[Effect of an antihypertensive drug, budralazine, on the cerebral circulation in spontaneously hypertensive rats].

Budralazine was evaluated for its effect on the cerebral blood flow (CBF) in comparison with some antihypertensive drugs in spontaneously hypertensive rats (SHR). The oral doses for each drug were selected to reduce arterial blood pressure to near normotensive levels. Equihypotensive rats were also produced by a controlled-hemorrhage and used as a control group. The blood flows in the parietal cortex and caudate nucleus were measured using the hydrogen clearance method at the time points when the pressure levels averaged about 120 mmHg after administration of each of the drugs or controlled-hemorrhage. Budralazine (40 mg/kg) significantly increased the regional CBF by approximately 60% with a significant decrease in the cerebral vascular resistance. A similar effect was also observed with hydralazine (9 mg/kg). The CBF-increasing effect of nifedipine (7 mg/kg) was less potent than that of budralazine. Neither prazosin (6 mg/kg) nor alpha-methyldopa (1,000 mg/kg) increased the regional CBF. Such cerebrovascular responses were also observed with controlled-hemorrhage. Furthermore, budralazine given intravenously (3-10 mg/kg) caused a significant and dose-dependent increase (50-250%) in the regional CBF without affecting the arterial blood pressure. This effect of budralazine was partially attenuated by the pretreatment with either reserpine or 6-hydroxydopamine. It is possible that catecholaminergic control of cerebrovascular tone is at least in part involved in the mechanism whereby budralazine increases the CBF.