Brain serotonin turnover in chronically uremic rats.

Brain serotonin turnover was investigated in chronically uremic and sham-operated pair-fed control rats. Animals were injected ip with 100 mg/kg body wt of pargyline HCl, a nonreversible monoamine oxidase inhibitor, and decapitated 0, 30 and 60 min later. The level of total tryptophan in plasma was decreased, and that of free tryptophan was increased in the uremic group. Uremic and control rats had similar concentrations of tryptophan and serotonin at 0 and 30 min after pargyline administration. However, the brain serotonin concentration was elevated in the uremic group 60 min after pargyline treatment. The brain serotonin turnover rate was higher and serotonin turnover time was lower in the uremic group. These results indicate that uremic stress, in addition to altering plasma tryptophan levels, also affects brain serotonin turnover.