Abstracts of papers pharmacological meeting

s of papers CENTRAL HYPOTENSIVE ACTIVITY OF KETANSERIN IN CATS H.W.G.H. Boddeke, H.N. Doods and P.A. van Zwieten Ketanserin, a 5HT2and ~ -antagonist, elicits antihypertensiva activity in humans and in animal models. However, not all details of the mechanism underlying this antihypertensive effect are clearly understood. In the present study the possibility of a central hypotensive effect of ketanserid was investigated in chloralose-anaesthetized cats. Ketanserin (10-100 pg/kg/min), when infused into the left thoracic vertebral artery (l.v.a.) of chloralose-anaesthetized cats, induced a dose-dependent hypotensive effect, accompanied by a modest bradycardia, that was stronger than the effect of ketanserin (30-300 pg/kg/min) administered via the systemic circulation. The selective 5HT2-antagonist rltanserin did not lower blood pressure, when infused into the l.v.a., thus suggesting that central 5HT2-receptors do not play a significant role in the central hypotensive action of ketanserin. Similarly, pretreatment with corynanthine and rauwolscine, respectively, did not change the central hypotensive action of ketanserin, thus ruling out involvement of ~ or ~-adrenoceptors. However, the central hypotensive action could be blocked by atropine, when inJected into the l.v.a., but not by N-methylatropine, when administered systemically. It seems unlikely that ketanserin directly interacts with muscarinic receptors in the CNS, but an interaction of ketanserin with the baroreceptor reflex, thus indirectly modulating cholinergic receptors in the reflex arc~ may be an explanation for the influence of atropine on the central hypotensive effect. Division of Pharmacotherapy, University of Amsterdam, P l a n t a g e Huidergracht 2h, 1 0 1 8 TV Amsterdam, The