Voltage-clamp evidence for differential expression of a BK-type KCa current. A: from a cell classified as an unmyelinated C-type VGN, depolarizing voltage-clamp steps revealed a large, sustained outward K+ current (IK,total). B: K+ current eliminated with the application of 100 nM ChTX (subtracted records, see text). For A and B, the activation protocol consisted of 300-ms voltage-clamp steps at 3-s intervals from a Vhold of −80 mV to +40 mV in increments of +10 mV. C: normalized current-voltage (I-V) relationship for the whole cell K+ currents from cells classified as unmyelinated C-type VGN under control (CNTRL, n = 8) conditions and in the presence of 100 nM ChTX. D: normalized I-V relationship for the whole cell K+ current from cells classified as a myelinated A-type VGN under control (CNTRL, n = 7) conditions and in the presence of 100 nM ChTX. For C and D, data are means ± SD of measures made 250 ms into the clamp step (dotted trace, Fig. 7A) with *P < 0.05 and **P < 0.01 vs. CNTRL.