Figure 2.

Depolarization-induced disinhibition of I_pCa. I_pCa was evoked by a depolarizing test pulse from a holding potential of −80 mV to different membrane potentials by 10-mV steps with (□) or without (○) a prior conditioning depolarizing pulse (to +100 mV, duration 10 ms). (Left) Experimental paradigm (Top) and sample records of I_pCa evoked by depolarizing steps to −10 mV. Calibrations are 5 ms and 0.5 nA. (Right) In the current–voltage relationship, the I_pCa amplitude was normalized to that at −10 mV without conditioning. Recording pipettes contained Gβγ (A) or boiled Gβγ (B) (200 nM each), or none of them (C). In C, baclofen (20 μM) was present in superfusates. Mean amplitudes and SEM were derived from 6 (A), 8 (B), and 4 (C) calyces, respectively. Asterisks indicate data points of significant difference (P < 0.02).