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KMID : 0376219920290010009
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Chonnam Medical Journal
1992 Volume.29 No. 1 p.9 ~ p.20
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Central inhibition of chronotropic baroreflexes in urethane-anesthetized rabbits
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Abstract
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Effects of intracerebroventricular (icv) infusion of various agents on chronotropic baroreflexes induced by intravenous phenylephrine (PE) and sodium nitroprusside (SNP) were investigated in urethane-anesthetized rabbits.
SNP-induced depressor response response(SNP-depressor) was not affected by icv infusions of verapamil (6㎍/kg/min), nifedipine (6㎍/kg/min) and fluarizine(40㎍/kg/min), but SNP-induce dbaroreflex tachycardia (SNP-tachycardia) was markedly
inhibited
by
above three drugs. The three calcium antagonists significantly inhibited PE-induced pressor response (PE-pressor) land markedly attenuated PE-induced baroreflex bradycardia(PE-bradycardia). Intravenous infusion of the same doses of verapamil and
nifedipine inhibited both chronotropic baroreflexes induced by PE and SNP in accordance with decreasing fo blood pressure responses to both drugs.
Clonidine(4.5㎍/kg/min) potentiated PE-pressor but did not affect PE-bradycardia. SNP-depressor was not affected by the clonidine. While SNP-tachycardia was markedly inhibited by the clonidine. Though neither PE-pressor nor SNP-tachycardia were
significantly inhibited by the phenoxybenzamine. Atropine (3㎍/kg/min) did not affect blood pressor responses and chronotropic baroreflexes induced by both PE and SNP at all. While diazepam(40㎍/kg/min) did not inhibited either PE-pressor or
SNP-depressor, it significantly attenuated both PE-bradycardia and SNP-tachycardia.
Above results suggest that positive and negative chronotropic baroreflexes by changes of arterial prssure are dependent on calcium metabolism in central nervous system and GABA-ergic system is partly involved in the baroreflex regulation.
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KEYWORD
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