Researchers administered saline or 10 mg/kg MDMA to C57B1/6 mice in order to investigate the effects of MDMA on gene expression in mouse frontal cortex and midbrain, with gene expression assessed via differential display polymerase chain reaction (DD-PCR). The researchers also performed immunoassays in normal ("wild-type") and serotonin transporter knockout (SERT KO) mice. After finding increased expression of GABA transporter genes, they next assessed effects of GABAergic drugs on MDMA-associated lethality and neurotoxicity. Mice in most studies were killed 2 h post-drug, except during a time-course study, wherein mice were killed 2 h, 2 d or 7 d post-drug, and in the investigation of GABAergic involvement in MDMA lethality, wherein mice were monitored for 10 days. DD-PCR detected changes in expression of 11 genes 2 h after MDMA. Four of 11 genes were 98% identical to previously cloned genes, and 2 genes were apparently not identified before. MDMA increased expression in 5 of 11 genes, and decreased expression the remaining 6 genes. Increased expression was seen in mouse GABA-transporter-1 (mGAT1) gene activity in frontal and midbrain areas. MDMA increased activity in the mGAT4 gene in frontal and midbrain areas. Real-time PCR analysis determined that MDMA did not alter activity in mGAT2 and MGAT3 GABA transporter genes. MDMA increased MGAT1 gene expression for up to 7 days post-drug, but mGAT4 expression declined during or after 2 days post-drug, with frontal MGAT4 expression almost comparable to controls at 7 d post-drug, and midbrain expression completely restored to control levels at 7 d post-drug. Western blot immunoassay with anti-GAT1 antibodies found 2.1 to 2.4 times greater GABA transporter (GAT) immunoreactivity (indicative of increased expression) in frontal and midbrain areas in "wild-type," but not in SERT-KO mice, implying an association between serotonin release and increased GAT gene expression. Mice received 20 to 200 mg tiagabine (GAT inhibitor), NO-711 (GAT inhibitor), vigabatrin (GABAergic agonist, inhibits steps in GABA metabolism), guvacine (GAT inhibitor, poorly crosses blood-brain barrier) or valproate (anticonvulsant and mood stabilizer, action unknown, presumably not GABAergic) 15 min before receiving 65 mg/kg MDMA. (This dose of MDMA is usually lethal in mice). Tiagabine completely and dose-dependently protected mice from MDMA lethality, and NO-711 was partially protective (protection only lasted up to 24 h post-drug), with effects also dose-dependent. Greater survival did not occur after valproate, guvacine or vigabatrin pre-administration. However the authors did not report whether tiagabine or NO-711 affected MDMA-induced hyperthermia, so these drugs may also have reduced lethality by reducing hyperthermia. Taken together, study findings imply that MDMA reduces GABA transport, probably indirectly through serotonin release or action on serotonin receptors, and that reduced extracellular GABA may have a role in altering thermoregulation. It is important to note another study of gene expression in rats given 20 mg/kg MDMA (Thiriet et al. 2002) did not report detecting changes in GAT gene activity, suggesting a potential dose-related or inter-species difference in MDMA effects on GABA gene expression. Given these differences, it is difficult to extrapolate study findings to other species, including humans.