings were made from both the circular and longitudinal muscle of a 4-cm long segment of ileum under hydrostatic pressure of 0-0.5 cm H2O. Mechanical activity and continuous video-images of the ileum were compared between WT and W/WV mutant mice under control conditions, in the presence of N-nitro-L-arginine methyl ester (L-NAME) and after tetrodotoxin (TTX). In the WT mouse ileum, peristaltic waves to propagate from the oral to the anal end were frequently observed. The frequency of these peristaltic waves and their associated synchronous longitudinal and circular muscle contractions was increased by L-NAME. The peristaltic waves were abolished by TTX. In the W/WV mutant mouse ileum, no peristaltic waves to propagate from the oral to the anal end were observed in control and even after L-NAME, although the local spontaneously generated longitudinal and circular muscle contractions were enhanced by L-NAME. These local contractions were not abolished by TTX. The results presented here suggested that ICC-MY are essential for the generation of spontaneous intestinal peristaltic movements. It is conceivable that ICC-MY may determine the polarity of the excitation of the intestine such that longitudinal and circular muscle contractions propagate from the oral to the anal end of the intestinal segments, although the question of why ICC-MY are necessary for the neural pathways remains unresolved.
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  • Yoshio Tanaka, Yoko Yamashita, Takahiro Horinouchi, Katsuo Koike
    2005 Volume 41 Issue 3 Pages 153-161
    Published: 2005
    Released on J-STAGE: July 09, 2005
    JOURNAL FREE ACCESS
    The β-adrenoceptor subtype that mediates adrenaline-induced relaxation was pharmacologically identified in smooth muscle cells of the isolated guinea-pig trachea. Adrenaline produced a concentration-dependent relaxation with a pD2 value of 7.1. The concentration-response curve for adrenaline was shifted rightwards in a competitive fashion by the β1-/β2-nonselective antagonists propranolol and bupranolol, with pA2 values of 8.85 and 8.97, respectively. Adrenaline-induced relaxation was not affected by the β1-selective antagonists atenolol and CGP-20,712A within the concentration ranges supposed to antagonize the β1-subtype (atenolol, ≤ 10-6 M; CGP-20,712A, ≤ 10 -8 M). By contrast, the concentration-response curve for adrenaline was shifted rightwards in a competitive fashion by atenolol at concentrations ≥ 3 × 10-6 M with a pA2 value of 5.77. The concentration-response curve for adrenaline was also competitively antagonized by the β2-selective antagonists butoxamine and ICI-118,551 with pA2 values of 6.86 and 8.73, respectively. The pA2 values of β-adrenoceptor antagonists (propranolol, bupranolol, atenolol, butoxamine and ICI-118,551) tested against adrenaline were consistent with the values when tested against salbutamol, a β2-selective adrenoceptor agonist. The present findings provide evidence that the relaxant response of the smooth muscle of the guinea-pig trachea to the adrenal medulla hormone, adrenaline, is mainly mediated through β2-adrenoceptors.
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  • Yutaka Okishio, Tadayoshi Takeuchi, Akikazu Fujita, Kiyotaka Suenaga, ...
    2005 Volume 41 Issue 3 Pages 163-174
    Published: 2005
    Released on J-STAGE: July 09, 2005
    JOURNAL FREE ACCESS
    Recently an essential role of interstitial cells of Cajal (ICC) within myenteric plexus (ICC-MY) was suggested in ascending contraction and descending relaxation in the mouse ileum. The role of ICC in these neural reflexes was examined in the distal colonic segments prepared from the wild type and c-kit mutant, W/WV mice, in the present study. Localized distension of the segments from the wild type mice by using a small balloon resulted in ascending contraction and descending relaxation. In the segments from the mutant mice, localized distension also induced these neural reflexes similar to those observed in the wild type mice. Immunohistochemical examination demonstrated that ICC-MY and ICC present in muscle layers (ICC-IM) were severely disrupted in the mutant mouse, but only ICC, present within submucosal plexus (ICC-SMP), remained unchanged. In the small strips with ICC-SMP absent prepared from the mutant mouse, electrical field stimulation induced contraction or relaxation in the absence or presence of atropine, respectively. It was suggested that ICC have no important role in the ascending and descending neural reflexes in the mouse distal colon, this is in direct contrast to the role of ICC-MY in the ileum.
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