Rapid accumulation of H3-serotonin in brains of rats receiving intraperitoneal H3-tryptophan: Effects of 5, 6-dihydroxytryptamine or female sex hormones

Summary The specific activities of brain and plasma H³-tryptophan and brain H³-serotonin increased approximately linearly for only 6 min after animals received intraperitoneal tracer doses of H³-tryptophan. The maximum rate of brain serotonin synthesis could thus be estimated from data collected during this interval, but not thereafter. Pretreatment of rats with intraventricular 5, 6-dihydroxytryptamine, a compound that damages serotoninergic neurons, decreases brain tryptophan and serotonin concentrations, accelerates the labelling of brain tryptophan by injected H³-tryptophan, and markedly decreases the rate at which H³-tryptophan accumulates as brain H³-serotonin. The treatment of oophorectomized rats with estradiol and progesterone does not appear to modify brain serotonin synthesis.