Effects of intracellular injections of phorbol ester and protein kinase C on cat spinal motoneurons in vivo.

In cat spinal motoneurons intracellular iontophoresis of phorbol 12, 13-diacetate or protein kinase C increases the afterhyperpolarization, the maximum rate of spike rise and the spike peak amplitude, without evident change in resting potential, input resistance and monosynaptic excitatory postsynaptic potential. Phorbol ester also reduces the accommodation of repetitive discharge evoked by intracellular current pulses. These data suggest that activation of protein kinase C facilitates the Ca2+-activated K+ current that mediates the afterhyperpolarization, as well as the fast Na+ current. These effects are quite different from those seen in some other mammalian central neurons.