Effect of amphetamines on tryptophan concentrations in mice and rats

Abstract

(±)-Amphetamine and some of its analogues were administered intraperitoneally to mice and rats and the concentrations of tryptophan in tissues were analysed by fluorimetric and microbiologic techniques. The concentration of tryptophan in brain was markedly increased by (±)-amphetamine and reached a maximum about 80 min after drug administration. The effect was dose-dependent with a threshold dose below 1 mg/kg. (+)-Amphetamine was significantly more potent than p-chloroamphetamine and p-hydroxyamphetamine, indicating that the changes in tryptophan concentrations might be related to the central stimulating effect of the drugs. (±)-Amphetamine delayed the disappearance from brain of intravenously administered [3H]tryptophan. Inhibition of monoamine oxidase by nialamide (100 mg/kg) and tryptophan hydroxylase by H 22/54 (500 mg/kg) had no effect on the tryptophan concentration in brain.