KMID : 0811720070110030097
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Korean Journal of Physiology & Pharmacology 2007 Volume.11 No. 3 p.97 ~ p.106
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Influence of Nicorandil on Catecholamine Release in the Perfused Rat Adrenal Medulla
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Koh Young-Youp
Lim Dong-Yoon Lee Eun-Sook No Hae-Jeong Woo Seong-Chang Jeong Joong-Wha Seoh Yoo-Seung
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Abstract
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The present study was attempted to investigate the effect of nicorandil, which is an ATP-sensitive potassium (KATP) channel opener, on secretion of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused rat adrenal glands. The perfusion of nicorandil (0.3¡3.0 mM) into an adrenal vein for 90 min produced relatively dose-and time-dependent inhibition in CA secretion evoked by ACh (5.32 mM), high K+ (a direct membrane depolarizer, 56 mM), DMPP (a selective neuronal nicotinic receptor agonist, 100¥ìM for 2 min), McN-A-343 (a selective muscarinic M1 receptor agonist, 100¥ìM for 4 min), Bay-K-8644 (an activator of L-type dihydropyridine Ca2+ channels, 10¥ìM for 4 min) and cyclopiazonic acid (an activator of cytoplasmic Ca2+-ATPase, 10¥ìM for 4 min). In adrenal glands simultaneously preloaded with nicorandil (1.0 mM) and glibenclamide (a nonspecific KATP-channel blocker, 1.0 mM), the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were recovered to the considerable extent of the control release in comparison with that of nicorandil-treatment only. Taken together, the present study demonstrates that nicorandil inhibits the adrenal CA secretion in response to stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as by membrane depolarization from the isolated perfused rat adrenal glands. It seems that this inhibitory effect of nicorandil may be mediated by inhibiting both Ca2+ influx and the Ca2+ release from intracellular store through activation of KATP channels in the rat adrenomedullary chromaffin cells. These results suggest that nicorandil-sensitive KATP channels may play an inhibitory role in the regulation of the rat adrenomedullary CA secretion.
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KEYWORD
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Nicorandil, Glibenclamide, Catecholamine release, Adrenal medulla, ATP-sensitive K+ (KATP) channels
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