"Designer" amphetamines: effects on behavior and monoamines with or without reserpine and/or alpha-methyl-para-tyrosine pretreatment

Abstract

Rats were given single injections of vehicle or one of three doses of (+)-amphetamine (AM), 4-methoxyamphetamine (MA) or 4-ethoxyamphetamine (EA) after pretreatment with vehicle or reserpine, and vehicle or alpha-methyl-para-tyrosine (AMPT). EA is a "designer" drug that was recently seized from an illicit laboratory in Canada. Locomotion of the rats was recorded after treatment with the drugs, and whole brain levels of the drugs as well as monoamine neurotransmitters and their major acidic metabolites were then determined. Neither of the ring-substituted AM analogues influenced locomotion. AM induced locomotion in a dose-dependent manner, and this effect was blocked by AMPT but potentiated by reserpine. Brain concentrations of EA were lower than those of the other two drugs. The brain levels of monoamines and their metabolites indicate that AM releases a newly synthesized pool of dopamine which is transferred to vesicles after re-uptake. A very low dose of AM, but not higher doses, was found to elevate serotonin (5-hydroxytryptamine: 5-HT) levels independently of effects on catecholamines. Both MA and EA affected monoamine metabolites in a manner consistent with actions as reversible inhibitors of monoamine oxidase-an effect which has been previously demonstrated to be true for MA. Both drugs increased 5-HT levels at a very low dose, as did AM, but also increased noradrenaline levels at this dose. It is concluded that EA is not a psychomotor stimulant, but is similar in many of its effects to MA, a potent hallucinogen.