Prepulse inhibition and habituation of acoustic startle response in male MDMA ('ecstasy') users, cannabis users, and healthy controls.

Chronic administration of 3,4-methylenedioxymethamphetamine (MDMA) is associated with long-term depletion of serotonin (5-HT) and loss of 5-HT axons in the brains of rodents and nonhuman primates. Despite the broad database concerning the selective serotonergic neurotoxicity of recreational MDMA consumption by humans, controversy still exists with respect to the question of whether the well-known functional consequences of these neurotoxic effects, such as memory impairment, were caused by chronic 5-HT deficiency. Habituation and prepulse inhibition (PPI) of the acoustic startle response (ASR) can be used as a marker of central serotonergic functioning in rodents and humans. Thus, we investigated the functional status of the central serotonergic system in chronic but abstinent MDMA users by measuring PPI and habituation of ASR. PPI and habituation of ASR were measured in three groups. The first group (MDMA group) included 20 male drug-free chronic users of MDMA; the second group (cannabis group) consisted of 20 male drug-free chronic users of cannabis; and the third group (healthy controls) comprised 20 male participants with no history of illicit drug use. Analysis revealed significantly increased PPI of MDMA users compared to those of cannabis users and healthy controls. Cannabis users and healthy controls showed comparable patterns of PPI. There were no differences in habituation among the three groups. These results suggest that the functional consequences of chronic MDMA use may be explained by 5-HT receptor changes rather than by a chronic 5-HT deficiency condition. Use of cannabis does not lead to alterations of amplitude, habituation, or PPI of ASR.