Baseline and stress levels of corticosterone, GH, prolactin and MSH were examined in rats with lesions of the septal nuclei. In controls, novel environment produced significant elevations in corticosterone and prolactin, and a drop in GH but no change in MSH levels. In animals with septal ablation, corticosterone elevation was exaggerated, and prolactin and MSH responses were unchanged. GH responses were already maximal so that no potentiation could be detected. Results suggest that neural pathways regulating prolactin and MSH stress responses may differ from those of corticosterone and GH. Administration of PLG, a substance with MIF activity, had no effect on behavioral manifestations of the septal syndrome and direct administration of MSH failed to produce any behaviors that are components of the septal syndrome, suggesting that MSH and PLG are not involved in the syndrome.
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