ADRENAL AXIS ACTIVATION BY CHRONIC SOCIAL STRESS FAILS TO INHIBIT GONADAL-FUNCTION IN MALE RATS

Stress in males via the hypothalamic-pituitary-adrenal (HPA) axis may set into motion varied physiological alterations, including dysfunctio n of the hypothalamic-pituitary-gonadal (HPG) axis. However, the influ ence of the HPA on the HPG axis may not always be inhibitory. Presence or absence of stimuli of sexual significance that typically activates the HPG axis may alter the influence of the adrenal axis on gonadal a xes. In this project, we used male rats and chronic social stimulation that included brief or extended periods with female rats to examine H PA-HPG axes interactions. In experiment 1, we used intact males and a 'chronic social stress' paradigm developed in our previous research th at induces social instability by daily changing the membership of grou p-housed males with females. Thymus weight was reduced and corticoster one levels were marginally increased by chronic social stress, indicat ing a HPA axis hyperactivity. The HPG axis was also activated as shown by the increased weight of the androgen-sensitive sex structures. The se results indicate that when these two axes are stimulated together, neither interferes with nor suppresses activities of the other. Implan ts of corticosterone pellets to adrenalectomized animals that maintain ed constant, high corticosterone levels failed to reverse the gonadal hyperactivity induced by sexual stimulation. In a second experiment, w e studied the influence of different intensity of sexual stimulations on HPA-HPG axes interactions. Increased corticosterone levels and adre nal weight, indicating a HPA hyperactivity, failed to inhibit HPG hype ractivity as measured by the increased sexual organs weight, whatever the sexual intensity of the stimulation. This work demonstrates that t he gonadal axis is freed from suppression when sexual stimulation occu rs together with stress. The general conclusion is that the nature of complex social settings is important in determining interactions betwe en the two neuroendocrine axes. (C) 1997 Elsevier Science Ltd. All rig hts reserved.