Behavioral sensitization following concurrent exposure to mephedrone and D-amphetamine in female mice

Recreational use of illicit methcathinone derivatives is a public health concern in the USA and Europe. Recent reports indicate that mephedrone (MEPH) produces neurochemical and behavioral effects comparable with amphetamines. The present study investigated the effects of a mixture of MEPH and D-amphetamine (AMPH) on the induction and expression of behavioral sensitization. Thirty female CD-1 mice received seven subcutaneous injections of saline, AMPH (1.0 mg/kg), MEPH (3.0 mg/kg), or AMPH (1.0 mg/kg)+MEPH (3.0 mg/kg) over an 8-day period with 48 h between the first and second injection and 24 h between subsequent injections. Activity was assessed immediately following the first and seventh dose. After a 10-day washout, 1.0 mg/kg AMPH was administered to all animals and activity was assessed in a similar manner. Compared with mice treated with AMPH or MEPH, those treated with AMPH+MEPH displayed stronger indices of behavioral sensitization after the seventh dose and in response to AMPH after the washout period. These results suggest that MEPH may enhance sensitivity to the behavioral effects of AMPH. Considered in light of findings that MEPH has comparable neurochemical actions to the amphetamines and is commonly used with other stimulants, further research on the abuse liability of drug mixtures with methcathinones and other psychostimulants is warranted.