The effects of an intravenous injection of the novel calcium channel blocker, nilvadipine, on the relative regional cerebral blood flow and relative regional skin blood flow were studied in anesthetized cats using the laser-Doppler method. The effects of nilvadipine were compared with those of nicardipine hydrochloride (nicardipine). Nilvadipine and nicardipine both increased the relative regional cerebral blood flow dose-dependently, in spite of their hypotensive effect. At a dose of 32 micrograms/kg, nilvadipine and nicardipine increased the relative regional cerebral blood flow by 61 +/- 8% and 25 +/- 10% of the predrug value, respectively, 15 min after administration. At this time, both drugs induced a comparable degree of hypotension: -18 +/- 3% of the predrug value for nilvadipine and -25 +/- 2% for nicardipine. After nilvadipine, the relative regional cerebral blood flow enhanced by 45 +/- 10% 180 min after drug administration, whereas after nicardipine, it returned to the predrug value within 60 min. In contrast, the increase in relative regional skin blood flow produced by nilvadipine (32 micrograms/kg) and nicardipine (32 micrograms/kg) was 23 +/- 15% and 32 +/- 8% of the predrug value, respectively, 5 min after drug administration. The effect of nicardipine on the relative regional skin blood flow, compared with that of control, was significantly higher. These results indicate that nilvadipine exhibits a pronounced and longer-lasting effect on the relative regional cerebral blood flow, compared with the relative regional skin blood flow, and that its action on the relative regional cerebral blood flow is more potent than that of nicardipine.