Drug Alcohol Depend 2013 Dec 23;133(2):746-50. Epub 2013 Jul 23.
Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA, USA; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA, USA.
Background: The present study tested the hypothesis that mephedrone (MEPH) produces behavioral sensitization (i.e., a progressive increase in motor response during repeated psychostimulant exposure) in rats.
Methods: MEPH was administered in two paradigms: (1) a 7-day variable-dosing paradigm (15 mg/kg on the first day, 30 mg/kg for 5 days, 15 mg/kg on the last day) and (2) a 5-day constant-dosing paradigm (15 mg/kg for 5 days). Following 10 days of drug absence, rats were challenged with MEPH (15 mg/kg).
Results: MEPH challenge produced enhancement of repetitive movement compared to acute MEPH exposure in both paradigms. Sensitization of repetitive movements to MEPH was also detected following a shorter (2-day) absence interval, before initiation of an absence interval (i.e., following repeated daily exposure), and across context-independent and -dependent dosing schedules. A lower dose of MEPH (5mg/kg) did not produce sensitization of repetitive movement. Sensitization of ambulatory activity was not detected in any experimental paradigm.
Conclusion: These results suggest that repeated MEPH exposure produces preferential sensitization to repetitive movement produced by acute MEPH challenge. Our findings suggest that MEPH is a unique stimulant displaying weak sensitizing properties with overlapping, but distinctive, features relative to established psychostimulant drugs.