Fig. 7.

Effects of SP (1 μm) in a low (27 mm)- or control (151 mm)-Na⁺ solution. NaCl was replaced by choline-Cl in the low-Na⁺ solution. Ramp voltage pulses (from −100 to 10 mV, 40 sec) were applied before and during the application of SP. TTX (0.3 m) was applied throughout the experiment. A, The SP-induced current was substantially decreased in the low-Na⁺solution. B, I–V curves before and during SP application obtained in the normal (a)- and low (b)-Na solutions. The SP-induced current (I_SP) curve was constructed by subtracting the I–V curve obtained before SP application from the curve obtained during the peptide application. Note the dramatic reduction of I_SP in a low-Na⁺ solution.