Interactions between guanabenz and clonidine in their cardiovascular effects in the rat

In Sprague-Dawley rats anesthetized with pentobarbital sodium (40 mg/kg, i.p.), guanabenz and clonidine exhibited mutually interactive effects on the cardiovascular system. Pretreatment with either antihypertensive agent (5 or 10 μg/kg, i.v.) significantly potentiated both the degree and duration of the initial elevation in arterial pressure and cardiac contractility promoted by the other compound (10 μg/kg, i.v.). On the other hand, discernible antagonization existed mutually for their delayed hypotensive, as well as negative inotropic and chronotropic actions. Furthermore, these circulatory changes displayed comparable trends under parallel drug interaction schemes, as revealed by correlation coefficient evaluations. It is possible that guanabenz and clonidine may share a common mechanism(s) in their cardiovascular actions.