Effects of N-ethylpentylone on locomotor activity and anxiety-like behavior in rats.

N-ethylpentylone (NEP), a new synthetic cathinone, has been rising to be one of the most popular cathinone derivatives in recent years. However, research on NEP is rather limited. In this study, locomotor stimulation and sensitization, as well as anxiety-like behavior induced by NEP were studied in Sprague-Dawley rats, using the open field and elevated plus maze respectively. Rats were administered NEP (5, 20 or 50 mg/kg, intraperitoneal), with saline as the negative control and methamphetamine (5 mg/kg) as a positive control. Acute administration of NEP at all the doses tested significantly promoted locomotor activity, presenting an inverted U-shaped dose-effect curve. The highest activity was observed at the 20 mg/kg dose group, with the average distance traveled 18 times higher than the saline group. Repeated administration of NEP enhanced locomotor activity only at the 5 mg/kg dose group. After a week's withdrawal, re-challenge of NEP failed to induce marked behavioral sensitization. In elevated plus maze experiments, both acute and repeated administration of 20 mg/kg NEP induced anxiolytic-like effects, while no significant alteration was observed in the 5 and 50 mg/kg dose groups. In summary, acute administration of NEP caused significantly enhanced locomotor activity in rats at all the tested doses, while repeated NEP administration enhanced locomotor activity only at a low dose (5 mg/kg), while a high dose (20 mg/kg) of NEP induced anxiolytic-like effects after both acute and repeated administration.