Neonatal injections of methoxychlor decrease adult rat female reproductive behavior.

Area of Science:

• Endocrinology
• Reproductive Toxicology
• Environmental Health

Background:

• Methoxychlor (MXC) is a widely used pesticide recognized as an endocrine disruptor.
• Neonatal exposure to endocrine-disrupting chemicals can have long-lasting effects on reproductive health.

Purpose of the Study:

• To investigate the impact of neonatal methoxychlor exposure on female rat reproductive characteristics.
• To determine if methoxychlor exhibits estrogenic activity during the critical neonatal developmental window.

Main Methods:

• Female Sprague-Dawley rats received subcutaneous injections of methoxychlor (1.0mg or 2.0mg), 17β-estradiol benzoate (positive control), or sesame oil (vehicle) on postnatal days 1, 3, and 5.
• Evaluated anogenital distance, vaginal opening, vaginal keratinization, and adult mating behaviors.

Main Results:

• Methoxychlor exposure did not affect anogenital distance or the timing of vaginal opening.
• A significant increase in vaginal keratinization days was observed with 2.0mg MXC and estradiol treatments.
• Adult mating behaviors showed no effect on mating response, but high-dose MXC and estradiol decreased receptivity and proceptive behaviors while increasing rejection.

Conclusions:

• Neonatal exposure to higher doses of methoxychlor can mimic estrogenic effects.
• Methoxychlor alters adult reproductive characteristics by impacting the nervous system, affecting sexual receptivity and behavior.