Cerebral arterial spasm: part 9. In vitro effects of nifedipine on serotonin-, phenylephrine-, and potassium-induced contractions of canine basilar and femoral arteries.

We performed in vitro experiments with a small volume chamber to determine the inhibitory effect of nifedipine on serotonin-, phenylephrine-, and potassium-induced contractions of canine basilar and femoral arteries. Nifedipine, an inhibitor of the influx of extracellular calcium into smooth muscle cells, was found to be a sensitive inhibitor of contractions of the basilar artery induced by all three agents. In contrast, nifedipine did not significantly inhibit the serotonin- and phenylephrine-induced contractions of the femoral artery but did inhibit potassium-induced contractions of the femoral artery. Calcium-induced contractions of the basilar artery were also inhibited by nifedipine. These experiments demonstrate a relatively selective effect of nifedipine on the basilar artery, and a mechanism to explain this selective effect is postulated.