Effect of chronic treatment with hydralazine on various in vitro preparations of rat

Effect of chronic treatment with hydralazine (40 mg/kg/day) on isolated heart, anococcygeus muscle and myometrial preparations from rats has been studied. The treatment for 6 weeks caused a significant increase in isoprenaline induced positive inotropic response in rat heart. However, isoprenaline induced positive chronotropic effects were not altered significantly by chronic hydralazine treatment. Chronic hydralazine treatment also failed to alter noradrenaline induced contractile effects on rat anococcygeus muscle. However, on myometrial preparations from hydralazine treated rats showed an increase in adrenaline induced relaxations. The results of the present study can be explained on the basis of the effect of hydralazine on adenylate cyclase-cyclic adenosine monophosphate (cAMP).