The Effect of Exercise on Anxiety- and Depression-Like Behavior of Aged Rats

Abstract

We investigated the effects of exercise in multiple sessions on anxiety- and depression-like behavior during aging, and the role of serotonin and serotonin 1A receptors in this process. Both 24-month-old (aged) and 6-month-old (adult) female rats were divided into five groups; aged control, adult control, aged + serotonin re-uptake inhibitors (SSRIs), aged + exercise, and aged + SSRIs + exercise. After exercise, all groups were evaluated using the open field arena, elevated plus maze and forced swim tests. We assessed serum corticosterone levels; number of amygdala, hippocampus and prefrontal cortex cells; tissue serotonin and serotonin 1A (5-HT1A) levels. In the open field test, aged rats exhibited a significant increase in locomotor activity compared to the SSRIs and SSRIs + exercise groups. During the elevated plus maze test, aged rats were observed less frequently in the open arms of assembly compared to adults. The duration increased in the exercise group and remained unchanged in the SSRIs group. In the forced swim test, the aged rats were more immobile compared to adults; no change was observed in the immobility time between these groups. The tissue serotonin levels in amygdala and hippocampus were higher in SSRIs + exercise group compared to the aged, exercised and SSRIs groups. The number of cells in the hippocampus, prefrontal cortex and amygdala decreased in the aged group compared to adult rats; increased numbers of cell were observed in exercise, SSRIs and SSRIs + exercise groups compared to aged rats. Exercise in multiple sessions may increase the number of cells in the hippocampus, prefrontal cortex and amygdala, which may reduce senile anxiety and depression. Also, serotonin and serotonin 1A receptors may play role in depression-like behavior.