Date of Defense

4-18-2025

Date of Graduation

4-2025

Department

Psychology

First Advisor

Lisa Baker

Second Advisor

Alan Poling

Keywords

impulsivity, amphetamine, DRL schedule, response inhibition, psychostimulants, operant conditioning

Abstract

Impulsivity, a core component of substance use disorders (SUDs), is often modeled in preclinical research using differential reinforcement of low-rate responding (DRL). DRL schedules require subjects to withhold responding for a specified interval to obtain reinforcement and are highly sensitive to the disruptive effects of psychostimulants such as amphetamine. Although prior studies have shown that amphetamine disrupts DRL performance by increasing response rates and reducing reinforcers earned, the role of training history in modulating these effects remains unclear. The present study assessed whether prior experience with short (DRL 18-s), intermediate (DRL 36-s), or long (DRL 72-s) schedules influences sensitivity to amphetamineinduced impulsivity. Twenty-four adult male Sprague-Dawley rats were trained under one of the three DRL schedules until stable performance was achieved. Animals were then tested on both DRL 18-s and DRL 72-s schedules following intraperitoneal injections of saline, 0.5 mg/kg, and 2.0 mg/kg d-amphetamine. Amphetamine produced the expected increase in response rates and shift toward shorter interresponse times. However, rats trained on the DRL 18-s schedule demonstrated reduced sensitivity to these disruptions, earning more reinforcers and maintaining a higher proportion of responses than rats trained on the DRL 72-s schedule. These findings suggest that shorter DRL training histories may establish more resilient inhibitory control patterns and highlight the importance of behavioral history in determining drug sensitivity. This research has implications for understanding individual differences in impulsivity and for developing behavioral interventions that reduce vulnerability to drug-induced behavioral dysregulation.

Access Setting

Honors Thesis-Restricted

Restricted to Campus until

6-11-2027

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Available for download on Friday, June 11, 2027

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