title: Preexposure to MDMA ("Ecstasy") delays acquisition but facilitates MDMA-induced reinstatement of amphetamine self-administration behavior in rats.
abstract: The current experiment investigated the effect of 3,4-methylenedioxymethamphetamine (MDMA; 'Ecstasy') preexposure on the acquisition of intravenous amphetamine self-administration and the reinstatement of amphetamine-seeking behavior by either MDMA or amphetamine. Rats were preexposed to a 5-HT depleting regime of MDMA (5 mg/kg every hour for 4 h on two consecutive days) or equivalent vehicle injections. Intravenous self-administration of low dose d-amphetamine (0.03 mg/kg/infusion) on a FR1 schedule was subsequently assessed. The rats were then given 2 weeks of extinction and tested for drug-seeking behavior with priming doses of amphetamine or MDMA. Brains were analysed for monoamine content using high-performance liquid chromatography (HPLC). MDMA-preexposed rats were initially slower to acquire amphetamine self-administration. However, by day 6 of acquisition, there was no difference from controls. Following extinction, amphetamine (1 mg/kg, i.p.) reinstated drug seeking and produced locomotor hyperactivity in both MDMA- and vehicle-pretreated animals. However, MDMA (5 mg/kg, i.p.) was only effective in producing amphetamine seeking and hyperactivity in MDMA-pretreated rats. MDMA pretreatment caused significant decreases in 5-hydroxy-indolacetic acid (5-HIAA) and 5-HT in several brain regions. These results suggest that 5-HT depletion induced by MDMA may initially slow the acquisition of amphetamine self-administration but that MDMA preexposure may also sensitize animals to the locomotor stimulating and priming effects of MDMA on drug-seeking behavior.
authors.affiliation: School of Psychology, University of Sydney, NSW 2006, Australia.
authors.forename: Kirsten C
authors.initials: KC
authors.lastname: Morley
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Cornish
authors.forename: Kong M
authors.initials: KM
authors.lastname: Li
authors.forename: Iain S
authors.initials: IS
authors.lastname: McGregor
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D003913:Dextroamphetamine / Q000008:administration & dosage*; D004347:Drug Interactions; D005108:Extinction, Psychological / Q000187:drug effects; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000008:administration & dosage* / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D012646:Self Administration; D012701:Serotonin / Q000378:metabolism; D018490:Serotonin Agents / Q000008:administration & dosage; D019966:Substance-Related Disorders / Q000209:etiology
chemical_list: D018490:Serotonin Agents; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D003913:Dextroamphetamine