The intracerebroventricularly (i.c.v.) injected presynaptic α2-adrenoceptor agonists, clonidine and oxymetazoline, exerted a dose-dependent inhibition on the gastric acid secretion in pylorus-ligated rats; the ED50 values were 20 and 7.5 nmol/rat, respectively. Moreover, β-endorphin, given i.c.v., also decreased acid secretion (ED50 = 0.25 nmol/rat i.c.v.). The antisecretory effect of these compounds was highly reduced by glibenclamide (10 nmol/rat i.c.v.), a selective blocker of KATP channels. These results suggest that KATP channels in the central nervous system are likely to be involved in the centrally initiated antisecretory action of both α2-adrenoceptor agonists and β-endorphin.
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