Rats were pretreated with GR 127935 (2.5 mg/kg) or β-cyclodextrin vehicle (2 ml/kg) 45 min prior to an injection of (+)-MDMA (3 mg/kg) or saline (1 ml/kg). After a 48-h withdrawal, the hyperactivity evoked by challenge with RU 24969 (2 mg/kg) was assessed. Twenty-four hours after the RU 24969 challenge, rats were anesthetized with chloral hydrate (800 mg/kg i.p.) and decapitated. The frontal cortex was dissected and the tissue was stored at −80°C until assay.