Influence of the pineal extract and melatonin on the estrous cycle of the mice

ABSTRACT

This work was undertaken to study the effects of daily injections of pineal extract of camel and melatonin for 21 days on the estrous cycle in mice. Daily injections of either 1.5 ml pineal extract or 100 micro g. melatonin -significantly reduced the number of the estrous cycles per animal and the length of these cycles were significantly prologed. Days in proestrus and estrus were significantly decreased. Days in metestrus were not affected. All animals injected with either pineal extract or melatonin spend proportionately more significant time in diestrus phase. When the animals were paired with fertile males, mice seemingly mated as soon as they came into estrus. However, both pineal extract and melatonin treatment inhibited fertile matings. Pineal extract and melatonin showed no effect on the induced estrous cycles when oestradiol and progesterone were given with these agents in ovariectomized mice. Both pineal extract and melatonin significantly increased the release of oestradiol and progesterone. Histological examination of the ovaries of pineal extract and melatonin treated animals revealed the presence of several graafian follicles in different stages of maturation. The interstitial tissue dominate the ovary. The results showed that the estrous cycles of mice were interrupted and ovulation decreased after daily injections of either pineal extract or melatonin for 21 days. It is concluded that pineal gland plays an important physiological role in the regulation of ovarian function as well as estrous cyclicity in female mice. Also, melatonin may be one of the factors modulating the effect of pineal gland on estrous cycle