RELAXANT EFFECTS OF MEFLOQUINE ON VASCULAR SMOOTH-MUSCLE IN-VITRO

We have studied the effects of mefloquine on isolated rat aorta. Meflo quine (10(-8)to 1.6 x 10(-4) mol . l-1) relaxed aortic rings precontra cted with both noradrenaline (10(-7) mol.l-1) and potassium chloride ( 60 mmol.l-1). The mefloquine-induced relaxation was somewhat attenuate d by removal of the endothelium.Contractile responses to noradrenaline , potassium chloride, and calcium chloride were reduced by incubating the aortic rings in physiological salt solution containing mefloquine, suggesting that mefloquine reduces calcium influx, which is required for excitation-contraction coupling. The results show that mefloquine relaxes vascular smooth muscle via mechanisms which are partly endothe lium-dependent and which is also associated with inhibition of Ca2+ in flux from the extracellular medium.