[ACTH, corticosterone and beta-endorphin in the blood plasma of rats under prolonged immobilization stress].

Radioimmunoassays were employed to study variation in the concentration of corticosterone, ACTH and beta-endorphin in rat blood plasma at different times of the 30-hour immobilization and under the effect of a short-term action of ecologically significant negative stimulation emanating from other animals. Both prolonged immobilization stress and short-term emotional reaction produced appreciable alterations in the blood plasma content of all the hormones under study. The findings indicate that variations in the corticosterone and beta-endorphin levels were in the best agreement.