Fig. 4.

Substrate-induced current in HP-21 cells. Shown is substrate-induced current after bath application of PRO to a voltage-clamped HP-21 cell. The holding potential was −40 mV, and the test potential was −140 mV for 500 msec. After 40 μm PRO was added to the bath, the inward current increased at −40 and −140 mV. Substrate-induced current is defined as the difference between the background current (Cont) and PRO-induced inward current. The traces represent raw data without leak subtraction or capacity compensation. The inset shows the inward current induced by bath application of PIP (40 μm) at −120 mV. External GGFL was 100 μmand was added in the presence of PRO or PIP.