The effect of PKC activity on the TTX-R sodium currents from rat nodose ganglion neurons

To determine how protein kinase C (PKC) activity influences properties of the tetrodotoxin-resistant sodium current (TTX-R I(Na)) in neonatal rat nodose ganglion (NG) neurons, we assessed the effects of phorbol,-12-myristate,13-acetate (PMA), one of the PKC activators, and staurosporine, one of the PKC inhibitors, on the current. PMA (30 and 100 nM) induced an increase in the peak current amplitude of normalized current-voltage curves, a leftward shift in the potential for half activation (V(1/2)) of normalized conductance-voltage curves and a leftward shift of V(1/2) potential for steady-state inactivation curves. The effects of staurosporine (0.1 and 1 muM) on the peak current amplitude and the V(1/2) potential for activation were opposite compared with those seen after PMA application. Staurosporine (1 muM) antagonized PMA (100 nM)-induced modification of TTX-R I(Na). These results suggest that the basal TTX-R I(Na) obtained from neonatal NG neurons is controlled by the level of PKC activity.