Inhibition of barium-induced constriction of cerebral surface arterioles by blockers of calcium channels

Barium ion, applied as BaCl2 to the cerebral surface, produces marked constriction of pial arterioles. The present data demonstrate that this constriction is inhibited by the calcium channel blockers verapamil and nimodipine. Verapamil in concentrations as low as 10)-7) M was effective in local administration. Verapamil in milligram per kilogram doses and nimodipine in microgram per kilogram doses were effective 30 min after intraperitoneal injection without producing dilation. The basis for the inhibitory action of the calcium channel blockers is not established by the data. However, in view of barium's known ability to depolarize membranes, it may be that the constriction which results is related to inward passage of ions and is facilitated by inward movements of calcium.