Role of cholinergic receptors in adrenal catecholamine secretion in spontaneously hypertensive rats

We investigated the role of nicotinic and muscarinic receptors in secretion of catecholamines induced by transmural electrical stimulation (ES) from i solated perfused adrenal glands of spontaneously hypertensive rats (SHRs) a nd normotensive Wistar-Kyoto (WKY) rats. ES (1-10 Hz) produced frequency-de pendent increases in epinephrine (Epi) and norepinephrine (NE) output as me asured in perfusate. The ES-induced increases in NE output, but not Epi out put, were significantly greater in adrenal glands of SHRs than in those of WKY rats. Hexamethonium (10-100 mu M) markedly inhibited the ES-induced inc reases in Epi and NE output from adrenal glands of SHRs and WKY rats. Atrop ine (0.3-3 mu M) inhibited the ES-induced increases in Epi and NE output fr om adrenal glands of SHRs, but not from those of WKY rats; These results su ggest that endogenous acetylcholine-induced secretion of adrenal catecholam ines is predominantly mediated by nicotinic receptors in SHRs and WKY rats and that the contribution of muscarinic receptors may be different between these two strains.