REGULATION OF GASTRIN-RELEASE IN THE DOG BY ALPHA(2)-ADRENOCEPTORS

1 The purpose of the present study was to analyse the effects of the a lpha(2)-adrenoceptor agonist medetomidine and the antagonist yohimbine on gastrin release in conscious dogs. 2 Gastrin secretion was investi gated under both basal conditions and stimulation by 2-deoxy-D-glucose , food or bombesin. 3 Basal gastrin under fasting conditions was signi ficantly reduced by medetomidine and increased by yohimbine. 4 2-deoxy -D-glucose-induced gastrin increase was fully inhibited by medetomidin e; this effect was antagonized by yohimbine. 5 Medetomidine significan tly inhibited food-induced increase in plasma gastrin; under these con ditions yohimbine was without effect per se, but significantly antagon ized the inhibitory action of medetomidine. 6 Gastrin release induced by bombesin was not affected by medetomidine or yohimbine. 7 These res ults suggest that alpha(2)-adrenoceptors play an inhibitory role under conditions in which gastrin release is mainly mediated through cholin ergic and non-cholinergic nervous pathways; in contrast, they do not i ndicate the presence of alpha(2)-adrenoceptors on G cells of the dog s tomach.