CELLULAR MODELS OF DEPENDENCE USING BRAIN SLICES

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This project proposes to continue cellular studies of the role of synaptic transmitters and their receptors in alcohol intoxication and addiction. The rationale behind this approach is the considerable literature showing the synapse as the most sensitive site of ethanol action, and particularly those mediated by glutamate and GABA release. Our past studies lead us to hypothesize a role for presynaptic opiate and GABA/B receptors and postsynaptic NMDA and GABA/A receptors in ethanol intoxication and dependence. Our rationale is also based on behavioral findings with abused drugs, including alcohol, suggesting that the nucleus accumbens (NAcc) and amygdala are key areas in the reinforcing properties of these drugs, and that these properties may involve the same transmitter candidates, among others. We propose four sets of experiments: 1) To examine the effects of chronic ethanol treatment (via the ethanol vapor inhalation method) and withdrawal on membrane and synaptic properties in NAcc core and shell and amygdala neurons; 2) To examine synaptic and membrane properties in NAcc core and shell and amygdala neurons in an animal model of 'relapse' or protracted abstinence, whereby rats are treated chronically with ethanol vapor and then withdrawn for 7-14 days (at a time when 'craving' would be maximal); 3) To continue studies of the effect of the 'anti-alcoholism' drug acamprosate on NMDA and GABA/b receptors in NA/cc neurons, but now in the relapse model of specific aim #2; 4) To initiate normative in vitro studies of acute and chronic ethanol on membrane and synaptic properties of accumbens neurons in the mouse, for later studies of murine 'relapse' and genetic models. These studies will use hippocampal, NA/cc and amygdala brain slices and involve standard intracellular and "patch-slice" whole- cell clamp methods. We will use the infrared videomicroscopic method to distinguish morphologically different cell types for comparison to electrophysiological properties. We will examine evoked, pharmaco- logically-isolated monosynaptic events, responses to exogenous transmitters, paired-pulse inhibition and spontaneous synaptic events, to test the specificity and site of ethanol action. We believe these studies will provide important new information on possible sequelae of ethanol dependence at the cellular level, and--by virtue of comparisons of ethanol and acamprosate actions in control and protracted abstinence models--will also provide clues as to the cellular and ion channel correlates of alcohol seeking behavior.