The role of the hypothalamic-pituitary-adrenocortical axis in post-stress induced ethanol consumption by rats

1. Previous studies conducted in our laboratory demonstrated that rats given a choice between a 0.1% saccharin solution or 10% ethanol/0.1% saccharin solution and repeatedly exposed on an unpredictable basis to stressful stimuli, consumed increasing quantities of the ethanol solution following cessation of stressor presentation as compared to nonstressed control rats. 2. Stressful stimuli potently activate the hypothalamic-pituitary-adrenocortical (HPA) axis, thus a systematic investigation of the HPA axis and its involvement in post-stress induced ethanol consummatory behavior was undertaken. 3. Exposure to repetitive unpredictable stressful stimuli did not induce the free-choice consumption of ethanol in either hypophysectomized rats or chronic dexamethasone treated rats. 4. Adrenalectomized rats exposed to chronic unpredictable stressful stimuli consumed increased quantities of ethanol following cessation of stressful stimuli in both a quantitative and qualitative manner which mirrored that of intact animals. 5. Repeated intravenous administration of exogenous adrenocorticotropin (ACTH1-39) on an unpredictable basis also induced ethanol consuming behavior, following the discontinuation of its administration. 6. These results suggest that elimination of the pituitary or pharmacological antagonism of stress-induced HPA activation will prevent post-stress induced ethanol consummatory behavior. 7. Conversely, activation of a functional hypothalamic-pituitary system or repeated administration of exogenous ACTH1-39 will initiate ethanol consumption in rats. 8. Thus, hormones secreted from the pituitary, namely ACTH, appear to play a crucial role in the post-stress induced initiation of ethanol consuming behavior in rats.