Wheel running alters serotonin (5-HT) transporter, 5-HT1A, 5-HT1B, and alpha1b-adrenergic receptor mRNA in the rat raphe nuclei

Background Altered serotonergic (5-HT) neurotransmission is implicated in the antidepressant and anxiolytic properties of physical activity. In the current study, we investigated whether physical activity alters factors involved in the regulation of central 5-HT neural activity. Methods In situ hybridization was used to quantify levels of 5-HT transporter (5-HTT), 5-HT1A, 5-HT1B, and α1b-adrenergic receptor (α1b ADR) messenger ribonucleic acids (mRNAs) in the dorsal (DRN) and median raphe (MR) nuclei of male Fischer rats after either sedentary housing or 3 days, 3 weeks, or 6 weeks of wheel running. Results Wheel running produced a rapid and lasting reduction of 5-HT1B mRNA in the ventral DRN. Three weeks of wheel running decreased 5-HTT mRNA in the DRN and MR and increased α1b ADR mRNA in the DRN. After 6 weeks of wheel running, 5-HTT mRNA remained reduced, but α1b ADR mRNA returned to sedentary levels. Serotonin1A mRNA was increased in the MR and certain DRN subregions after 6 weeks only. Conclusions Data suggest that the central 5-HT system is sensitive to wheel running in a time-dependent manner. The observed changes in mRNA regulation in a subset of raphe nuclei might contribute to the stress resistance produced by wheel running and the antidepressant and anxiolytic effects of physical activity.