Serotonin Metabolism and Release in Frontal Cortex of Rats on a Vitamin E‐Deficient Diet

: Rats were fed a control or vitamin E (all‐rac‐α‐tocopheryl acetate)‐deficient diet for 3 or 12 weeks. Serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐HIAA), tryptophan, and α‐tocopherol concentrations were determined in the frontal cortex using HPLC. α‐Tocopherol concentrations fell significantly to 27% of control values at 12 weeks. Tissue 5‐HT, 5‐HIAA, and tryptophan concentrations were not significantly altered by the vitamin E‐deficient diet at either time point. In vivo microdialysis revealed normal basal and K+‐stimulated concentrations of 5‐HT and 5‐HIAA, but extracellular concentrations of tryptophan were significantly decreased after 3 weeks on the vitamin E‐deficient diet, which resulted in an increase in the tissue/extracellular ratio and suggested a change in compartmentation. However, after 12 weeks on the deficient diet these values had returned to normal. Results in general indicate that a prolonged and substantial depletion of brain vitamin E can occur without major disturbance of serotonergic function.