The threshold lowering effects of MDMA (ecstasy) on brain-stimulation reward

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Abstract
3,4-Methylenedioxymethamphetamine (MDMA) is a psychoactive phenylisopropylamine which is structurally similar to both amphetamine-related sympathomimetics and the hallucinogen, mescaline. MDMA produces pleasurable effects which include euphoria, and recent reports continue to demonstrate its widespread recreational use. The aim of the present study was to assess the effects of racemic MDMA on the threshold for rewarding intracranial self-stimulation, an animal model used to assess a drug's abuse liability in man. Rewarding electrical stimulation was delivered via electrodes stereotaxically implanted in the medial forebrain bundle-lateral hypothalamic area of the rat brain. Thresholds were determined by means of a rate-independent psychophysical method. MDMA produced a dose-related lowering of the reward threshold in all four animals tested. Given that increased sensitivity for rewarding brain stimulation, measured as a lowering of the reward threshold, is an animal model of drug-induced euphoria these results suggest a similar mode of action for its reinforcing effects as other abused substances.