Effects of buflomedil on isolated dog arteries.

Buflomedil (10(-6) to 10(-4) M) relaxed, in a concentration-dependent manner, helical strips of dog mesenteric, renal and femoral arteries, partially contracted due to previous exposure to noradrenaline. When partial contraction was caused by prostaglandin F2 alpha, Buflomedil produced a slight relaxation of the mesenteric and coronary arterial strips, had no effect in cerebral and femoral arteries and caused a small contraction of renal arterial strips. Buflomedil did not reduce contractions induced by submaximal concentrations of K+ in normal media and those induced by Ca++ in mesenteric arteries exposed to Ca++-free media and depolarized by excess K+. Contractile responses to transmural electrical stimulation and exogenous noradrenaline were attenuated by buflomedil; the attenuations in femoral and mesenteric arteries did not differ. Protection against persistent blockade of alpha-adrenoceptors by phenoxybenzamine was obtained by pretreatment of mesenteric arteries with buflomedil. Relaxant responses of cerebral and coronary arteries to nicotine were suppressed or abolished by buflomedil, whereas the relaxation of coronary arteries induced by tyramine was unaffected or reduced only slightly. It is concluded that buflomedil reversibly blocks alpha-adrenoceptors in arterial smooth muscle and possesses an anti-nicotinic action. As far as the concentrations used in the present study are concerned, buflomedil does not appear to interfere with the transmembrane influx of Ca++.