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Volume 107 (1996)
- Issue 6 Pages 259-
- Issue 5 Pages 213-
- Issue 4 Pages 173-
- Issue 3 Pages 97-
- Issue 2 Pages 47-
- Issue 1 Pages 1-
Volume 107, Issue 6
Displaying 1-3 of 3 articles from this issue
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Koki SHIGENOBU, Hikaru TANAKA, Hiroyasu SATOH1996 Volume 107 Issue 6 Pages 259-272
Published: 1996
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe pacemaker current (If) in embryonic chick ventricular myocytes is present, but decreases during development. β-Adrenergic agonists stimulate If, whereas muscarinic cholinergic agonists inhibit If and reverse β-adrenoceptor stimulation. G-proteins directly and indirectly couple autonomic receptors to If channels in embryonic ventricular cells. The If may contribute partly to the electrogenesis of the pacemaker potential. On the other hand, Ito current, voltage-dependent and 4-AP-sensitive, exists even in young embryonic cardiomyocytes, but not in all cells. The Ito increases during development, resulting in modulation of the action potential configuration. The action potential duration of guinea pig ventricular myocardium decreases during the late fetal period and increases postnatally. Single cell voltage clamp analyses revealed that the decrease and increase in action potential duration are due to developmental increases in the current densities of the calcium current and delayed rectifier potassium current, respectively. The role of the sarcoplasmic reticulum in contraction and relaxation of the guinea pig myocardium increases during fetal development.View full abstractDownload PDF (9423K) -
Yojiro UKAI, Takashi OGASAWARA, Yoshiaki YOSHIKUNI, Kiyoshi KIMURA1996 Volume 107 Issue 6 Pages 273-284
Published: 1996
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSCentral effects of montirelin hydrate (NS-3) were electroencephalographically investigated in cats with experimentally induced disturbance of consciousness. All experiments were conducted under the gallamine-immobilized and artificially ventilated acute experimental condition. NS-3 and TRH produced EEG activation in cats with lesions in the midbrain reticular formation in a dose-dependent manner. Similar effects were observed in cats with bilateral lesions of the posterior hypothalamic area. These effects of NS-3 were 30 to 100 times more potent than those of TRH. NS-3 at doses higher than 0.003 mg/kg restored the suppressed EEG dose-dependently in cats with cerebral ischemia produced by clamping the bilateral common carotid arteries and basilar artery. TRH showed no effect at a dose of 10 mg/kg. These results indicate that NS-3 might be an effective drug for treating the disturbance of consciousness.View full abstractDownload PDF (9152K) -
Matsuko MORIYASU, Masahiro NASU, Hideo HONDA, Tamami SAKAMOTO, Michio ...1996 Volume 107 Issue 6 Pages 285-297
Published: 1996
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe stimulatory effect of TA-0910 on the secretions of thyroid-stimulating hormone (TSH) and thyroid hormones was investigated in male and female rats. Single intravenous administration of TA-0910 at 8.3 nmol/body acutely elevated the plasma TSH level, with delayed and moderate increases of T3 and T4 in plasma. Similar increments of plasma TSH and thyroid hormones were observed when TRH was injected at the dose of 0.83 nmol/body. Oral administration of TA-0910 at 2.75μmo1/body was equally potent or slightly more potent to secrete TSH than TRH at 0.275 μimol/body. The elevated TSH by TA-0910 decreased to the control level within 2 hr after intravenous injection or within 6 hr after oral administration; on the other hand, the higher levels of the thyroid hormones were retained for up to 4 and 6 hr after intravenous and oral administration, respectively. These findings indicate that TA-0910 and TRH stimulate the secretion of TSH and thyroid hormones by a similar manner and that the TSH-secreting activity of TA-0910 is lower by an order of magnitude compared with that of TRH.View full abstractDownload PDF (9927K)
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