Date of Award

Spring 3-27-2025

Embargo Period

4-8-2025

Document Type

Dissertation - MUSC Only

Degree Name

Doctor of Philosophy (PhD)

Department

Neuroscience

College

College of Graduate Studies

First Advisor

John Woodward

Abstract

Approximately 28.9 million people aged 12 and older meet the diagnostic criteria for alcohol use disorder (AUD), characterized by compulsive and frequent alcohol consumption often to avoid negative effects associated with withdrawal. The orbitofrontal cortex (OFC), critical for goal-directed behavior, is disrupted in individuals with AUD. However, the role of specific cell types, such as astrocytes, in regulating alcohol-induced changes in the OFC remains unknown. Previous studies show that acute ethanol inhibits firing of OFC neurons while chronic intermittent ethanol (CIE) exposure increases firing accompanied by enhanced ethanol drinking. The acute ethanol inhibition of OFC neuronal firing is mediated by inhibitory glycine receptors and is reduced by expressing a plasma membrane calcium exporter (PMCA) in OFC astrocytes.

The studies in this dissertation examined the effects of astrocyte PMCA on CIE-induced increases in OFC excitability, the physical interaction between astrocytes and neurons, and alcohol drinking. Adult male and female C57Bl/6J mice were infused in the OFC with an astrocyte specific LCK-GFP or PMCA virus. Separate cohorts of mice underwent 4 weeks of CIE exposure or CIE accompanied with drinking followed by an analysis of OFC neuronal spiking, astrocyte-neuron interaction, and limited access homecage alcohol drinking. A final cohort underwent CIE exposure followed by behavioral testing.

The results suggest that there are sex-dependent differences in how OFC astrocytes and neurons interact and respond to chronic ethanol. For example, CIE increased neuronal firing in male and female LCK-GFP mice compared to Air controls. Interestingly, while PMCA itself increased firing in male Air mice, PMCA reduced CIE-mediated hyperexcitability in females. Similar to spiking, both PMCA and CIE increased the number of GluA1 synapses within the vicinity of astrocytes in males. However, in females, CIE only increased the number of puncta in the PMCA group. CIE did not affect colocalization of astrocytes and GluA1 puncta in male or female controls, but it was elevated in PMCA males. Lastly, CIE exposure increased alcohol consumption in male but not female mice and this was prevented by expressing PMCA in OFC astrocytes. These findings reveal important sex-dependent interactions between OFC astrocyte PMCA and CIE exposure.

Rights

Copyright is held by the author. All rights reserved.

Download

Share

COinS