Calcium influx and spontaneous phasic contractions of portal veins after treatment with reserpine, 6-hydroxydopamine, and cocaine.

Reserpine treatment increased the amplitude of the spontaneous phasic contraction (SPC) of portal veins obtained from rabbit and guinea pig but did not alter that of rat. The amplitude of the SPC of portal veins from these animals was increased after 6-hydroxydopamine (6-OHDA) but was not changed after cocaine treatment. Reserpine- and 6-OHDA-induced changes in portal vein SPC amplitude were accompanied by an increase in 45Ca influx. These results indicate that the elevation in SPC amplitude is accompanied by an increase in calcium influx.