An analysis of blood pressure effects of nipradilol and prizidilol in normotensive and spontaneously hypertensive rats.

Nipradilol and prizidilol are beta-adrenoceptor blocking drugs with vasodilator action. These drugs lowered blood pressure (BP) in spontaneously hypertensive (SHR) rats acutely (24 hr) and subacutely (3 weeks) at doses of 10 and 20 mg/kg per day, p.o., respectively. Nipradilol decreased plasma renin concentration in acute and subacute studies, whereas it was unchanged with prizidilol treatment. Paradoxical effects of these drugs on BP were analyzed further: BP determined indirectly at the tail was slightly higher in SHR rats than the control, whereas BP determined directly through an aortic cannula without anesthesia, restraint, or prewarming was lower. We found that the discrepancy between BP values determined directly and indirectly was due to the increase in BP by prewarming stress during the determination by the tail cuff method.