Neurokinin mediated increase in firing is not reversed by inhibition of PKC or mimicked by direct activation of PKC with phorbol ester. A, In a phasic firing neuron SP (0.5 μM, middle trace) increased firing from 1 AP (top trace, control) to 5 APs. Application of a PKC inhibitor, bisindolylmaleimide I HCl (BIM, 0.5μM, bottom trace), partially reduced the increase in firing to 3APs. Firing in response to a current injection 600 ms long and 250 pA in intensity. B, Average increase in APs in response to SP and BIM after SP in 5 neurons. C, Direct activation of PKC with phorbol 12,13-dibutyrate (PDBu, 0.5 μM, bottom trace) did not alter significantly (top trace, control) firing. Firing in response to a current injection 600 ms long and 250 pA in intensity. D, Average firing before and after PDBu in 5 neurons. E, Dependence of firing on stimulus intensity for experiment in D, before (Control, empty circles) and after PDBu (0.5 μM, filled circles).