Possible melatonin involvement in the hypotensive effect of MAO inhibitors.

Effect of selective inhibitors of MAO-A and B isoenzymes on pineal melatonin (and related indoles), arterial blood pressure and brain MAO-A and B activities has been evaluated in intact, pinealectomized and sham-operated rats. Selective inhibition of MAO-A but not MAO-B activity stimulated pineal melatonin synthesis and decreased arterial blood pressure in intact and sham-operated animals. Pinealectomy attenuated the hypotensive effect of MAO-A inhibition. The possible melatonin contribution to both antidepressive and hypotensive effects of MAO inhibitors is discussed.