Motor Activity Increases Tryptophan, 5‐Hydroxyindoleacetic Acid, and Homovanillic Acid in Ventricular Cerebrospinal Fluid of the Conscious Rat

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Abstract
An investigation was made into the effect of running (1 h at 20 m/min) on central serotonergic and dopaminergic metabolism in trained rats. Methodology involved continuous withdrawal of cerebronspinal fluid (CSF) from the third ventricle of conscious rats and measurements of tryptophan (TRP), 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) levels during a 2 h post-exercise period. All three compounds were increased during the four following exercises and returned to their basal values within an hour later. CSF flow rate was stable when metabolite levels were elevated. Brain determinations indicated that CSF metabolite variations only qualitatively paralleled brain changes. Indeed, post-exercise TRP, 5-HIAA, and HVA levels were increased to a greater extent in brain when compared to CSF. It is suggested that increased serotonergic and dopaminergic metabolism, caused by motor activity, may be involved in the behavioral effects of exercise.