The effects of B‐HT 920 and St 91 on venous haemodynamics in cats

Abstract— The present study reports the effects of 2‐amino‐6‐allyl‐5,6,7,8‐tetrahydro‐4H‐thiazolo‐[4,5‐d]azepin dihydrochloride (B‐HT 920) and 2‐(2,6‐diethylphenylimino)‐2‐imidazolidine hydrochloride (St 91) in autoperfused cat hindquarters since we have previously shown that clonidine lowered blood pressure, heart rate and vena cava blood flow (VCBF) but not hindquarters perfusion pressure, indicating a selective venodilator action of this drug (Bentley et al 1986). It was found that intravenous (i.v.) and intracisternal (i.c.m.) administration of B‐HT 920 caused essentially identical effects to those of Clonidine. St 91, given i.c.m. lowered blood pressure and VCBF but not perfusion pressure, while i.v. St 91 had little effect on these variables. Thus, parallel changes in blood pressure and VCBF occurred using both drugs, suggesting that these centrally‐acting clonidine‐like drugs also caused selective venodilatation. 1989 Royal Pharmaceutical Society of Great Britain