Absence of nicotinic receptors mediating the release of norepinephrine from adrenergic neurons in the rat heart.

Abstract

Introduction. It appears well established that cholinergic receptors of the nicotinic type exist on some adrenergic nerve terminals (1-6), and that activation of these receptors results in a release of NE (4-8). Numerous drugs appear to have the ability to antagonize these responses (4, 5, 8). The physiological significance of these receptors remains obscure, although they have been postulated to mediate the cholinergic link in adrenergic transmission as proposed by Burn and Rand (9). The receptors are of great pharmacological interest since nicotine is the major ingredient in tobacco (10). In the course of experiments carried out to gain a better understanding of the action of nicotine on the release of NE from adrenergic nerve terminals experiments were carried out on the isolated perfused rat heart. The present studies demonstrate that unlike the rabbit, cat, dog, and guinea pig heart, nicotine does not induce a release of NE from the rat heart (5-8, 11, 12).Methods. Male Sprague-Dawley rats weighing b...