Coping with stress: parallelism between the effects of septal lesions on growth hormone and corticosterone levels

In order to characterize the effects of a septal lesion on plasma growth hormone levels, blood samples were taken from normal and sham-operated rats and rats with a bilateral septal lesion under conditions of rest and following stressful stimulation. Nonlesioned control rats evidenced a significant base line diurnal rhythm in plasma growth hormone levels which was unaffected by a septal lesion. In response to stress, plasma growth hormone levels evidenced a significant drop. Minimum levels were reached 15 min after stimulation and remained depressed during 1 hr of observation after stimulation. Rats with a septal lesion evidenced the same pattern of growth hormone response to stressful stimulation as nonlesioned rats, however the magnitude of response was potentiated in septal rats. The present data were compared to the previously published corticosterone data from the same animals. A septal lesion has similar effects on boting 24-hour rhythm of either of these hormones but potentiated the response of both corticosterone and growth hormone to stress even though the direction of response is opposite. The results are interpreted as suggesting the septum is an element in some central coping mechanism which is involved when an organism reacts to environmental demands. Preliminary data further suggest that the same central coping mechanism is involved in both the behavioral and hormonal responses to stress.