NEUROPEPTIDE-Y POTENTIATES CALCIUM-CHANNEL CURRENTS IN SINGLE VASCULAR SMOOTH-MUSCLE CELLS

The effect of neuropeptide Y (NPY) on Ca2+-channel currents in isolate d vascular smooth muscle cells was studied with the perforated-patch r ecording technique. Using Ba2+ (10 mM) as the charge carrier, inward c urrents sensitive to Cd2+ and nifedipine were potentiated by NPY in a concentration-dependent manner. The threshold concentration for the po tentiating effect of NPY was 50 nM and reached a maximum at 150 nM. NP Y shifted the steady-state activation curve to less positive membrane potentials by about 6 mV so that the potentiating effect was most prom inent near the activation threshold of the current. It had no effect o n steady-state inactivation of the current. These results suggest that NPY may potentiate vasoconstriction by promoting calcium entry throug h L-type voltage-dependent Ca2+-channels.