Effect of ambient temperature and a prior neurotoxic dose of 3,4-methylenedioxymethamphetamine (MDMA) on the hyperthermic response of rats to a single or repeated ('binge' ingestion) low dose of MDMA

Rationale. 3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) administration to rats produces acute hyperthermia and long-term neurotoxic damage to 5-hydroxytryptamine (serotonin, 5-HT) neurones. Objective. We wished to examine MDMA-induced hyperthermia in rats housed at normal (19degreesC) and high (30degreesC) room temperatures and investigate the effect of a prior neurotoxic lesion. Methods. Rectal temperature was measured after administration of single or repeated doses of MDMA to rats housed at 19degreesC and 30degreesC. Results. MDMA (5 mg/kg IP) produced a sustained hyperthermic response in rats housed at 30degreesC, but not in rats housed at 19degreesC. A prior (5 weeks earlier) neurotoxic dose of MDMA (12.5 mg/kg IP) resulted in MDMA (5 mg/kg) producing a greater hyperthermic response in rats housed at 30degreesC than in non-pre-treated animals. Repeated MDMA administration (binge dosing; 2, 4 or 6 mg/kg x3) produced dose-dependent hyperthermia in rats housed at 19degreesC, with MDMA (2 mg/kg x3) having little effect. However, this dose produced significant hyperthermia (greater than or equal to2degreesC above control values)in rats housed at 30degreesC following the third dose. A prior neurotoxic dose of MDMA resulted in MDMA (2 mg/kg x3) producing marked hyperthermia (>1degreesC) after the first dose and severe hyperthermia (greater than or equal to2degreesC) after the third dose. Conclusions. MDMA administration to rats housed at 30degreesC produces a more severe hyperthermic response than that seen in rats housed at 19degreesC. A prior neurotoxic dose enhances the response further in animals housed at 30degreesC. Binge dosing produces a higher final peak response than a similar non-divided dose. This effect is more marked in animals housed at high room temperature. These data may have implications for recreational users of MDMA in hot environments, particularly those who may have damaged serotoninergic neurones because of prior heavy or frequent use of the drug.