SDZ NVI 085, an alpha 1A-adrenoceptor agonist with 5-HT2A receptor antagonist properties

(+/-)-SDZ NVI 085 (3,4,4a,5,10,10a-hexahydro-6-methoxy-4-methyl-9- methylthio-2H-naphth [2,3-b]-1,4-oxazine hydrochloride), an alpha 1-adrenoceptor agonist, produced a concentration-dependent relaxation (pIC50 of 7.2 +/- 0.1) in the isolated caudal artery of rat precontracted with serotonin (5-hydroxytryptamine, 5-HT, 1 microM). (+/-)- SDZ NVI 085 had no effect upon caudal arteries precontracted with vasopressin or U46619 (9,11-dideoxy-11 alpha, 9 alpha-epoxymethano-prostaglandin F2 alpha). In other studies, (+/-)-SDZ NVI 085 shifted 5-HT concentration-effect curves to the right, in a concentration-dependent manner, and Schild regression gave a pA2 estimate of 8.0 (slope of 1.0). Experiments using pharmacological resultant analysis indicated a syntopic interaction of (+/-)-SDZ NVI 085 with ketanserin (a 5-HT2 receptor antagonist) toward 5-HT-induced contractions. It is concluded that (+/-)-SDZ NVI 085 behaves as a reversible competitive 5-HT2A receptor antagonist, a property which may be of importance regarding its pharmacological effects in vivo.