Differences in the locomotor-activating effects of indirect serotonin agonists in habituated and non-habituated rats

► Studies examined whether the effects of MDMA are dependent on the novelty of the test environment. ► The ability of MDMA to induce locomotor hyperactivity was attenuated by habituation to the test environment. ► The effect of habituation on the locomotor response to MDMA varied over the light-cycle.