Date of Award

8-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Rebecca A. Prosser

Committee Members

Jim Hall, John Koontz, Matthew Cooper, Jae Park

Abstract

Alcohol abuse induces many disorders including depression, metabolic syndrome, and sleep disturbances. The strong link between alcohol abuse and sleep problems, along with the close connection between sleep and circadian rhythms, led us to investigate ethanol’s effects on the circadian clock. Previous work has shown that acute ethanol blocks photic phase shifts in vivo and glutamatergic phase shifts in vitro. However, neural systems become tolerant to ethanol across different timeframes. Despite both ethanol tolerance and ethanol withdrawal syndrome being listed as criteria for developing alcohol use disorders, little is known about how ethanol tolerance and withdrawal induced hyperexcitability develop and how they differ. Because previous work has shown that acute tolerance to ethanol occurs in the SCN, we tested whether additional forms of tolerance as well as withdrawal induced sensitization develop in the SCN and we identified distinct changes across all of these conditions with respect to N-methyl-d-aspartate (NMDA) receptor related proteins. Our hypotheses were that rapid tolerance, chronic tolerance, and withdrawal induced sensitization occur in the SCN, that these conditions are associated with increased expression of NR2B containing NMDA receptors, and that the extent to which these changes occur differ across tolerance and withdrawal paradigms. We found that rapid tolerance develops in vivo and in vitro with respect to a loss in phase shift inhibition. Additionally, we have discovered chronic tolerance and withdrawal induced sensitization to glutamate also occur in vitro. Furthermore, we compared phosphorylation and total expression of NMDA receptor subunits and NMDA receptor-regulating proteins across the drinking models that induce rapid tolerance, chronic tolerance, or withdrawal. We found no changes during rapid tolerance to ethanol. In contrast, we saw an increase in the ratio of total expression of NR2B/NR2A during both chronic tolerance and withdrawal from EtOH, an increase in Tyr 1472 phosphorylation during withdrawal, and an increase in mature BDNF and TrkB phosphorylation during withdrawal. Altogether we demonstrated the power of utilizing the SCN for investigating ethanol induced plasticity by identifying rapid tolerance, chronic tolerance, and withdrawal induced sensitization. Additionally we found that the cellular effects of ethanol during these forms of tolerance and withdrawal differ.

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