Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal responses to chronic cold stress in rats

Animals prenatally exposed to ethanol typically exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness to stressors. In contrast to previous studies that have investigated effects of prenatal ethanol exposure on HPA responses to acute or intermittent stressors, our study investigated HPA responses to a chronic continuous stressor, cold stress (4 degrees C for 0, 1, or 3 days). We tested the hypothesis that prenatal ethanol exposure would result in increased plasma corticosterone (CORT) and adrenocorticotropin (ACTH) responses and increased peptide [corticotropin-releasing factor and vasopressin] mRNA levels in the paraventricular nucleus (PVN) of the hypothalamus compared to that in control animals. In addition, CORT and ACTH responses were measured after exposure to an acute stressor (i.p. isotonic saline injection), superimposed during chronic cold exposure, to examine possible sensitization of the HPA response to the acute stress. Thus, blood samples were collected at the end of each of the three periods of cold exposure, either before (0 min) or 15 min after acute stress. The subjects were adult male and female Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups. Exposure to cold stress resulted in significant body weight loss in E males at 1 day and in both males and females of all prenatal treatment groups by 3 days of cold stress. Males in all prenatal groups also exhibited significant increases in adrenal weight:body weight ratios. Cold stress alone (0 min condition) increased CORT levels in E males and overall ACTH levels in E males and females compared to controls. ACTH levels were also higher overall in E compared to control males after acute stress (15 min condition). Sensitization of the CORT response to acute stress was observed in males but not females across all prenatal treatment groups. Corticotropin-releasing factor and vasopressin mRNA levels in the PVN were not significantly affected by prenatal treatment or chronic cold stress in either males or females. In contrast, both males and females displayed increases in PVN thyrotropin-releasing hormone (TRH) mRNA levels after cold stress. These data support and extend previous work demonstrating differential effects of prenatal ethanol exposure on HPA responsiveness of male and female offspring, and suggest that E males may be more vulnerable to the effects of chronic cold stress than E females.