CELLULAR-METABOLISM REGULATING H-CURRENT AND M-CURRENT IN BULLFROG SYMPATHETIC-GANGLIA

Much evidence has accumulated suggesting that neurons in autonomic and dorsal root ganglia possess voltage-dependent currents that link with transmitter receptors through intracellular signal transduction systems. The M current (I(M), a voltage-dependent potassium current, was activated at potentials more positive than -65 mV, while the H current (I(H)), a voltage-dependent nonselective cationic current, was activated at potentials more negative than -50 mV. The hydrolyzable form of ATP was required to activate I(M) and I(H). Intracellular application of calmodulin enhanced the amplitude of I(M) in a calcium-dependent manner. I(M) was reduced by W-7, a calmodulin antagonist, and by ML-9. an inhibitor of calmodulin-dependent protein kinase. I(H) was enhanced by intracellular loading with cyclic adenosine monophosphate (AMP) or bath application of forskolin and membrane-permeable cyclic AMP analogues. Isobutylmethylxanthine also increased the maximal conductance of I(H). I(H) was depressed by H-8 but not by phorbol ester. It is concluded that the resting membrane conductance of these ganglion cells can be regulated by basal activities of calmodulin-dependent protein kinase and A kinase.