Reduced Adrenal Activation in a Rat Line Selected for High Alcohol Sensitivity

Abstract

Background A rat line developed by selective breeding for high alcohol sensitivity has blunted corticosterone responses to alcohol and stress. In the present study, we determined possible differences in adrenal activation after alcohol and motor performance testing between the alcohol-sensitive alcohol-nontolerant and alcohol-insensitive alcohol-tolerant rats. Methods The animals received ethanol (2 g/kg, intraperitoneally), and 30 min later they were subjected to a motor function test (i.e., normal selection test used in the breeding of the lines); the control animals for both rat lines received no treatment and minimal handling. Blood corticosterone and ACTH levels at the single time point were determined by radioimmunoassay, and adrenal activation was determined by in situ hybridization of the immediate early gene c-fos, nor1, nurr1, and NGFI-B mRNA expression. Results The alcohol nontolerant rats had lower corticosterone but normal ACTH levels after ethanol and motor testing. Adrenal early gene expression of all of the genes studied was strongly induced by the treatment in both rat lines, but the inductions of c-fos, nor1, and nurr1 were significantly lower in the alcohol-sensitive animals. Acute treatment with a high dose of ACTH also induced less adrenal gene expression in the alcohol-sensitive animals. Conclusions The results suggest that the reduced adrenal activation is associated with high alcohol sensitivity in a genetic animal model, which is in agreement with the human findings of alcohol insensitivity during glucocorticoid treatment.