Sexual Differentiation of the Brain: Effects on Mating Behavior and [3H]-Estradiol Binding by Hypothalamic Chromatin in Rats

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Abstract
It was determined whether previously observed sex differences in the binding of [3H]estradiol [E2] by hypothalamic nuclear chromatin material could be influenced by hormonal manipulation at birth that alters adult sexual potential. Male rats were castrated at birth or 10 days after birth; females were administered oil or 500 .mu.g testosterone propionate at birth, examined for vaginal cyclicity at maturity and then ovariectomized. All animals were given estrogen and progesterone and tested for the occurrence of lordosis behavior. Following hormone withdrawal, they were given [3H]E2 i.v., and the binding of [3H]E2 by hypothalamic and cortical chromatin 30 min later was determined. Females castrated at maturity and males castrated at birth showed high levels of lordosis behavior and high levels of E2 binding by hypothalamic chromatin. Neonatally androgenized females and males castrated 10 days after birth showed low levels of lordosis behavior and a reduction in hypothalamic chromatin binding relative to these parameters in control females. Chromatin binding of E2 in the cortex was low in all groups.