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Glucocorticoids and agonistic responding in male golden hamsters: A behavioral, neuroanatomical and neurochemical analysis
Abstract
This thesis research was designed to study the role of glucocorticoids in the central regulation of aggressive, submissive, and communicative behavior in male golden hamsters (Mesocricetus auratus). It represents the first time that site-, context-, dose-, and steroid-specific actions of glucocorticoids in behavioral regulation have been systematically examined within the central nervous system. Chronic implants of cortisol exerted site-specific and context-dependent effects on agonistic responding within the hypothalamus. In paired encounters with aggressive opponents, submissive responding was induced by cortisol implants in the medial preoptic area, anterior hypothalamus, and ventromedial hypothalamus; aggressive responding by implants in the paraventricular nucleus and third ventricle. Cortisol implants in the anterior hypothalamus induced submissive responding in paired encounters with aggressive opponents, aggressive responding in paired encounters with submissive opponents, and aggressive responding in territorial aggression tests with juvenile intruders. Acute microinjections of cortisol in the anterior hypothalamus exerted dose-dependent and steroid-specific effects on agonistic responding. High (10$\sp{-2}$M) doses of cortisol induced submissive responding; low (10$\sp{-6}$M) doses induced aggressive responding. The direction of these biphasic effects were unique to cortisol. High doses of deoxycorticosterone induced aggressive responding, while both high and low doses of testosterone, dihydrotestosterone, progesterone and estradiol had no effect. Low doses of deoxycorticosterone also had no effect. Acute peripheral administration of cortisol induced aggressive responding, as did chronic administration of the glucocorticoid synthesis inhibitor cyanoketone. In contrast, central and peripheral administration of the antiglucocorticoid RU486, had significant site- and dose-dependent effects hypothalamic-pituitary-adrenal axis function, but no effect on agonistic responding. In all cases, the effects of cortisol on flank marking behavior appeared to relate more to the social status of the cortisol-treated animal than a direct effect on the neural substrates of flank marking. Dominant animals flank marked at higher, and subordinate animals at lower levels than their opponents. In conclusion, glucocorticoids are prepotent modulators of agonistic responding within the medial hypothalamus. Both acute and chronic neuroendocrine regulation of agonistic responding by adrenal steroids appear to serve the function of promoting adaptive behavioral responses that minimize the risk of serious injury during competitive interactions.
Subject Area
Neurosciences|Behavioral psychology
Recommended Citation
Hayden-Hixson, Diane Conrad, "Glucocorticoids and agonistic responding in male golden hamsters: A behavioral, neuroanatomical and neurochemical analysis" (1991). Doctoral Dissertations Available from Proquest. AAI9132862.
https://scholarworks.umass.edu/dissertations/AAI9132862