Neurotoxins and monoamine oxidase inhibition: New aspects

Authors

  • Prof. K. T. Finnegan

    Corresponding author
    1. Departments of Psychiatry, Pharmacology, and Toxicology, University of Utah School of Medicine, and the Psychiatry Service, Veterans Administration Medical Center, Salt Lake City, Utah, U.S.A.
    • Psychiatry Service (116A), Veterans Administration Medical Center, Salt Lake City, UT 84148, U.S.A
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Abstract

Recent clinical studies suggest that selegiline (L-deprenyl) is useful in retarding the progress of Parkinson's disease, an effect that may be related to its inhibition of monoamine oxidase type B (MAO-B). Selegiline is also reported to prevent the toxic effects of the noradrenergic neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). This article reviews recent studies on the role of MAO-B and its inhibition in this neuroprotective action of selegiline. Male C57Bl/6 mice were given DSP-4 (50 mg/kg) 1 h, 24 h, or 4 days after the administration of selegiline (10 mg/kg) or the selective MAO-B inhibitor MDL 72974 (1.25 mg/kg) and then killed 1 week later for the assay of norepinephrine in hippocampus. The MAO-B-inhibiting effects of selegiline or MDL 72974 were also determined after these same intervals. Selegiline and MDL 72974 produced comparable degrees of enzyme inhibition 1 h (>95%), 24 h(>90%), or 4 days (>70%) after their administration. Given 1 h before, selegline totally bloked the norepinephrinedepleting effects of DSP-4, but this protection declined sharply when 24 h or 4 days was allowed to elapse between selegiline and DSP-4 administration. MDL 72974 failed to protect at any time point. In vitro, no activity was observed when DSP-4 was used as a substrate for MAO. All of these findings suggest that the ability of selegiline to protect against DSP-4-induced neuronal degeneration does not depend on its inhibition of MAO-B.

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