Effect of the chronic administration of ethinyl estradiol and norgestrel on biogenic amine(s) level and monoamine oxidase enzyme activity in rat brain

Abstract

Adult female virgin rats were administered contraceptive steroids orally for a long period, and the effect of this on the brain biogenic amine(s) content was studied. The amine(s) content of the brain during the course of chronic treatment with the hormones was estimated at various time intervals. In addition to this, the noradrenaline (NA) and 5-hydroxytryptamine (5-HT) content of rat brain regions was assayed after three months of hormone treatment. The onset of the brain amine depletion was observed by the end of the second month of hormone administration. The amine(s) depleting action was found to be due to the norgestrel component of the pill. Studies of the regional distribution of amine(s) showed that the depletion was more prominent in the hypothalamus and pons/medulla oblongata. The assay of the monoamine oxidase enzyme did not reveal any significant change, though the estrogenic and progestogenic hormones were found to have opposing effects on the enzyme levels.