Senior Theses

Publication Date


Document Type

Thesis (Open Access)

Degree Name

Bachelor of Science in Psychology



Faculty Advisor(s)

Lee Bakner (Thesis Advisor)
Sarah Coste & Tanya Tompkins (Committee Members)

Subject Categories

Applied Behavior Analysis | Behavior and Behavior Mechanisms | Experimental Analysis of Behavior | Psychology


In light of previous work demonstrating that stress can increase subjective drug reward in adult rats, the present study investigated the influence of stress on morphine conditioned place preference (CPP) in early-adolescent, mid-adolescent, and adult male Sprague-Dawley rats. Subjects in each age group were assigned to either a no stress condition or a stress condition in which they were exposed to an unpredictable eight-day schedule of elevated platform and synthetic fox odor stressors. Place conditioning then evaluated subjective morphine reward in all animals. Using a biased procedure, subjects were assigned to receive morphine on the initially non-preferred side of the apparatus and saline on the initially preferred side as identified at pretest. After eight days of conditioning in which drug presentation alternated by day (i.e., morphine one day and saline the next), a post-test was conducted identical to pre-test. Results comparing pre- and post-test time on the non-preferred side indicated no difference between stress conditions or age groups, though place preference was observed in all animals. Activity, scored as midline crosses during conditioning trials, revealed expected habituation to the motor suppressing effects of morphine. Although no effects of stress or age were observed on measures of drug conditioning, the findings suggest that duration between the end of stress exposure and the start of conditioning may have weakened any effect of age-dependent stress on morphine CPP.