Figure 8.

TTX-S and TTX-R sodium currents flowing during the voltage waveform elicited by capsaicin application. Top, Voltage command taken from current-clamp response to 500 nm capsaicin (Fig. 1 A). Middle, TTX-R sodium currents flowing in response to capsaicin response waveform. To improve voltage control, currents were recorded in an external solution with reduced sodium containing the following (in mm): 50 NaCl, 100 TEA-Cl, 4 CsCl, 2 CaCl₂, 2 MgCl₂, 0.03 CdCl₂, 10 glucose, and 10 HEPES, pH 7.4 (with TEA-OH). Outward currents occur when spike height exceeds sodium reversal potential in reduced sodium (∼31 mV). Bottom, TTX-S sodium current flowing during the capsaicin response waveform, determined as the current sensitive to block by 300 nm TTX in an external solution containing the following (in mm): 50 NaCl, 100 TEA-Cl, 2 BaCl₂, 0.3 CdCl₂, 10 glucose, and 10 HEPES, pH 7.4 (with TEA-OH) (different cell from top). The internal solution for both recordings contained the following (in mm): 126 NMDG, 120 aspartate, 15 NaCl, 1.8 MgCl₂, 9 EGTA, and 9 HEPES, pH 7.4 (with 7 mm CsOH).