GluD1 regulation of structural plasticity in chronic ethanol exposure and protracted withdrawal

Des Moines Univ Osteopathic Medical Ctr, Des Moines IA

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Abstract

Project Summary Long-lasting vulnerability to relapse is a major hurdle to achieving successful treatment outcomes in persons with a substance use disorder. The glutamate receptor system is highly implicated in the development and maintenance of functional and structural alterations driving a return to drug use. Increasing our understanding of glutamatergic regulation of neurobiological alterations during drug use and withdrawal, we propose to explore a new target for the development of therapeutic agents. Delta-type ionotropic glutamate receptors (GluD) have been identified as regulators in the formation of synaptic connections, as they serve to regulate the alignment and development of dendritic spines. A recent study has indicated that GluD1 receptor function/expression plays a role in structural plasticity in a model of psychostimulant use. It is currently unknown what role GluD1 plays in altering structural plasticity following chronic ethanol exposure or protracted withdrawal. Using an ethanol exposure model this application seeks to identify the role GluD1 holds in the regulation of dendritic spine density and morphology under ethanol exposure and after protracted withdrawal. We will focus on the basolateral amygdala (BLA), a key region for ethanol action. We hypothesize that GluD1 dynamically controls chronic ethanol- and withdrawal-associated changes in spine morphology in the BLA. We will test this hypothesis in one Specific Aim, comprised of three independent experiments. All experiments will compare male and female rats. First, we will characterize dendritic spine morphology under control conditions, ethanol exposure, and across various withdrawal time points (day 1, 21, 42), using iontophoretic dye injection and confocal microscopy methods. We will also characterize GluD1 expression in surface membrane fractions using a biotinylation procedure followed by western blot analysis at each experimental time point. Finally, we will utilize dye injections and confocal microscopy paired with injection of a shRNA viral construct to knock down GluD1 levels in the BLA prior to ethanol exposure. This experiment will identify the specific role GluD1 plays in dendritic spine expression and morphology across our treatment groups and sex. Together, these studies will reveal the role of GluD1 in regulation of structural plasticity during ethanol exposure and withdrawal. As such, GluD1 regulation of structural plasticity could contribute to well characterized functional alterations of the glutamatergic receptor system during short term withdrawal. This would implicate GluD1 as a key hub, capable of regulating functional and structural plasticity, making it a promising target for therapeutic development. Long term objectives are to identify the overall impact of GluD1 regulation on both structural and functional plasticity across additional brain regions impacted by drug taking and withdrawal.