The action of single and repeated doses of p-bromo-methamphetamine on the monoamine content and turnover rate in rat brain

Abstract

The effect of p-bromo-methamphetamine ( pBrMA) on serotonergic and catecholaminergic neurones in the rat brain was studied. Acute (15 mg/kg, s.c.) and chronic (30 × 15 mg/kg, s.c.) administration of the drug caused a long-lasting decrease in serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) content of whole brain. In contrast the catecholamine (CA) levels remained unchanged. Detailed studies of the 5-HT and CA content of brain regions showed a time-dependent decrease in 5-HT after acute injection, and a marked and persistent reduction in 5-HT and 5-HIAA after chronic treatment. In both injection regimens the content of noradrenaline (NA) was enhanced in the cortex. The turnover rate of 5-HT, dopamine (DA) and NA was reduced after acute treatment. Repeated injections caused a decrease in 5-HT turnover, while that of NA remained unchanged. However, the turnover rate of DA was enhanced. The present data appears to confirm the previous suggestion that after chronic treatment, when the rats show improvement in their learning performances, the serotonergic tone of the brain is decreased while dopaminergic tone is increased.