Reciprocal changes in corticosterone and testosterone levels following acute and chronic handling stress in the tree lizard, Urosaurus ornatus.

To examine the reciprocal interactions among gonadal and adrenal steroid secretion, male tree lizards (Urosaurus ornatus) were subjected to two forms of stress. They were subjected either to the acute stress of being held in collecting bags for up to 4 hr or to the chronic stress of being maintained in individual cages in the laboratory for up to 3 weeks. In both cases, levels in stressed animals were compared to levels in free-living animals as controls. Under both conditions plasma levels of corticosterone increased and plasma levels of testosterone decreased compared to free-living controls. The response to the acute stress was much greater for both hormones than to the chronic stress, although in both cases testosterone levels changed less in response to stress than corticosterone levels. The corticosterone response to acute stress was extremely rapid with levels increasing over six-fold in the first 10 min. Plasma levels of corticosterone and testosterone were negatively correlated among individuals in the chronic stress experiment, but not in the acute stress experiment. This correlational evidence is consistent with the hypothesis of a direct effect of corticosterone levels on testosterone levels and suggests that these may only be expressed under some conditions.