Ethanol and Persistent Activity in Prefrontal Cortex

Medical University Of South Carolina, Charleston SC

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Abstract

Alcoholism is characterized by a loss of control over drinking that may result from long-lasting alterations in[unreadable] higher cortical circuits that normally control compulsive behaviors. Brain imaging studies show that, in[unreadable] alcoholics, the prefrontal cortex (PFC) displays functional alterations during abstinence or after exposure to[unreadable] ethanol (EtOH) or visual cues associated with drinking. Little, however, is known about the actions of EtOH[unreadable] on prefrontal function at the cellular level. In this project, we will investigate the effects of acute and chronic[unreadable] EtOH exposure on the function of excitatory pyramidal neurons of the prefrontal cortex. A hallmark of[unreadable] prefrontal cortical neurons is "persistent activity" characterized by spontaneous and rhythmic transitions[unreadable] between a hyperpolarized down-state in which firing is inhibited and a depolarized up-state that is conducive[unreadable] for generating action potentials. The firing activity during up-state periods is modulated by dopaminergic[unreadable] input from VTA neurons that synapse on layer V prefrontal cortical neurons. Persistent activity may allow[unreadable] the prefrontal cortex to exert higher-order control over the addiction neurocircuitry by integrating and[unreadable] processing sensory information derived from internal and external cues. Disruption of persistent activity[unreadable] states within the prefrontal cortex by EtOH may be a primary event in the loss of control over compulsive[unreadable] drinking behaviors. Persistent activity has been studied in anesthetized whole animals but it does not occur[unreadable] in reduced systems such as acutely isolated slices of cortex. To circumvent problems associated with[unreadable] anesthesia and to allow for precise analysis of putative mechanisms, we have adapted a slice co-culture[unreadable] system containing prefrontal cortex, VTA, and hippocampus. After 2 weeks in culture, prefrontal neurons in[unreadable] this system display robust and reproducible patterns of persistent activity that can modulated by stimulusevoked[unreadable] firing of VTA dopamine neurons. The major goal of this project is to determine the effects of acute[unreadable] and chronic ethanol exposure on persistent activity of PFC neurons using this co-culture system. Aims 1, 2[unreadable] and 3 will use patch-clamp electrophysiology to analyze the effects of acute and chronic ethanol on[unreadable] spontaneous and VTA-evoked persistent activity in layer V prefrontal pyramidal neurons. Aim 4 will use[unreadable] confocal imaging techniques to assess the effects of ethanol on pyramidal cell activity at the network level.[unreadable] The results of these studies will yield important new information regarding ethanol's effects on brain function.