Biochemical effects of the monoamine neurotoxins DSP-4 and MDMA in specific brain regions of MAO-B-deficient mice

In mice lacking the enzyme monoamine oxidase B (MAO-B), the neurotoxin DSP-4 caused the same loss of norepinephrine in brain regions as it did in normal mice, indicating MAO-B is not involved in DSP-4 toxicity. For the neurotoxin MDMA (ecstasy), MAO-B deficiency prevented the serotonin depletion normally seen in wild-type mice but led to a more pronounced dopamine loss. These results suggest MAO-B plays opposite roles in MDMA-induced damage to dopamine and serotonin systems.

Study at a glance

Abstract

Previous studies reported that drugs acting as monoamine oxidase (MAO)-B inhibitors prevented biochemical effects induced by the neurotoxins N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) and 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy"). In this study, we administered DSP-4 (50 mg/kg) or MDMA (50 mg/kg x 2, 2 h apart) to MAO-B deficient mice. Monoamine content in various brain regions (cerebellum, frontal cortex, hippocampus, hypothalamus, striatum, substantia nigra) was assayed 1 week after neurotoxin administration. Injection of DSP-4 to wild-type mice caused a marked norepinephrine (NE) loss in specific brain regions. Unexpectedly, DSP-4 caused similar effects in MAO-B-deficient and in wild-type mice in all brain regions investigated. These results suggest that MAO-B is not involved in DSP-4 toxicity. In wild-types, the neurotoxin MDMA induced both serotonin (5HT) and dopamine (DA) depletion in specific brain areas. In MAO-B-deficient mice, 5HT depletion observed in wild-types did not occur. In contrast, MDMA produced a more pronounced DA loss in knockout mice compared with wild-types. The present findings, together with previous data obtained using selective enzyme inhibitors, suggest that MAO-B is not involved in the mechanism of action of DSP-4, whereas it plays opposite roles in MDMA-induced DA and 5HT depletions.