Effects of morphine and methadone on the nuclear uptake of estradiol by the brain.

Rats were treated for ten days with morphine (50 microgram/kg) or methadone (10 mg/kg). On the tenth day the animals were injected with 3H-estradiol, and the nuclear uptake of the steroid by the central nervous system was evaluated by autoradiography. Neither of the opiates were found to have any significant effect on the nuclear uptake of 3H-estradiol by the central nervous system. The data suggest that the mechanism by which methadone and morphine inhibit normal reproductive function in addicts is probably not the inhibition of nuclear uptake of estradiol.