Year of Publication

2015

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Psychology

First Advisor

Dr. Chana K. Akins

Abstract

Research has indicated that gonadal hormones may mediate behavioral and biological responses to cocaine. Estrogen, in particular, has been shown to increase behavioral responding to cocaine in female rats relative to male rats. The use of Japanese quail may add to our knowledge of sex differences in drug abuse because of their advanced visual system and the ability to control their gonadal hormones via alterations in photoperiod. In three experiments, cocaine-induced behaviors were examined using this avian model.

In Experiment 1, I investigated the potential sex differences in cocaine-induced locomotor activity between male and female Japanese quail and I examined the potential role of gonadal hormones in these effects. Results from Experiment 1 indicated that cocaine-induced locomotor activity correlates with testosterone in male quail. Surprisingly, cocaine-induced activity did not correlate with estradiol in female quail, nor did female quail respond to cocaine as expected. Due to these results, Experiment 2 was designed to determine whether D2 receptors are involved in the psychomotor activating effects of cocaine in female quail. Results from Experiment 2 showed that D2 blockade enhances acute cocaine-induced locomotor activity in female quail. This result suggests that D2 receptors play an important role in cocaine-induced locomotor activity in female quail.

Cocaine’s psychomotor and rewarding properties are typically attributed to different neural mechanisms and are thought to represent different aspects of drug abuse. In Experiment 3, the rewarding properties of cocaine were examined in female quail using a CPP procedure. Additionally, Experiment 3 examined the potential role of estradiol in those effects. Results from Experiment 3 revealed that cocaine is dose-dependently rewarding and estradiol may enhance the rewarding properties of cocaine in female quail.

Taken together, the present work suggests that gonadal hormones may play an important role in both the psychomotor activating effects and rewarding properties of cocaine in Japanese quail. Additionally, the collective results add to our understanding of the underlying hormonal and neurobiological mechanisms that may mediate sex differences in cocaine-induced behaviors.

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