MDMA (‘Ecstasy’) and methamphetamine combined: Order of administration influences hyperthermic and long-term adverse effects in female rats

Abstract

The acute and long-term dangers of 3,4-methylenedioxymethamphetamine (MDMA, ‘Ecstasy’) and methamphetamine (METH) are well described individually, but their effect in combination is largely unknown. Here groups of female rats were given four MDMA or METH injections within a single session with each injection separated by 2 h. Treatments included MDMA only, METH only, MDMA and METH in a cocktail (MDMA/METH), MDMA (two injections) followed by METH (two injections) (MDMA → METH), or METH followed by MDMA (METH → MDMA). Each injection involved 4 mg/kg of total drug. Drug administration occurred at a high ambient temperature of 28 °C. All treatments produced hyperactivity while the treatments where MDMA was administered first (MDMA, MDMA → METH and MDMA/METH) produced hyperthermia. All treatments involving METH caused significant head weaving. Six weeks after drug treatment all groups showed reduced social interaction relative to controls. MDMA/METH treatment was associated with reduced swimming in the forced swim test. MDMA given alone caused 5-HT depletion in several brain regions while METH given alone caused dopamine depletion in the striatum. The three treatments involving MDMA and METH combinations caused significant depletion of serotonin, dopamine and noradrenaline in several brain regions. Interestingly, the MDMA → METH treatment produced greater hippocampal and cortical 5-HT depletion than the METH → MDMA treatment suggesting an effect of order. These results extend our recent findings of additive toxic effects when METH is combined with MDMA. This has potentially important implications for party drug users who appear to frequently use this combination.