Despite well-known psychoactive effects, the mechanism of action of ethanol in the central nervous system (CNS) is not well understood. Rather than disrupting the integrity of the lipid bilayer of neuronal membranes in a non-specific way, it is becoming increasingly clear that acute exposure to clinical concentrations of ethanol can affect the function of a number of neurotransmitter receptors, such as those for gamma- aminobutyric acid (GABA), glutamate and serotonin. The overall goal of this research project is to contribute to an understanding of the mechanisms by which acute exposure to ethanol modulates the function of ligand-activated channels, specifically, on the modulation of the GABA-A receptor by ethanol. The experiments combine patch clamp electrophysiological and molecular biological approaches and will be conducted using bipolar cells and ganglion cells of the rat retina.
Specific Aim l proposes to test the hypothesis that the GABA-A receptor is a direct target site for the modulatory effect of ethanol and that phosphorylation mediated by intracellular intermediaries can act secondarily to prime the sensitivity of the receptor to ethanol. We will analyze ethanol-induced changes in stationary and non-stationary channel kinetics of the GABA-A receptor and determine whether intracellular dialysis of agents which promote or prevent phosphorylation can influence the outcome of a synergistic interaction between ethanol and GABA.
Specific Aim 2 will test the hypothesis that the subunit composition of the GABA-A receptor is critical in conferring sensitivity to GABA potentiation by ethanol such that neurons whose responses to GABA are potentiated by ethanol can be grouped into predictable patterns of subunit profiles. We will determine by """"""""expression profiling"""""""" the GABA-A receptor subunit composition of those bipolar cells and ganglion cells which have been examined electrophysiologically in Specific Aim 1, using a combination of molecular biological techniques involving antisense RNA (aRNA) amplification and polymerase chain reaction (PCR). In this way, a composite of GABA-A receptor subunits can be revealed from each neuron and this can be correlated with functional data acquired from the same neuron. Overall, this project will contribute to resolving some of the most pressing issues related to ethanol action on GABA inhibitory mechanisms as well as to determining the molecular basis of functional heterogeneity in ethanol-GABA interactions in the mammalian CNS.
| Sapp, D W; Yeh, H H (1998) Ethanol-GABAA receptor interactions: a comparison between cell lines and cerebellar Purkinje cells. J Pharmacol Exp Ther 284:768-76 |
| Yeh, H H; Kolb, J E (1997) Ethanol modulation of GABA-activated current responses in acutely dissociated retinal bipolar cells and ganglion cells. Alcohol Clin Exp Res 21:647-55 |
| Yeh, H H; Grigorenko, E V; Veruki, M L (1996) Correlation between a bicuculline-resistant response to GABA and GABAA receptor rho 1 subunit expression in single rat retinal bipolar cells. Vis Neurosci 13:283-92 |
| Yeh, H H; Grigorenko, E V (1995) Deciphering the native GABAA receptor: is there hope? J Neurosci Res 41:567-71 |
