HPA Axis Activation by Ethanol Dependence in Adult and Adolescent Rats

Alcoholism is a disorder marked by cycles of heavy drinking and chronic relapse, and adolescents are an age cohort particularly susceptible to consuming large amounts of alcohol, placing them at high risk for developing an alcohol use disorder. Adolescent humans and rats voluntarily consume more alcohol than their adult counterparts, suggesting that younger consumers of alcohol may be less sensitive to its aversive effects, which are regulated by the function of the hypothalamic-pituitary-adrenal (HPA) stress axis. While HPA axis dysfunction resulting from ethanol exposure has been extensively studied in adult animals, what happens in the adolescent brain remains largely unclear. In this study, chronic injections of ethanol was used to model alcohol dependence in adult and adolescent rats, and post-withdrawal anxiety behaviors were measured using light-dark box testing. Furthermore, corticosterone (CORT) release during treatment and after withdrawal was measured by collecting fecal and plasma samples from adults and adolescents. It was found that adults, but not adolescents, exhibit significant anxiety-like behavior following chronic ethanol withdrawal. Additionally, while the process of chronic ethanol treatment elicits an increase in day-by-day CORT release in both adults and adolescents, significantly sustained levels of CORT were not observed during withdrawal for either age group. Moreover, it was found that adults experience a longer-lasting CORT increase during chronic treatment, suggesting a larger and more robust period of dysfunction in the HPA axis for older consumers of alcohol. These results highlight CORT and glucocorticoids in general as a potential therapeutic target for treatment for alcoholism, especially that which has an onset during adolescence.

Changes to the North Atlantic subtropical high and its role in the intensification of summer rainfall variability in the southeastern United States

This study investigates the changes of the North Atlantic subtropical high (NASH) and its impact on summer precipitation over the southeastern (SE) United States using the 850-hPa geopotential height field in the National Centers forEnvironmental Prediction (NCEP) reanalysis, the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), long-term rainfall data, and Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) model simulations during the past six decades (1948-2007). The results show that the NASH in the last 30 yr has become more intense, and its western ridge has displaced westward with an enhanced meridional movement compared to the previous 30 yr. When the NASH moved closer to the continental United States in the three most recent decades, the effect of the NASH on the interannual variation of SE U.S. precipitation is enhanced through the ridge's north-south movement. The study's attribution analysis suggested that the changes of the NASH are mainly due to anthropogenic warming. In the twenty-first century with an increase of the atmospheric CO2 concentration, the center of the NASH would be intensified and the western ridge of the NASH would shift farther westward. These changes would increase the likelihood of both strong anomalously wet and dry summers over the SEUnited States in the future, as suggested by the IPCC AR4 models. © 2011 American Meteorological Society.