Semester

Summer

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Psychology

Committee Chair

Karen G. Anderson

Committee Member

Kathryn Kestner

Committee Member

Melissa Blank

Committee Member

Mariya Cherkasova

Committee Member

Tim Nurkiewicz

Abstract

Ethanol (EtOH) and nicotine (NIC) are among the most commonly used and co-used drugs in the world. Co-use occurs in people who use one or both drugs chronically, but also in people who only consume one or both drugs acutely, often in a “bingeing and chipping” pattern. Given that each drug on its own has previously been shown to affect impulsive choice in delay-discounting procedures, with some indication that drug effects could vary by sex, the purpose of the present experiments was to investigate effects of combined EtOH and NIC at a range of dose combinations on delay discounting in male and female Sprague-Dawley rats. Eight rats of each sex (n = 16) were trained on a two-lever delay-discounting procedure until choice for the larger, delayed reinforcer was stable. In Experiment 1, EtOH alone (0-3.0 g/kg; p.o.) was tested; in Experiment 2, NIC alone (0-1.0 mg/kg; s.c.) and combined EtOH and NIC were tested. In both experiments, mixed ANOVAs were conducted to assess effects of sex, drug dose, session block, and delay series on choice for the larger reinforcer. Combination indices were calculated to assess the nature of combined drug effects. No significant sex differences were observed at baseline or following drug administration, but four female rats were on a shortened delay series. EtOH alone (2 and 3 g/kg) and NIC alone (0.3 mg/kg) both reduced choice for the larger reinforcer (i.e., increased impulsive choice) relative to vehicle. When the drugs were combined, percent choice for the larger reinforcer was reduced relative to vehicle. In general, combinations of the two drugs reduced choice for the larger reinforcer relative to each drug alone. Combination indices indicated that EtOH and NIC together exerted an antagonistic effect, with the combined effect less than the sum of its parts. Future directions include administering EtOH intragastrically, reversing the order of drug administration, and increasing the sample size to allow for variation in baseline discounting rates.

Embargo Reason

Publication Pending

Available for download on Wednesday, May 21, 2025

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