ALPHA(1D)-ADRENOCEPTOR AND ALPHA(1A)-ADRENOCEPTOR MEDIATE CONTRACTIONIN RAT RENAL-ARTERY

To investigate the alpha(1)-adrenoceptor subtype(s) mediating contract ion in rat renal artery, we have compared the effect of the alpha(1)-a drenoceptor antagonists, 5-methylurapidil, BMY 7378 (8-(2-(4-(2-methox yphenyl)-1-piperazinyl)ethyl) 8-azaspiro (4.5) decane-7,9-dione 2HCl) and chloroethylclonidine on functional responses to noradrenaline. A c lear blockade by chloroethylclonidine (10(-4) M) of noradrenaline-indu ced contraction was observed and, along with this effect, pK(B) values of 9.12 and 8.40 for BMY 7378 and 9.75 and 10.06 for 5-methylurapidil were obtained, indicating that the renal artery expresses the alpha(1 D)-adrenoceptor subtype as the one involved in contraction and not onl y the a, subtype as has been reported. (C) 1997 Elsevier Science B.V.