Objectives Determine whether plasma cortisol levels are altered by ovariectomy and by the ovarian cycle in female marmosets. In contrast to many species, in which social subordination is associated with elevated glucocorticoid levels, subordinate female common marmosets exhibit lower plasma cortisol levels than dominant females. We have previously reported that this cortisol difference appears to be mediated by reproductive activity, as subordinate females are typically anovulatory. In this study, we further examined the interactions between reproductive function and plasma cortisol. Subjects were 6 females undergoing ovulatory cycles, 5 acyclic subordinate females housed in groups of unrelated adults, and 6 long-term ovariectomized females housed in mixed-sex pairs. Beginning in the cycling animals' early follicular phase, basal blood samples were collected daily for 16 days and at 2- to 3-day intervals for an additional 16 days. Samples were collected at 0900 h and were assayed for cortisol, progesterone, and lutenizing hormone. Cyclic, but not acyclic or ovariectomized, females exhibited significant changes in cortisol levels across the sampling period. Cortisol rose progressively through the follicular phase, peaked during the periovulatory period, and declined across the luteal phase. Cortisol levels of acyclic and ovariectomized females were significantly lower than those of cycling females only during the cycling animals' periovulatory period. Moreover, ovariectomized females tended to have somewhat higher cortisol levels than acyclic females. These results provide further evidence that circulating cortisol titers correlate with patterns of ovarian activity in female marmosets. Furthermore, they suggest that social subordination may also exert direct suppressive effects on cortisol levels, independent of its effects on reproduction. Key Words dominance, ovarian cycle, ovariectomy
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