The action of a phorbol ester on voltage-dependent parameters of the sodium current in isolated hippocampal neurons.
The action of a phorbol ester (phorbol-12,13-diacetate) on the voltage-activated sodium current has been investigated by the voltage-clamp method in acutely isolated pyramidal neurons from rat hippocampus. The intracellular perfusion of isolated pyramidal neurons for 30-40 min induced a gradual 10-15 mV shift in both the current-voltage relationship and voltage-dependent steady-state inactivation to more negative potentials. The application of phorbol ester (1-10 microM) to isolated neurons for the same time increased the amplitude of sodium current by 15-20%, shifted the above-mentioned voltage-dependent parameters for an additional 10-15 mV in the same direction and changed the slope of the steady-state inactivation curve. In contrast, after prolonged incubation of slices in the phorbol ester-containing solution (1-10 microM) for 0.5-3 h, subsequent application of phorbol ester at the same concentration caused neither the addition shift of the voltage-dependent characteristics of sodium channels nor the change of the slope of the steady-state inactivation curve. However, in this case an increase in the amplitude of sodium current by 15-20% during 30-40 min intracellular perfusion was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Chizhmakov
I V
IV
A. A. Bogomoletz Institute of Physiology, Kiev, Ukraine.
Klee
M R
MR
D000818:Animals; D000831:Animals, Newborn; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010477:Perfusion; D010703:Phorbol Esters / Q000494:pharmacology*; D051381:Rats; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*
D010703:Phorbol Esters; D015222:Sodium Channels; C008874:phorbol-12,13-diacetate