Calcium, calcium blockers, and nasal smooth muscle.

A canine in vitro nasal blood vessel preparation was tested to determine the effects of calcium (Ca) on smooth-muscle contraction. The contractions induced by either electrical stimulation or vasoconstricting agents were reduced or abolished by reducing the concentration of the Ca in the medium. The Ca response was dose-dependent and reversed at a high concentration. Contractions induced by vasoconstrictors were more resistant to the change of the Ca concentration than by electrical stimulation. Verapamil, a blocker of Ca entry, inhibited the contraction by simulating Ca depletion. These changes show that the extent of Ca influx regulates the smooth-muscle contraction of the nasal blood vessels consistent with the reports concerning other vascular smooth muscle.