Electrophysiologic changes in ventral midbrain dopaminergic neurons resulting from (+/-) -3,4-methylenedioxymethamphetamine (MDMA-"Ecstasy")

3,4-Methylenedioxymethamphetamine (MDMA) Alters Synaptic Dopamine Release in the Dorsal Striatum Through Nicotinic Receptors and DAT Inhibition

An increase of extracellular dopamine (DA) has been implicated in the psychostimulant properties of 3,4-methylenedioxymethamphetamine (MDMA). Although this drug has been reported to affect the DA uptake transporter (DAT), it might activate other mechanisms to regulate the outflow of DA in the brain. Our aim was to examine the overall effects of MDMA on the release of DA in the striatum. We studied the effect of MDMA on stimulus-evoked synaptic DA release in dorsal striatal slices of mice using in vitro amperometric techniques. We also tested the effects of MDMA on the nicotine-induced responses in substantia nigra pars compacta (SNpc) neurons using intracellular electrophysiological recordings. MDMA (1-30 µM) depressed the amplitude and prolonged the decay-time of synaptic DA release in the striatum. Interestingly, in the presence of the broad nicotinic receptor antagonist mecamylamine, and the more selective α₄β₂ antagonist dihydroβerythroidine (DHβE), MDMA enhanced both peak and duration of DA release. A similar effect was found on cocaine-insensitive (DAT-CI) mice slices. Concentrations of MDMA higher than 100 µM enhanced striatal DA outflow that was in turn, reduced by cocaine. Electrophysiological recordings of dopaminergic neurons in SNpc showed that MDMA depressed the effects of nicotine. Our data are consistent with a prevalent MDMA-induced inhibition of the synaptic release of DA in the dorsal striatum mediated by an interaction with nicotinic receptors. This drug also blocks DAT acting on a different site from cocaine and, at higher concentrations, has amphetamine-like releasing properties.

Looking for prosocial genes: ITRAQ analysis of proteins involved in MDMA-induced sociability in mice

Social behavior plays a fundamental role in life of many animal species, allowing the interaction between individuals and sharing of experiences, needs, and goals across them. In humans, some neuropsychiatric diseases, including anxiety, posttraumatic stress disorder and autism spectrum disorders, are often characterized by impaired sociability. Here we report that N-Methyl-3,4-methylenedioxyamphetamine (MDMA, "Ecstasy") at low dose (3mg/kg) has differential effects on mouse social behavior. In some animals, MDMA promotes sociability without hyperlocomotion, whereas in other mice it elevates locomotor activity without affecting sociability. Both WAY-100635, a selective antagonist of 5-HT1A receptor, and L-368899, a selective oxytocin receptor antagonist, abolish prosocial effects of MDMA. Differential quantitative analysis of brain proteome by isobaric tag for relative and absolute quantification technology (iTRAQ) revealed 21 specific proteins that were highly correlated with sociability, and allowed to distinguish between entactogenic prosocial and hyperlocomotor effects of MDMA on proteome level. Our data suggest particular relevance of neurotransmission mediated by GABA B receptor, as well as proteins involved in energy maintenance for MDMA-induced sociability. Functional association network for differentially expressed proteins in cerebral cortex, hippocampus and amygdala were identified. These results provide new information for understanding the neurobiological substrate of sociability and may help to discover new therapeutic approaches to modulate social behavior in patients suffering from social fear and low sociability.

Role of serotonin via 5-HT2B receptors in the reinforcing effects of MDMA in mice

The amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) reverses dopamine and serotonin transporters to produce efflux of dopamine and serotonin, respectively, in regions of the brain that have been implicated in reward. However, the role of serotonin/dopamine interactions in the behavioral effects of MDMA remains unclear. We previously showed that MDMA-induced locomotion, serotonin and dopamine release are 5-HT_2B receptor-dependent. The aim of the present study was to determine the contribution of serotonin and 5-HT_2B receptors to the reinforcing properties of MDMA.

We show here that 5-HT_2B^−/− mice do not exhibit behavioral sensitization or conditioned place preference following MDMA (10 mg/kg) injections. In addition, MDMA-induced reinstatement of conditioned place preference after extinction and locomotor sensitization development are each abolished by a 5-HT_2B receptor antagonist (RS127445) in wild type mice. Accordingly, MDMA-induced dopamine D1 receptor-dependent phosphorylation of extracellular regulated kinase in nucleus accumbens is abolished in mice lacking functional 5-HT_2B receptors. Nevertheless, high doses (30 mg/kg) of MDMA induce dopamine-dependent but serotonin and 5-HT_2B receptor-independent behavioral effects.

These results underpin the importance of 5-HT_2B receptors in the reinforcing properties of MDMA and illustrate the importance of dose-dependent effects of MDMA on serotonin/dopamine interactions.

Changes in leptin, ghrelin, growth hormone and neuropeptide-Y after an acute model of MDMA and methamphetamine exposure in rats

Club drug abuse is a growing problem in the United States. Beyond addiction and toxicity are endocrine effects which are not well characterized. Specifically, the changes in appetite following exposure to drugs of abuse are an interesting but poorly understood phenomenon. Serum hormones such as leptin, ghrelin, growth hormone (GH), and neuropeptide-Y (NP-Y) are known to affect appetite, but have not been studied extensively with drugs of abuse. In this work, we examine the effects of club drugs 3,4-methylenedioxymethamphetamine (MDMA) (ecstasy) and methamphetamine (METH) (doses of 5, 20 and 40 mg/kg) on serum concentrations of these hormones in adult male Sprague-Dawley rats 6, 12, 24 and 48 hours after drug administration. In a dose-dependent manner, MDMA was shown to cause transient significant decreases in serum leptin and GH followed by a base line recovery after 24 hours. Conversely, serum ghrelin increased and normalized after 24 hours. Interestingly, serum NP-Y showed a steady decrease in both treatment of MDMA and METH at different time points and dosages. In humans, abuse of these drugs reduces eating. As evident from these data, acute administration of METH and MDMA had significant effects on different serum hormone levels involved in appetite regulation. Future studies should be performed to see how chronic, low dose drug administration would affect hormone levels and try to answer questions about the physiological mechanisms involved in the anorexic paradigm observed in drug use.