Effect of moclobemide on rat brain monoamine oxidase A and B: comparison with harmaline and clorgyline.

1. Effects of moclobemide (12.5, 25 and 50 mg/kg), harmaline (10 mg/kg) and clorgyline (10 mg/kg) on monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B) were examined ex vivo by a fluorometric method with tyramine (T) and phenylethylamine (PEA) as substrates. Six rat brain areas were dissected for this purpose. 2. Moclobemide had decreased MAO-A activity in all areas examined by a dose-dependent manner; the largest decrease was observed in tuberculum olfactorium and striatum. MAO-B activity after moclobemide had presented some dose-dependently inhibition (about 30 percent at a dose of 50 mg/kg). 3. Harmaline was more potent than moclobemide as MAO-A inhibitor but had left MAO-B activity unchanged. 4. Clorgyline was the most potent of the three drug tested for MAO-A inhibition. MAO-B activity was inhibited at the dose used in these experiments. 5. MAO-A inhibitory properties on tuberculum olfactorium and striatum could be of interest according to some animal models of depression.