Neonatal Exposure to Melatonin Favours Follicular Survival and Increases Fecundity in the Female Rat

Rat neonates have been exposed to melatonin by i.p. injection of 40(19 melatonin/animal/day daily in the evening at 16:30 hrs from day 0 to day 21. The preweaning hypeimelatonemia did not significantly influence either adult body weight or ovarian weight. The estrogen titre was reduced and progesterone titre increased in melatonin treated rats. Increased thyroid weight and elevated thyroid hormones levels were also recorded. The primordial and primary follicles were more in number with significantly lesser atretic follicles of all developmental stages. The first litter size was significantly greater (lit 3 vs 8 ± 2) in melatonin treated rats compared to controls. These results are interpreted in terms of protective action of neonatal melatonin against follicular apoptosis either directly or indirectly through thyroid hormones.