Main Research Component 2: Binge-type alcohol exposure during adolescence alters the septohippocampal circuit during advanced aging

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PROJECT SUMMARY/ABSTRACT MAIN RESEARCH COMPONENT 2 Converging data from human studies and preclinical animal models have revealed that alcohol binge drinking/exposure during early adolescence is associated with changes in brain structure and connectivity. Persistent brain damage after adolescent intermittent ethanol exposure (AIE) in rodents, a model of binge drinking, entails reduced hippocampal neurogenesis and a loss of cholinergic neurons in the medial septum and diagonal band of Broca (MS/DB). The circuit formed between those regions, the septohippocampal pathway, is critical for learning and memory. The cholinergic projections from the MS/DB to the hippocampus are arranged in a highly topographical pattern, but pilot data suggest a loss of neurogenesis in the hippocampus disrupts the unique somatotopic organization during the aging process. Furthermore, we observed that as rats aged following AIE, a spatial memory impairment emerged, which was paralleled by a reduction in activity-related acetylcholine release within the hippocampus. The goal of this proposal is to reveal how heavy intermittent alcohol exposure during adolescence alters brain connectivity, neural plasticity and behavioral function across the lifespan. Specifically, we will determine how aging following AIE (a) alters the topographical organization of the cholinergic septohippocampal pathway and impedes the expression of cholinergic neural phenotypes within the MS/DB, which modulate activity-dependent hippocampal acetylcholine release (Aim 1); (b) disrupts the neurophysiological profile of cholinergic septohippocampal pathway and leads to behavioral and acetylcholine dysfunction across septotemporal axis of the hippocampus (Aim 2). Finally, given that the septohippocampal circuit is extremely pliable to environmental conditions, we will use exercise as a tool to restore hippocampal neurogenesis, prevent MS/DB cholinergic atrophy/cell loss, and halt dysfunctional remapping to the hippocampus, caused by aging with AIE, which we hypothesized leads to impaired spatial behavior and blunted activity-dependent acetylcholine release (Aim 3). Our preliminary data revealed a profile of septohippocampal dysfunction that resembled alcohol-related dementia as rats exposed to AIE begin to age, and the goal of this proposal is to understand this complex process so it can be corrected to reduce the risk of cognitive dysfunction and unsuccessful aging.