Ethanol modulation of GABA-activated current responses in acutely dissociated retinal bipolar cells and ganglion...

This study examined the effect of acute ethanol exposure on GABA-activated whole-cell current responses elicited in bipolar cells and ganglion cells of the rat retina. Acute exposure to ethanol potentiated GABA responses in 86% of the bipolar cells and in 52% of the ganglion cells tested. As determined in bipolar cells, ethanol was maximally effective at a concentration of 50 mM. In bipolar cells, a GABAC receptor-mediated component of the whole-cell response to GABA could be uncovered which was also potentiated by ethanol. However, ethanol was ineffective in enhancing bipolar cell responses to glycine. GABA-activated current responses monitored in ganglion cells that were insensitive to modulation by ethanol were sensitive to potentiation by diazepam. At higher concentrations (100-175 mM), ethanol by itself occasionally induced a chloride-mediated current but this occurred independent of an ethanol-induced potentiation of GABA responses. These data establish that ethanol can modulate the sensitivity of retinal neurons to GABA. Overall, the results presented in this study set the stage for future studies to examine the cellular and molecular bases for a differential neuronal sensitivity to an ethanol-induced modulation of GABA responses.