The effect of N-methyl-norsalsolinol on monoamine oxidase of the rat caudate nucleus in vitro.

The effects of N-methyl-norsalsolinol on basal and inhibited activity of monoamine oxidase (MAO) in membrane preparations from the caudate nucleus of the rat have been studied. For the first time, the physiological step of dopamine oxidation to 3, 4 dihydroxyphenylacetic aldehyde (DPAA) was examined. N-methyl-norsalsolinol (2-MDTIQ) dose-dependently inhibited MAO activity with a IC50 of 33 microM. The MAO inhibitors clorgyline and deprenyl were also found to inhibit formation of DPAA. In this case, the inhibition of these antagonists, clorgyline and deprenyl, was additive. N-methyl-norsalsolinol modified neither the enzyme inhibition induced by clorgyline nor by deprenyl. These results suggest that 2-MDTIQ, the naturally occurring compound found in parkinsonian brain and cerebrospinal fluid, perturbs dopamine metabolism in basal ganglia.