Effects of melatonin on the ovarian response to pinealectomy or continuous light in female rats: similarity with polycystic ovary syndrome

Abstract

The current study was conducted to investigate the relationship between melatonin and chronic anovulation. Adult (3-4 months old) female Wistar rats were submitted to pinealectomy: group I: pinealectomized ovariectomized melatonin-treated (N = 10); group II: pinealectomized ovariectomized placebo-treated (N = 12); group III: pinealectomized light-treated placebo-treated (N = 10) or maintained under continuous light; group IV: maintained under continuous light, ovariectomized melatonin-treated (N = 22); group V: maintained under continuous light, ovariectomized placebo-treated (N = 10); group VI: maintained under continuous light placebo-treated (N = 10). In order to assess ovarian modifications, unilateral ovariectomy was performed during the fourth month in groups I, II, IV, V and the other ovary was removed after 8 months. Ovariectomy was performed in groups III and VI only after eight months. Melatonin (200 µg/100 g body weight) dissolved in 0.02 ml absolute ethanol was injected intramuscularly daily during the last 4 months into groups I and IV. The other groups were treated with placebo (NaCl). The ovarian cysts were analyzed and their area, perimeter and maximum diameter, as well as the thickness of the ovarian capsule were measured. Daily colpocytological smears were performed throughout the study. Persistent estrous condition and ovarian cysts were observed in all groups. In pinealectomized rats the ovarian and vaginal alterations disappeared at the end of the study and in rats maintained under continuous light the vaginal and ovarian polycystic aspect was reversed only in those treated with melatonin. We conclude that melatonin may act on the ovarian response reverting chronic anovulation induced by pinealectomy or continuous light.

Long-Term Exogenous Melatonin Treatment Modulates Overall Feed Efficiency and Protects Ovarian Tissue Against Injuries Caused by Ethanol-Induced Oxidative Stress in Adult UChB Rats

“…It is known that melatonin dissolved in drinking water can increase the frequencies of diestrous or estrous phases in rodents (Kachi et al., 2006) by modulation of GnRH hormones. Furthermore, rats receiving melatonin (200 μg/100 g BW/d) showed longer estrous periods, reduction in polycystic ovary syndrome, and ovary weight (Prata Lima et al., 2004). As seen before, there may also be a positive interaction between ethanol and melatonin for decreasing ovarian weights, because they act on reproduction‐linked hormones.…”

Protective effects of melatonin against metabolic and reproductive disturbances in polycystic ovary syndrome in rats

“…It also resulted in a persistent estrous condition and downregulation of GLUT4, which is an insulin‐dependent glucose transporter [4]. Similar exposure of rats to 500 lux intensity light for 10–12 weeks resulted in persistent estrus condition [5]…”

Combination of Melatonin and Metformin Hydrochloride for Treatment Polycystic Ovarian in Female Rats

“…This is associated with the ability of melatonin to regulate the hypothalamic axis, inhibiting the release of hormones such as follicle stimulating hormone, which aids in the reduction of cysts. Additionally, has anti-inflammatory and antitoxic effects, acts against free radicals, and reduces cytokines that are part of the activation process of the synthesis by fibroblasts [24,25]. Another function of melatonin is to regulate the gonadotropin releasing hormone (GnRH) through its MT1 and MT2 receptors, which are members of receptors coupled to the G 7-transmembrane protein in the granulosa luteal cells, that inhibit GnRH receptor expression and preserve the corpus lutea, and consequently increase progesterone production [21,39].…”

“…After the rats were weighed, rats from group III and group V were treated with melatonin in accordance with the methodology described by Prata-Lima et al [25]. (Melatonin)² was administered at a dose of 200 μg/100 g b.w.…”