Changes of plasma and adrenal catecholamines and corticosterone in stressed rats with septal lesions.

The effect of septal lesions on plasma catecholamine and corticosterone (B) levels has been studied in rats during single and 7 times repeated immobilization stress (IMO). Blood samples were obtained via a catheter in the tail artery or by decapitation. The increased circulating epinephrine (EPI) and norepinephrine (NE) levels observed in the initial phase of acute stress as well as the elevated baseline EPI level after six times repeated IMO are indicative of an enhanced response of the sympathetic adrenomedullary system after lesions of the septum. After decapitation of rats with septal lesions there was a significant increase in plasma NE one day after the sixth IMO and a block of EPI increase after the seventh IMO compared to sham-operated rats. The adrenocortical system was similarly found to be activated after septal lesions, exhibiting increased baseline plasma B levels. It has been suggested that the septal region affects the studied systems by exerting an inhibitory tonus. The removal of this inhibitory system results in an increase of adrenocortical and sympathetic-adrenomedullary activities.