Date of Award

4-2024

Degree Name

Master of Arts

Department

Psychology

First Advisor

Lisa Baker, Ph.D.

Second Advisor

Cynthia Pietras, Ph.D.

Third Advisor

Sacha Pence, Ph.D.

Keywords

Differential reinforcement of low rate responding, impulsive action, methamphetamine, probiotic

Access Setting

Masters Thesis-Open Access

Abstract

Substance Use Disorder (SUD) is a chronic, debilitating condition often comorbid with anxiety and depression. Both SUD and affective disorders are characterized by cognitive dysfunction, including impaired decision-making and impulsivity. A mounting body of research implicates gut microbiome alterations as a contributing factor to the pathophysiology of affective disorders. No published studies have assessed behavioral effects of dietary interventions targeting psychostimulant-induced gut microbiome changes. The present study utilized a differential reinforcement of low rate responding schedule (DRL 18 s) as a behavioral index of drug-induced impulsive action to determine if a dietary probiotic supplement alters the behavioral effects of (+)-methamphetamine in rats. Thirty-two adult male Sprague-Dawley rats were trained to lever press for food reinforcement under a DRL 18 s schedule. Rats were then assigned to two dietary treatment groups, matched on reinforcement rate; the supplement group received continuous access to Bio-Kult Advanceâ in their drinking water and the control group received standard drinking water. Half the rats in each diet group received intraperitoneal injections of 1 mg/kg (+)-methamphetamine and the remaining rats received saline injections for eight consecutive days. DRL 18 s test sessions were conducted on day 1 and day 8, and subsequently 24 h, 48 h, 96 h, after the last injection. Statistically significant increases in response rate and corresponding decreases in reinforcement rate were observed in (+) methamphetamine-treated animals compared to saline-treated animals. The probiotic-treated rats displayed a higher drug-induced increase in response rate, but reinforcement rates were comparable between diet groups, and the main effect of diet was not statistically significant.

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