Doctor of Philosophy
Psychology, General Experimental
Date of Defense
George T. Taylor, PhD
One Animal paradigm used to study addiction is conditioned place preference. CPP is achieved when an animal develops a preference for environmental stimuli previously paired with subjective effects of a rewarding drug. Women may experience greater drug sensitivity than men, most likely due to estrogen levels. The purpose of this experiment was to assess the effects of female sex hormones on drug sensitivity and their interaction with the primary factors causing relapse, stress or drug re-exposure. Female rats were ovariectomized and received replacement hormones to control circulating hormone levels. These groups of animals were tested for amphetamine (AMPH)-induced CPP and the rate of CPP extinction before and after a challenge. The challenge came in the form either of AMPH re-exposure or restraint stress. The results indicated that 1 mg/kg body weight AMPH results in significant CPP, but the different hormone treatments did not differentially influence the magnitude of CPP. However, the overall time spent in the drug-paired compartment during the extinction phase was greatest for animals treated with estrogen, while the progesterone group spent the least. These findings suggest that estrogen treatment results in greater resistance to extinction. Both the stress and drug challenges resulted in reinstatement of CPP. However there was no statistically significant difference between the two challenge conditions in the magnitude of CPP reinstatement. During the second extinction phase, the animals that received the drug challenge met the criteria for extinction, whereas those that received the stress challenge did not. The suggestion is that the effect of a single stress on drug-seeking behaviors may be more long lasting than a single drug exposure. These findings provide evidence for the hypothesis that estrogen enhances resistance to extinction of a drug preference response and progesterone suppresses it. Also, both stress and drug exposure are significant triggers for the reinstatement of extinguished drug-seeking behavior, and the effects of stress may be more prolonged than drug exposure. These conclusions suggest that drug treatment of women may need to be specialized with consideration of hormone status, and that drug treatment for men and women should include stress management.
Bleile, Melissa Elaine, "Female Hormonal Influences on Stress- and Drug-induced Reinstatement of Extinguished Amphetamine-induced Conditioned Place Preference" (2006). Dissertations. 606.