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UBC Theses and Dissertations

A modifed version of the defensive burying paradigm exposes group differences in behavior, vasopressin and c-fos expression in testosterone-replaced rats Maynard, Kyle


Testosterone has been shown to have marked effects on different types of coping behaviors. The current study was done to test the capacity by which testosterone alters the amount of defensive burying in the defensive burying paradigm. Twenty high and twenty low testosterone-replaced (T), castrated rats were used to determine the effects of testosterone using a modified version of the defensive burying paradigm. Rats were exposed to either a remotely triggered mousetrap (snap), or neutral trap (yoke), creating four groups; high-T snap, high-T yoke, low-T snap and low-T yoke. Under habituation conditions, both high- and low-T replacement groups show a characteristic behavioral profile that indicated they habituated. As a function of testosterone replacement, animals showed significantly less burying but more rearing with high-T compared to low-T replacement (p = 0.004 and p = 0.02, respectively). Under aversive trap conditions, testosterone showed a general effect to decrease burying behavior. Testosterone affected rearing behavior that was highest within high-T groups and with direct exposure to the snap. There were limited neurochemical effects of testosterone other than a significant increase in vasopressin mRNA expression in high-T compared to low-T animals in both the medial amygdala and posterior bed nucleus of the stria terminalis. In addition, animals that were exposed to either test condition showed higher c-Fos activation in the septum compared to transport controls. These results show that high testosterone replacement can reduce signs of neophobia, alter the magnitude of adaptable behaviors and promote proactive exploration under aversive conditions.

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