Some neurochemical effects of amphetamine, methylamphetamine and p‐bromomethylamphetamine in the rat

Abstract

1 Low doses of d-amphetamine increased brain noradrenaline concentrations in the rat; doses greater than 5 mg/kg, however, caused a decrease. Methylamphetamine also showed this dual effect, but a reduction in brain noradrenaline concentration only occurred when doses greater than 10 mg/kg were administered. p-Bromomethylamphetamine did not significantly reduce brain noradrenaline concentrations even at a dose of 60 mg/kg. The order of potency in reducing the concentration of noradrenaline correlated with the central stimulant effects; d-amphetamine produced the greatest and p-bromomethylamphetamine the least increase in motor activity. 2 d-Amphetamine and d-methylamphetamine potentiated the action of 4,α-dimethyl-m-tyramine (H77/77) in depleting brain noradrenaline; the greatest potentiation was produced by d-amphetamine. This suggests that the phenylethylamines may affect brain noradrenaline concentrations by acting on the reserpine resistant uptake mechanism. 3 Differences were found in the effect of the three drugs on brain dopamine concentrations; d-amphetamine caused a decrease while p-bromomethylamphetamine caused an increase. Methylamphetamine had no effect on the concentration of dopamine. Only p-bromomethylamphetamine significantly reduced the depletion of brain dopamine concentrations caused by H77/77. 4 Methylamphetamine and p-bromomethylamphetamine reduced the concentration of 5-hydroxytryptamine (5-HT) in the brain; administration of the same dose of d-amphetamine did not change the concentration of 5-HT. 5 Changes in the blood and brain concentrations of tyrosine and tryptophan, and in the concentration of γ-amino-n-butyric acid in the brain could not be correlated with the changes observed in the concentrations of biogenic amines in the brain.