CHRONIC EFFECT OF THE IRREVERSIBLE AND REVERSIBLE SELECTIVE MAO-A INHIBITORS ON RAT PINEAL MELATONIN BIOSYNTHESIS

Acute administration of the irreversible MAO-A inhibitor, clorgyline ( 2.0 mg/kg, s.c.) and the reversible MAO-A inhibitor, moclobemide (10 m g/kg, s.c.), increased rat pineal melatonin and related indoles conten t (HPLC-fluorimetric method). Chronic (21 days) administration of clor gyline attenuated the acute effect of clorgyline on pineal melatonin b iosynthesis. The acute effect of moclobemide on melatonin biosynthesis was not affected by chronic moclobemide administration. The observed difference in the chronic effects of irreversible and reversible selec tive MAO-A inhibitors on melatonin biosynthesis could have clinical im plications.