Fig. 3.

Voltage dependency of DPDPE action on HVA Ba²⁺ currents. A, Ba²⁺ currents recorded with the perforated patch-clamp method in a GLC8 cell bathed in 50 mmBa²⁺. The two traces in each panel were recorded before (C) and during application of 0.3 μm DPDPE (open circles) at the potential indicated. V_h −90 mV.Inset, I–V curves in 50 mm Ba²⁺ recorded using a depolarizing ramp of 1.2 mV/msec from −90 mV holding potential before and during exposure to 1 μm DPDPE.B, Facilitation of DPDPE-inhibited Ba²⁺ currents induced by conditioning prepulses in whole-cell clamp recordings. The two overlapping traces in each panel were recorded on test depolarizations to +30 mV without (trace a) and with (trace b) a 50 msec conditioning prepulse to +90 mV. The double-pulse protocol was delivered before (top) and during (bottom) application of DPDPE with 6 sec interval between pulses. Vertical arrows indicate the time of peak control current at which DPDPE inhibition is estimated during test pulses. Horizontal arrows indicate the current amplitude reached at the test potential (+30 mV) soon after the prepulse.