Induction of c-fos in nucleus accumbens in naive male Balb/c mice after wheel running.

Immunocytochemical labeling of the transcription factor c-Fos was used to determine whether wheel running (WR) activates nucleus accumbens (NAcc) neurons in naive male Balb/c mice. The results indicate compared to novel environment exploration and forced locomotor activity, WR increases c-Fos labeling in the middle level of the core but not the shell of the NAcc. These data show that WR activates middle-core NAcc neurons more effectively than other locomotor activities. The middle core of the NAcc may be a critical region for the self-reinforcing properties of WR.