Mephedrone (4-methylmethcathinone) is a still poorly known drug of abuse, alternative to ecstasy or cocaine. The major aims were to investigate the pharmacokinetics and locomotor activity of mephedrone in rats and provide a pharmacokinetic/pharmacodynamic model. Mephedrone was administered to male Sprague–Dawley rats intravenously (10 mg/kg) and orally (30 and 60 mg/kg). Plasma concentrations and metabolites were characterized using LC/MS and LC-MS/MS fragmentation patterns. Locomotor activity was monitored for 180–240 min. Mephedrone plasma concentrations after i.v. administration fit a two-compartment model (α = 10.23 h⁻¹, β = 1.86 h⁻¹). After oral administration, peak mephedrone concentrations were achieved between 0.5 and 1 h and declined to undetectable levels at 9 h. The absolute bioavailability of mephedrone was about 10 % and the percentage of mephedrone protein binding was 21.59 ± 3.67 %. We have identified five phase I metabolites in rat blood after oral administration. The relationship between brain levels and free plasma concentration was 1.85 ± 0.08. Mephedrone induced a dose-dependent increase in locomotor activity, which lasted up to 2 h. The pharmacokinetic–pharmacodynamic model successfully describes the relationship between mephedrone plasma concentrations and its psychostimulant effect. We suggest a very important first-pass effect for mephedrone after oral administration and an easy access to the central nervous system. The model described might be useful in the estimation and prediction of the onset, magnitude, and time course of mephedrone pharmacodynamics as well as to design new animal models of mephedrone addiction and toxicity.

This study was undertaken to investigate whether kainic acid (KA) may regulate the expression of several proteins which plays an important role in cell-cycle progression in cerebellar granule neurons (CGNs). KA induced decrease in MTT values in a concentration dependent way. Flow cytometric analysis showed that KA was able to induce 30% apoptosis in CGNs. Apoptotic nuclear condensation were detected 24 h of exposure to KA (200 microM). An associated marked increase in DNA synthesis, measured by BrdU incorporation, was observed. Western blot analysis showed that KA induced an increase in the expression of Cdk2, cyclin E and E2F-1. It is proposed that, in post-mitotic cells like CGNs, re-entry cell cycle could be responsible for the apoptotic effect of KA.