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Keywords:

  • Monoamine oxidase (MAO) A and B;
  • brain;
  • liver;
  • small intestine;
  • selegiline (l-deprenyl);
  • clorgyline;
  • rasagiline;
  • irreversible inhibitors;
  • Parkinson's disease;
  • dopamine
  • Rasagiline [N-propargyl-1R(+)-aminoindan], was examined for its monoamine oxidase (MAO) A and B inhibitor activities in rats together with its S(−)-enantiomer (TVP 1022) and the racemic compound (AGN-1135) and compared to selegiline (1-deprenyl). The tissues that were studied for MAO inhibition were the brain, liver and small intestine.

  • While rasagiline and AGN1135 are highly potent selective irreversible inhibitors of MAO in vitro and in vivo, the S(−) enantiomer is relatively inactive in the tissues examined.

  • The in vitro IC50 values for inhibition of rat brain MAO activity by rasagiline are 4.43±0.92 nM (type B), and 412±123 nM (type A). The ED50 values for ex vivo inhibition of MAO in the brain and liver by a single dose of rasagiline are 0.1±0.01, 0.042±0.0045 mg kg−1 respectively for MAO-B, and 6.48±0.81, 2.38±0.35 mg kg−1 respectively for MAO-A.

  • Selective MAO-B inhibition in the liver and brain was maintained on chronic (21 days) oral dosage with ED50 values of 0.014±0.002 and 0.013±0.001 mg kg−1 respectively.

  • The degree of selectivity of rasagiline for inhibition of MAO-B as opposed to MAO-A was similar to that of selegiline. Rasagiline was three to 15 times more potent than selegiline for inhibition of MAO-B in rat brain and liver in vivo on acute and chronic administration, but had similar potency in vitro.

  • These data together with lack of tyramine sympathomimetic potentiation by rasagiline, at selective MAO-B inhibitory dosage, indicate that this inhibitor like selegiline may be a useful agent in the treatment of Parkinson's disease in either symptomatic or L-DOPA adjunct therapy, but lack of amphetamine-like metabolites could present a therapeutic advantage for rasagiline.

British Journal of Pharmacology (2001) 132, 500–506; doi:10.1038/sj.bjp.0703826