Fig. 7.

ω-CTx–GVIA removes a large proportion of DPDPE inhibition in nifedipine-treated cells. A, Comparison of 0.3 μm DPDPE action before (1) and after (2) two acute applications of 3 μmω-CTx in 2 mm Ca²⁺. On the left diagram, the dots represent peak Ba²⁺ currents recorded at +30 mV every 12 sec from V_h −90 mV. All bath solutions contained 3 μm nifedipine. Lower bars mark the time of toxin application (shadowed bars) and the interval in which DPDPE action was tested (filled bars). Upper bars indicate the Ba²⁺ and Ca²⁺concentrations of external solutions (in mm). On the right are the current traces recorded at the times (a–c) and intervals (1, 2) labeled on the left. ΔI_b and ΔI_a indicate the amount of DPDPE inhibition before and after the two toxin applications. B, Same as in A, but from a cell containing a higher density of N-type channels as proven by the potent block of Ba²⁺ currents by ω-CTx (tracesc, d). The strong inhibitory effect of DPDPE before toxin application (traces a–c) is partially preserved on residual ω-CTx-resistant currents.