Wheel running alters serotonin (5-HT) transporter, 5-HT1A, 5-HT1B, and alphal1b-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 alpha(1b)-adrenergic receptor (alpha(1b)ADR) messenger ribonucleic acids (mRNAs) in the dorsal (DRN) and median raphe (MR) nuclei of mate 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 alpha(1b)ADR mRNA in the DRN. After 6 weeks of wheel running, 5-HTT mRNA remained reduced, but alpha(1b)ADR mRNA returned to sedentary levels. Serotonin(1A) 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.