Ovulatory patterns in female mice following treatment with melatonin

ABSTRACT

Intraperitoneal injection of melatonin inhibited ovulation in the normal cyclic mice when injected on the proestrus phase. Greater effect was obtained when melatonin was injected at 1,2,3 and 4 pm proestrus day and maximum effect was obtained when the animals were injected with l mg/injection. The administration of melatonin in a dose of 4 mg [1 mg/injection] at 1,2,3 and 4 pm on the proestrus phase of the oestrus cylcle in mice decreased the average number of recent corpora lutea and the average number of lutein cells by 100%. Histological examination of the ovaries of melatonin treated animals showed no evidence of preovulatory swelling of the follicles. Injection of the same dose of melatonin [4 mg] significantly decreased serum proestrus progesterone and oestradiol-17 B level by 2.61% and 29.99% respectively. The serum level of dioestrus progesterone and oestradiol-17 B was significantly decreased by 45.56% and 37.86% respectively. The administration of another low dose [2 mg] led to a weaker effect on the ovary than the highest dose. It can be concluded that melatonin proved to have antiovulatory effect in mice The antiovulatory effect may be due to lowering level of LH either directly - through an inhibitory action on the anterior pituitary gland, or indirectly through either decreasing the secretion of LH releasing hormone from the hypothalamus or decreased levels of serum proestrus progesterone and oestradiol-17 B by direct action on the ovary