Effect of photoperiod and pineal indoles on the reproductive system of young female white-footed mice.

Exposure of prepubertal female mice to short photoperiod (LD 8:16) for 3 weeks resulted in a significant inhibition of reproductive tract growth compared with mice maintained in long photoperiod (LD 16:8). Chronic subcutaneous melatonin-beeswax implants containing 1 mg melatonin also produced an inhibition of the reproductive system of these animals. The repressive effects of melatonin appear not to be influenced by photoperiod since comparable results were obtained from groups of mice bearing implants in long and short photoperiods. In addition, the ability of beeswax implants containing various indolic compounds (melatonin, serotonin, 5-methoxytryptamine, 5-methoxyindole-3-acetic acid, and N-acetylserotonin) to inhibit the growth of the reproductive system of this species were compared. Only implants containing melatonin or serotonin caused any significant repression of uterine and ovarian weights.