Comparative Effects of Substituted Amphetamines (PMA, MDMA, and METH) on Monoamines in Rat Caudate

Paramethoxyamphetamine (PMA), a drug sold illicitly as 'ecstasy' and linked to fatalities in Australia and the United States, produces neurotoxic effects on dopamine and serotonin systems in rats similar to MDMA and methamphetamine (METH). Extracellular levels of dopamine, its metabolites DOPAC and HVA, serotonin (5-HT), and its metabolite 5-HIAA were measured in the caudate of freely moving rats via microdialysis. METH (2.5 mg/kg) increased dopamine 700% and decreased DOPAC 30% and HVA 50%, with no serotonin changes. MDMA (10 and 20 mg/kg) increased dopamine up to 950% and serotonin up to 575%.

Study at a glance

Abstract

A bstract : Paramethoxyamphetamine (PMA) is a methoxylated phenethylamine derivative that has been used illicitly in Australia since 1994. PMA is also becoming popular at rave parties in the United States. PMA raised concern when a series of fatalities resulted after its use in South Australia, where it was marketed as “ecstasy,” which is the colloquial name for MDMA. In the present study, we evaluated the comparative neurotoxicity of substituted amphetamines in rats. Extracellular levels of dopamine (DA), 3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5‐HT), and 5‐hydroxyindoleacetic acid (5‐HIAA) were assayed in the caudate of freely moving rats using microdialysis and HPLC‐EC. Dialysates were assayed every 20 minutes for 4 hours after an intraperitoneal (i.p.) injection of PMA (2.5, 5, 10, 20 mg/kg), MDMA (10 and 20 mg/kg), or METH (2.5 mg/kg). METH produced a significant increase in extracellular DA (700%), and significant decreases in extracellular DOPAC and HVA (30% and 50%), with no detectable changes in either 5‐HT or 5‐HIAA. MDMA produced significant increases in DA (700% at 10 mg/kg and 950% at 20 mg/kg) and decreases in DOPAC (15% for both 10 and 20 mg/kg), and HVA (50% at 10 mg/kg and 35% at 20 mg/kg). MDMA also increased 5‐HT (350% at 10, and 575% at 20 mg/kg), and decreased 5‐HIAA to 60% for both dose levels. PMA produced no detectable increases in DA at dose levels of 2.5, 5, or 10 mg/kg, but significantly increased DA (975%) at a dose of 20 mg/kg. However, PMA significantly decreased DOPAC at all dose levels (75% at 2.5; 40% at 5; 30% at 10; 10% at 20 mg/kg), with comparable decreases in HVA at all dose levels. PMA also produced significant increases in 5‐HT at 10 and 20 mg/kg (350% for both dose levels), with no detectable changes in 5‐HT at 2.5 or 5 mg/kg. All dose levels of PMA significantly decreased 5‐HIAA (50 to 70%). These data suggest that PMA, like MDMA and METH, is capable of producing dopaminergic and serotonergic neurotoxicity.