Effect of a neurotoxic dose regimen of (+)-methamphetamine on behavior, plasma corticosterone, and brain monoamines in adult C57BL/6 mice

RationaleIn rats, neurotoxic doses of methamphetamine (MA) induce astrogliosis, long lasting monoamine reductions, reuptake transporter down-regulation, and learning impairments.ObjectiveWe tested whether comparable effects occur in C57BL/6 mice.MethodC57BL/6 mice were treated with 10 mg/kg s.c. × 4 MA on a single day and evaluated at various intervals thereafter.ResultsThe neurotoxic dose regimen of MA caused the predicted acute hyperthermia and increased striatal glial fibrillary acidic protein and reduced neostriatal dopamine. The MA-treated mice were hypoactive 24 h later but not 48 h later. MA-treated mice also showed exaggerated initial hyperactivity after a pharmacological dose of MA used to stimulate locomotion followed by a later phase of hypoactivity compared to saline-treated mice. No differences were observed on learning or memory tests (novel object recognition, egocentric, or spatial learning/memory). MA-treated mice showed a trend toward increased prepulse inhibition but not baseline acoustic startle reactivity. After testing, MA-treated mice showed reduced neostriatal dopamine and increased basal plasma corticosterone.ConclusionsA neurotoxic/binge regimen of MA in mice that produces the typical pattern of neurotoxic changes to those seen in rats, results in few behavioral changes. This may limit the utility of C57BL/6 mice for modeling the cognitive and behavioral effects described in human MA users who show such changes even after prolonged abstinence.