5-HT2C Receptors in the Basolateral Amygdala and Dorsal Striatum Are a Novel Target for the Anxiolytic and Antidepressant Effects of Exercise

Physical activity reduces the incidence and severity of psychiatric disorders such as anxiety and depression. Similarly, voluntary wheel running produces anxiolytic- and antidepressant-like effects in rodent models. The specific neurobiological mechanisms underlying the beneficial properties of exercise, however, remain unclear. One relevant pharmacological target in the treatment of psychiatric disorders is the 5-HT_2C receptor (5-HT_2CR). Consistent with data demonstrating the anxiogenic consequences of 5-HT_2CR activation in humans and rodents, we have previously reported that site-specific administration of the selective 5-HT_2CR agonist CP-809101 in the lateral/basolateral amygdala (BLA) increases shock-elicited fear while administration of CP-809101 in the dorsal striatum (DS) interferes with shuttle box escape learning. These findings suggest that activation of 5-HT_2CR in discrete brain regions contributes to specific anxiety- and depression-like behaviors and may indicate potential brain sites involved in the anxiolytic and antidepressant effects of exercise. The current studies tested the hypothesis that voluntary wheel running reduces the behavioral consequences of 5-HT_2CR activation in the BLA and DS, specifically enhanced shock-elicited fear and interference with shuttle box escape learning. After 6 weeks of voluntary wheel running or sedentary conditions, the selective 5-HT_2CR agonist CP-809101 was microinjected into either the BLA or the DS of adult Fischer 344 rats, and shock-elicited fear and shuttle box escape learning was assessed. Additionally, in-situ hybridization was used to determine if 6 weeks of voluntary exercise changed levels of 5-HT_2CR mRNA. We found that voluntary wheel running reduced the behavioral effects of CP-809101 and reduced levels of 5-HT_2CR mRNA in both the BLA and the DS. The current data indicate that expression of 5-HT_2CR mRNA in discrete brain sites is sensitive to physical activity status of the organism, and implicates the 5-HT_2CR as a target for the beneficial effects of physical activity on mental health.