AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 1 44-R50, Copyright © 1990 by American Physiological Society

ARTICLES

Sympathetic modulation of cholinergic transmission in cat vesical ganglia is mediated by alpha 1- and alpha 2-adrenoceptors

J. R. Keast, M. Kawatani and W. C. De Groat
Department of Pharmacology, School of Medicine, University of Pittsburgh, Pennsylvania 15261.

Modulation of transmission in cat vesical ganglia by exogenous catecholamines or short periods of hypogastric nerve stimulation (HGS) was examined in vivo. HGS (30 Hz, 30 V, 10- to 20-s train) initially caused inhibition of ganglionic transmission, followed by a period of facilitation. The inhibition could be evoked by lower stimulus intensities than the facilitation. The biphasic effect was mimicked by norepinephrine (2-10 micrograms) injected into the inferior mesenteric artery, whereas phenylephrine (5-10 micrograms) usually caused only facilitation. The administration of specific adrenoceptor antagonists showed that the inhibitory responses were mediated by alpha 2-receptors and the facilitatory responses by alpha 1-receptors. The effects of HGS and norepinephrine were also tested on pelvic nerve-evoked bladder contractions. Both caused a brief reduction in contraction amplitude which, for the HGS effect, was mediated mainly by alpha 2-receptors. Noradrenergic inhibition of bladder contractions was mediated by both alpha 2- and beta-adrenoceptors. These studies have shown that sympathetic modulation of ganglionic transmission in the bladder can be either inhibitory or facilitatory, each mediated by a specific receptor type. These two actions may be important during different stages of bladder storage or voiding.

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