Effects of α-conotoxin c-Vc1.1 and baclofen (bac) on stably expressed human Ca_v2.1 (α_1A-2) or human Ca_v2.3c (α_1E-c) channels in the presence of transiently expressed human GABA_BR subunits R1 and R2 (GABA_BR). (A and B) 50 µM baclofen inhibits Ca_v2.1 or Ca_v2.3c channel currents, whereas 200 nM c-Vc1.1 only inhibits Ca_v2.3c currents. Bars indicate c-Vc1.1 or baclofen application. I_Ba was evoked by 150-ms depolarizations to 10 mV (Ca_v2.3c) or 15 mV (Ca_v2.1), applied every 10 s from an HP of −80 mV (voltage inset). Peak current amplitudes were plotted as a function of time. Representative I_Ba traces (right) are shown at the times indicated by lowercase letters. Horizontal dotted line represents zero-current level. Note that Ca_v2.1 current inhibition by baclofen is reversible on washout (A), whereas baclofen or c-Vc1.1 irreversibly inhibits Ca_v2.3c currents (B). (C) 50 µM baclofen inhibits I_Ba in Ca_v2.3/GABA_BR cells. Experimental procedures are similar to those in A or B.