Inhibition of drug-gated chloride currents by calcium influx in frog sensory neurons

Anoxic block of GABAergic IPSPs

In rat hippocampal slices GABAergic IPSPs are very rapidly suppressed by anoxia (in less than 2 min). Both early (GABAA) and late (GABAB) components are affected. After reoxygenation, the IPSPs recover, but only slowly and not always completely. Iontophoretic applications of GABA or baclofen indicated no major depression of responses during anoxia. It is therefore unlikely that the anoxic suppression of IPSPs is caused by desensitizations of GABA receptors. A more probable explanation is a failure of GABAergic neurons to release GABA from inhibitory nerve terminals.

Ethanol enhancement of GABA-activated chloride current in rat dorsal root ganglion neurons

The acute effects of ethanol on the gamma-aminobutyric acid (GABA)-activated current were studied with the rat dorsal root ganglion neurons in primary culture using the whole-cell patch-clamp technique. GABA produced an inward chloride current, which was composed of an initial transient and a subsequent sustained phase. Ethanol at concentrations ranging from 30 to 300 mM enhanced the transient current in a concentration-dependent manner without affecting the sustained current.

Alpha-chloralose opens the chloride channel of frog isolated sensory neurons

The effect of alpha-chloralose on the sensory neurons isolated enzymatically and mechanically from frog dorsal root ganglia was studied using a suction-pipette technique. The threshold concentration of alpha-chloralose was around 3 x 10(-5) M and the current produced by alpha-chloralose saturated at the concentration of 3 x 10(-3) M or more. The dose-response curve for alpha-chloralose provided a Ka value of 6 x 10(-4) M and a Hill coefficient of 1.8. The reversal potential of the response elicited by alpha-chloralose was close to the equilibrium potential for Cl- (ECl), indicating that the current was carried through Cl- channels. The current-voltage relationship indicated that there was little voltage dependence in the alpha-chloralose-induced response. The analysis of the variance of the alpha-chloralose-induced Cl- current fluctuations showed two types of the receptor-ionophore complexes with different channel conductances.