Figure 4.

Plasma corticosterone (mean ± SEM) reflects anxiogenic conditions. A) In the absence of social interaction in the SAM, icv injection (vehicle, hatched bars) significantly elevated corticosterone concentrations, which is reduced somewhat by NPS icv injection (cross hatched bars). B) During social aggressive interactions in the SAM, corticosterone concentrations are elevated; highest in submissive animals (cross hatched bars), and significantly reduced in those that escape (left hatching) compared with controls (open bar). Social stress-induced elevation of corticosterone secretion is ameliorated by access to voluntary exercise on a running wheel for submissive animals (*, gray cross hatched bar) and also for escaping mice (#, gray left hatched bar); while presence of the running wheel in the absence of social interaction did not affect plasma corticosterone concentrations. Bars marked with differing letters above the mean/error bar (e.g. A, B, C; or X and Y) are significantly different, whereas bars marked with the same letter (such as X) are not significantly different. Bars marked # reflect significant differences between escaping animals without access to running wheels and escaping animals with running wheels (Otherwise bars marked A, B, or C, are not compared with bars labeled X, Y, or Z); and * designates significant reduction in corticosterone in submissive animals with running wheels compared to submissive animals without access.