Protective effects of minocycline on behavioral changes and neurotoxicity in mice after administration of methamphetamine.

The effects of minocycline on behavioral changes and neurotoxicity in the dopaminergic neurons induced by the administration of methamphetamine (METH) were studied. Pretreatment with minocycline (40 mg/kg) was found to attenuate hyperlocomotion in mice after a single administration of METH (3 mg/kg). The development of behavioral sensitization after repeated administration of METH (3 mg/kg/day, once daily for 5 days) was significantly attenuated by pretreatment with minocycline (40 mg/kg). A reduction in the level of dopamine (DA) and its major metabolite, 3,4-dihydroxyphenyl acetic acid (DOPAC), in the striatum after the repeated administration of METH (3 mg/kg x 3, 3-h interval) was attenuated in a dose-dependent manner by pretreatment with and the subsequent administration of minocycline (10, 20, or 40 mg/kg). Furthermore, minocycline (40 mg/kg) significantly attenuated a reduction in DA transporter (DAT)-immunoreactivity in the striatum after repeated administration of METH. In vivo microdialysis study demonstrated that pretreatment with minocycline (40 mg/kg) significantly attenuated increased extracellular DA levels in the striatum after the administration of METH (3 mg/kg). In addition, minocycline was not found to alter the concentrations of METH in the plasma or the brain after three injections of METH (3 mg/kg), suggesting that minocycline does not alter the pharmacokinetics of METH in mice. Interestingly, METH-induced neurotoxicity in the striatum was significantly attenuated by the post-treatment and subsequent administration of minocycline (40 mg/kg). These findings suggest that minocycline may be able to ameliorate behavioral changes as well as neurotoxicity in dopaminergic terminals after the administration of METH. Therefore, minocycline could be considered as a useful drug for the treatment of several symptoms associated with METH abuse in humans.