Effects of calcium channel blockers on pial vascular responses to receptor mediated constrictors

Published studies have seldom examined the in vivo effect of calcium channel blockers on the contractile response of cerebral vessels to receptor mediated constrictors, and have had little success in demonstrating any effect of a single systemic dose of the channel blockers in contrast to the effects of continuous infusions. The present study examines the effect of topical norepinephrine, prostaglandin F2 alpha and serotonin on pial arterioles of the mouse, in the presence of locally applied channel blockers and also 15 and 30 minutes after a single i.p. injection of the blockers. Verapamil, nisoldipine and nimodipine were all effective inhibitors of constriction by either route of administration, and in doses having little or no dilating action. The data not only indicate that single systemic doses can effectively alter contractile behavior of cerebral arterioles, but also demonstrate the importance of testing these drugs against receptor mediated constrictors whose effects, alone or in combination, may be important during initiation or maintenance of cerebral vasospasm.