Acute MDMA administration alters the distribution and circadian rhythm of wheel running activity in the rat.

Ecstasy users report a number of adverse events following use including disturbed sleep. Previous research has suggested that MDMA affects the circadian system, however, the acute effects following a single, moderate dose have not been well characterised. The current study investigated how MDMA affected the circadian system, as measured by the amount and temporal distribution of wheel-running activity in male rats (n=90), housed individually under a 12-12 h light-dark (LD) cycle prior to treatment. MDMA (5 or 10 mg/kg) or saline was administered in a single i.p. injection during the light phase of the LD cycle and post-treatment activity was monitored during subsequent LD cycles (Experiment 1), or under constant darkness (Experiment 2). MDMA treatment disrupted wheel running activity in both experimental paradigms. In Experiment 1, 10 mg/kg MDMA significantly increased the amount of activity during the rest phase on the day of treatment and 1-day post treatment. This was accompanied by a change in the distribution of activity across the LD cycle during the first 24 h period after treatment, without a change in the overall daily activity level. Experiment 2 found that MDMA affected the circadian system as reflected by changes in the duration of the active phase, tau and activity offset. As a single dose of MDMA was able to disrupt the circadian rhythmicity of locomotor activity, this finding has implications for other behaviours that are under circadian control including the sleep/wake cycle.