CHARACTERIZATION OF ALPHA(2)-ADRENOCEPTOR SUBTYPES INVOLVED IN THE MODULATION OF GASTRIC-ACID SECRETION

The effects of several alpha(2)-adrenoceptor agonists and antagonists were examined on gastric acid secretion from reserpinized rats undergo ing electrical stimulation of the left vagus nerve. Both detomidine an d oxymetazoline inhibited vagal acid hypersecretion, their effects bei ng fully prevented by idazoxan, 7,8-(methylenedioxy)-14-alpha-hydroxya lloberbane (CH 38083), or 2-(2-methoxy-1,4-benzodioxan-2-yl)2-imidazol ine (RX 821002), and partly antagonized by yohimbine or rauwolscine. l )-ethyl-4,4-dimethyl-1,3-(2H,4H)-isoquinolindione (ARC 239) did not af fect the antisecretory action of the two agonists, while prazosin at t he highest dose was partly effective only against detomidine. Atropine markedly reduced vagally evoked acid output. It is suggested that aci d secretion induced by vagal cholinergic stimulation is modulated by a lpha(2A)-like adrenoceptor subtypes.