Arteriolar and venular vasodilating properties of benidipine hydrochloride, a 1,4-dihydropyridine Ca2+ antagonist with long-lasting action, assessed in rat mesenteric microcirculation

To obtain direct and visible evidence of the arteriolar vasodilating action in vivo of benidipine hydrochloride, a long-lasting and light-resistant Ca 2+ antagonist of the 1,4-dihydropyridine type, we continuously recorded cha nges in the diameter of mesenteric arterioles (10-40 mu m) and venules (20- 40 mu m) in anesthetized agent-injected Wistar rats by means of digital ima ge processing combined with videomicroscopy. Benidipine injected intravenou sly brought about a depressor response, and this response persisted much lo nger than that induced by nifedipine. Benidipine produced a dose-dependent arteriolar vasodilation and a decrease in the bloodflow velocity. It also r elaxed the venules during the depressor response, which relaxation was more prominent 1-2 h after the administration. In pithed rats, both presser res ponse and arteriolar constriction induced by norepinephrine were prevented by benidipine. Benidipine also inhibited adenosine diphosphate (ADP)-induce d interruption of arteriolar blood flow. These results suggest that benidip ine produced vasodilation in vivo at both the arteriolar and venular levels . The ability of benidipine to prevent microcirculatory disturbance and to produce arteriolar and venular vasodilation seem to account for its long-la sting Ca2+-antagonistic antihypertensive action.