Date of Award

6-2024

Degree Name

Doctor of Philosophy

Department

Psychology

First Advisor

Lisa Baker, Ph.D.

Second Advisor

Alan Poling, Ph.D.

Third Advisor

Cynthia Pietras, Ph.D.

Fourth Advisor

Matthew Baggott, Ph.D.

Abstract

3,4-Methylenedioxymethamphetamine (MDMA) has been abused recreationally in the rave scene for decades. As pharmacotherapy research has progressed to develop alternative medications to treat trauma-related psychiatric symptoms, MDMA has become a prime candidate for medication-assisted psychotherapy in the treatment of PTSD and will soon be FDA approved for medicinal use. Despite convincing evidence for favorable clinical outcomes, this substance has been known to contribute to acute depressive states following excessive use. The sharp decrease in mood and cognitive impairment following MDMA use is colloquially termed Blue Mondays. Measuring lack of motivation or more broadly anhedonia through withdrawal of acute and chronic MDMA use has great utility to understanding the underlying neurophysiology associated with depression and drug-induced changes in affect in humans and animals. This study attempted to establish a preclinical model to evaluate the Blue Mondays phenomenon to gain a better understanding of the consequences of binge MDMA use on motivated behavior. In this study, 16 adult male Sprague-Dawley rats were trained under a geometric progressive ratio (PR) schedule of food reinforcement for 12 weeks. Two groups of rats were matched based on baseline breakpoints, then randomly assigned to either MDMA (7.5 mg/kg, I.P.) or saline treatment. Three injections were administered in a binge-like fashion with two-hour intervals between injections on two occasions, two weeks apart. Rats were then tested 24 hours after the last dose and for seven consecutive days following each binge-dose. Breakpoints, response rates, and reinforcers earned were recorded during each session. The research hypothesis assessed was that MDMA treatment would reduce motivation for food reinforcers, as indicated by a reduction in the breakpoint and the number of reinforcers earned. Results indicated no statistically significant differences between MDMA-treated and saline-treated rats on breakpoint, reinforcers earned, or response rate. Additional studies addressing the methodological limitations of the current study are warranted to further evaluate this approach to modeling motivational changes associated with binge dosing and withdrawal. Continuing this line of research may contribute to our understanding of how MDMA and related substances impact mood regulation and reward processing and can inform the development of therapeutic strategies that use psychostimulants to mitigate depressive symptoms.

Access Setting

Dissertation-Open Access

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Psychology Commons

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