The Journal of Neurophysiology Vol. 84 No. 1 July 2000, pp. 247-254
Copyright ©2000 by the American Physiological Society

Chronic Exposure to Ethanol Alters GABA_A Receptor-Mediated Responses of Layer II Pyramidal Cells in Adult Rat Piriform Cortex

 ¹Program in Neuroscience and  ²Department of Pharmacology, University of Connecticut Health Center, Farmington, Connecticut 06030

Signore, Armando P. and Hermes H. Yeh. Chronic Exposure to Ethanol Alters GABA_A Receptor-Mediated Responses of Layer II Pyramidal Cells in Adult Rat Piriform Cortex. J. Neurophysiol. 84: 247-254, 2000. This study examined the effect of chronic exposure to ethanol on -aminobutyric acid type-A (GABA_A) receptor-mediated responses of layer II pyramidal neurons of the piriform cortex. Slices containing the piriform cortex were derived from pair-fed adult rats maintained on ethanol-supplemented or control liquid diet for 30 days. Responses of identified layer II pyramidal neurons to exogenously applied GABA were monitored by whole-cell patch-clamp recording. Chronic exposure to ethanol resulted in a rightward shift in the EC₅₀ of GABA and a decrease in the amplitude of maximal GABA response. GABA-induced responses were modulated by acutely applied ethanol (10-100 mM) in both chronic ethanol-treated and control groups. No significant difference was found in the average change in GABA response, suggesting that tolerance to acute ethanol exposure did not develop. When the modulatory responses of individual cells were classified and grouped as either being attenuating, potentiating, or having no effect, the incidence of potentiation in the ethanol-treated group was significantly higher. Consistent with the absence of tolerance to acute ethanol, cross-tolerance to diazepam was not observed following 30 days of treatment with ethanol. These results are discussed in light of regionally specific effects of chronic ethanol treatment on GABA_A receptor-mediated responses of layer II piriform cortical neurons.