AGE-DEPENDENCE OF THE CHRONOTROPIC RESPONSE TO NORADRENALINE, ACETYLCHOLINE AND TRANSMURAL STIMULATION IN ISOLATED RABBIT ATRIA

Japanese journal of pharmacology Pub Date : 1976-01-01 DOI:10.1254/jjp.26.359

Noboru TODA , Wang L.H. FU , Yoshitsugu OSUMI

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引用次数: 10

Abstract

The chronotropic response to noradrenaline, tyramine, acetylcholine and transmural electrical stimulation was compared in atria isolated from rabbits at different stages of development after birth (day 2 to day 210). Pacemaker rates under steady state conditions were related inversely to days after birth; the rate in atria from rabbits at day 2 was significantly greater than that at days 10-210. The rate of neonatal rabbit atria was not significantly reduced by propranolol and the positive chronotropic response to noradrenaline was not significantly different in atria from different ages of rabbits as far as threshold concentrations for inducing tachycardia and ED50’s were concerned. The maximum rate induced by noradrenaline was higher in neonatal rabbit atria than in adult rabbit atria. The effect of tyramine was approx. the same regardless of age. Increase in the pacemaker rate induced by transmural neural stimulation varied directly with age. The negative chronotropic effect of acetylcholine was greater in neonatal than in adult rabbit atria; the ED50 in the former was significantly less than in the latter. Bradycardia induced by transmural stimulation of intracardiac cholinergic nerves was related directly to age. Tachycardia in the neonatal rabbit atria may be due to electrogenic characteristics of pacemaker cells which differ from those in adult rabbit atria. Our evidence strongly suggests that the adrenergic and cholinergic nerves innervating the S-A node develop at an early postnatal stage in the rabbit.

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离体兔心房对去甲肾上腺素、乙酰胆碱和跨壁刺激的变时反应的年龄依赖性

摘要比较了兔出生后不同发育阶段(第2 ~ 210天)离体心房对去甲肾上腺素、酪胺、乙酰胆碱和跨壁电刺激的变时性反应。稳定状态下起搏器频率与出生后天数成反比;第2天家兔心房内的比例显著高于第10-210天。就诱发心动过速的阈值浓度和ED50而言，不同年龄兔心房对去甲肾上腺素的正性变时反应无显著差异。去甲肾上腺素对新生兔心房的最大诱导率高于成年兔心房。酪胺的作用近似。无论年龄大小都一样。经壁神经刺激引起的起搏器率升高与年龄直接相关。乙酰胆碱在新生兔心房的负性变时作用大于成年兔心房;前者的ED50显著低于后者。经壁胆碱能神经刺激引起的心动过缓与年龄直接相关。新生儿兔心房心动过速可能是由于起搏器细胞的电致特性不同于成年兔心房。我们的证据强烈表明，支配S-A结的肾上腺素能和胆碱能神经在家兔出生后早期发育。

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Japanese journal of pharmacology

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