Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Ronald H. Peters


Yohimbine, an alpha[subscript]2 noradrenergic antagonist, facilitates the copulatory behaviors of male rats when these behaviors have been associatively inhibited by lithium chloride induced aversive contingencies (the copulation-illness association or C-IA paradigm). This facilitation is not evident on initial acquisition trials, but only after inhibition of copulatory behaviors. This initial lack of facilitation may reflect a ceiling effect produced by high baseline levels of copulatory behaviors. Alternatively, the physiological state induced by yohimbine may initially attenuate the facilitory effects of the drug. In Experiment 1, the copulatory behaviors of male rats were partially inhibited prior to administration of yohimbine (2.0 mg/kg). Additionally, half of the subjects received yohimbine experience outside of the context of the copulation test. Yohimbine did not facilitate copulatory behaviors in animals whose copulatory behaviors had been partially inhibited or in animals with prior experience with the drug. These findings suggest that the failure of yohimbine to facilitate copulatory behaviors during initial C-IA acquisition trials cannot be attributed to either high baseline levels of copulatory behaviors or initial physiological effects of yohimbine. Experiment 2 examined the effects of a pharmacological manipulation (the dopaminergic antagonist apomorphine; 150, 300, and 450 ug/kg) known to facilitate copulatory behaviors in other paradigms. Apomorphine (150 ug/kg) facilitated copulatory behaviors in the C-IA paradigm during extinction but not acquisition. Non-copulatory effects (e.g., reinforcement, emetic) of apomorphine may attenuate the ability of this drug to facilitate copulatory behaviors in testing situations containing aversive elements.



Digital Repository @ Iowa State University,

Copyright Owner

Mark Patrick Bowes



Proquest ID


File Format


File Size

76 pages