Role of the GTP‐Binding Protein Go in the Suppressant Effect of Ethanol on Voltage‐Activated Calcium Channels of Murine Sensory Neurons

Abstract

Whole-cell and single-channel recording techniques were used to investigate the acute, in vitro effects of ethanol on the function of voltage-activated Ca2+ channels in cultured neurons derived from dorsal root ganglia (DRG) of embryonic mice. Although 5.4 mM ethanol produced a sustained increase of the amplitude of the whole-cell Ca2+ current (ICa), 43.2 mM ethanol had a time-dependent biphasic effect. That is, within 0.5 min of exposure to 43.2 mM ethanol, the maximal amplitude of ICa initially increased before declining to a new steady-state value. As anticipated, the facilitatory and inhibitory effects of ethanol on ICa were associated with an increase and decrease, respectively, in the probability of single-channel open events. Pretreatment of DRG with 200 ng/ml of pertussis toxin abolished the inhibitory, but not the facilitatory, effect of 43.2 mM ethanol on ICa. Pretreatment with pertussis toxin also prevented the reduction of the probability of single-channel opening caused by 43.2 mM ethanol. Similarly, dialysis of neurons with polyclonal antibodies against the alpha-subunit of G(o) but not Gs, abolished the inhibitory effect of 43.2 mM ethanol on ICa. These data demonstrate concentration- and time-dependent biphasic effects of ethanol on the activity of Ca2+ channels. The inhibitory effect of ethanol requires activation of the alpha-subunit of G(o), which then decreases the probability of Ca2+ channel opening.