Effect of substance P and a phorbol ester on K+ currents in CR tonic neurons. Effects of substance P (SP, A–B) and phorbol 12, 13-dibutyrate (PDBu, C–D) in CR tonic DRG neurons. A, C. Averages of peak amplitudes of inactivating K+ currents in control (con) conditions before drugs and after SP (0.5 µM, A, n = 6) and PDBu (0.5 µM, E, n = 4). B, D, Averages of peak amplitudes of non-inactivating currents in control (con) and a SP (B) or PDBu (D) in the same experiments as in A and C. Stimulus protocols were the same as described in Fig. 3. Statistical difference using a two tailed t-test, unequal variance difference: * P<0.05, ** P<0.01; ns, not significant.