Cellular metabolism regulating H and M currents 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 (IM), a voltage-dependent potassium current, was activated at potentials more positive than -65 mV, while the H current (IH), a voltage-dependent nonselective cationic current, was activated at potentials more negative than -50 mV. The hydrolyzable form of ATP was required to activate IM and IH. Intracellular application of calmodulin enhanced the amplitude of IM in a calcium-dependent manner. IM was reduced by W-7, a calmodulin antagonist, and by ML-9, an inhibitor of calmodulin-dependent protein kinase. IH 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 IH. IH 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.
Akasu
T
T
Department of Physiology, Kurume University School of Medicine, Japan.
Tokimasa
T
T
D000818:Animals; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D011892:Rana catesbeiana; D015222:Sodium Channels / Q000502:physiology*
D015221:Potassium Channels; D015222:Sodium Channels