Monoamine oxidase-B inhibitors in the treatment of Alzheimer's disease.

The monoamine oxidase-B (MAO-B) inhibitor L-deprenyl (Selegiline) is effective in treating Parkinson's disease and possibly Alzheimer's disease, with a concomitant extension of life span. It has been suggested that the therapeutic efficacy of L-deprenyl may involve actions other than the inhibition of the enzyme MAO-B. This article reviews some novel actions of L-deprenyl and suggests that stimulation of nitric oxide (NO) production could be central to the action of the drug. L-Deprenyl induced rapid increases in NO production in brain tissue and cerebral blood vessels. In vitro or in vivo application of L-deprenyl produced vasodilatation. The drug also protected the vascular endothelium from the toxic effects of amyloid-beta peptide. Because NO modulates activities including cerebral blood flow and memory, and reduced NO production has been observed in AD brain, stimulation of NO production by L-deprenyl could contribute to the enhancement of cognitive function in AD. MAO-B inhibitors are unique in that they exert protective effects on both vascular and neuronal tissue and thus warrant further consideration in the treatment of vascular and neurodegenerative diseases associated with aging.