Effects of Swimming Exercise on Circadian Sleep-waking Rhythms and Brain Serotonin Metabolism in Rats

Abstract

Polygraphic recordings of circadian sleep-waking rhythms of rats “were made before and after swimming exercise which was loaded to the animals in the dark period. By visual inspection of the recordings, an exercise-induced increase in the amount of slow-wave sleep (SWS) was observed in the next dark period. In the dark period, 15 hours after the swimming, tryptophan (TRP), serotonin and 5-hydroxyindoleacetic acid (5-HIAA) in several regions of rat brain were measured to clarify the mechanisms of the exercise-induced increase in SWS. The concentrations of TRP and 5-HIAA in the midbrain of the exercised rats were significantly higher than in the control ones. The cortical level of 5-HIAA was also high in the exercise group. The serotonin levels in both the brain regions of the exercised rats were nearly the same with the control. From these results, it is inferred that the increased amount of SWS after the swimming exercise might be attributable to enhanced activity of serotonergic neurons in the midbrain and the cerebral cortex. © 1984, National Institute of Occupational Safety and Health. All rights reserved.