RESUMO
Monoamineoxidase (MAO) activity in some regions of brain and urinary xanthurenic acid were investigated in female rats administered with oral contraceptive (OC) steroids-ethynyl estradiol (Ees), lynestrenol (Ly) and both in combination (Cm) for 75 days. The MAO activity was reduced significantly in most regions specially in cortex-the extent of reduction being 65 per cent with Ees, 51 per cent with Ly and 69 per cent with Cm treatments. In the hypothalamus, the activity was decreased by 50 per cent with Ees, 38 per cent with Ly and by 40 per cent with Cm treatments. In the corpus striatum the activity was reduced by 14 per cent with Ly treatment, 25 per cent with Cm treatment and in the midbrain by 59 per cent with Ees treatment only. The concentration of xanthurenic acid in urine was higher by 55 per cent with Ees, 109 per cent with Ly and by 120 per cent with Cm treatments. These changes in MAO activity and level of xanthurenic acid excretion indicate the possible alteration in the metabolism of neurotransmitter, associated with prolonged use of OC.