Sensitivity of anterior pituitary hormones to graded levels of psychological stress.

The effect of graded levels of stressor intensity on anterior pituitary hormones was studied in adult male rats. Corticosterone, considered as a reflection of ACTH release, and prolactin responses showed a good correlation with the intensity of the stressors. On the contrary, neither LH, GH nor TSH release showed a parallelism with the intensity of the stressors in spite of the fact that they clearly responded to all the stimuli. It appears that the hormones of the anterior pituitary might be divided into two groups: those whose response is sensitive to the levels of emotional arousal elicited by stress, and those displaying a clear but stereotyped response during stress. However, other alternative explanations might exist to justify the present results. The neural mechanisms underlying the two types of response are at present unknown. These data indicate that only the pituitary-adrenal axis and prolactin have some potential utilities as quantitative indices of emotional arousal elicited by currently applied stressors in the rat.