Androgen and estrogen receptors in embryonic and neonatal rat brain

We provide biochemical evidence that specific androgen- and estrogen-binding macromolecules are present in rat hypothalamus-preoptic area throughout the "critical period' of brain sexual differentiation. Macromolecules with the properties of putative androgen and estrogen receptors are present in cytosolic extracts of embryonic neonatal, prepubertal rat hypothalamus-preoptic area and other brain regions. Both the androgen and estrogen receptors in perinatal rat brain are qualitatively similar to those in adult brain by virtue of their high affinity and limited capacity for hormone, specificity of hormone-binding, ability to adhere to DNA, differential behavior during DNA-cellulose affinity chromatography, behavior during velocity sedimentation, and tissue specificity. As early as 7 days before birth, both androgen and estrogen receptors are detectable in hypothalamus-preoptic area and other brain regions. Both receptors are more abundant in the hypothalamus-preoptic area relative to other regions. The concentrations of both receptors in hypothalamus-preoptic area increases as a function of age, although the relative rate of appearance of each receptor is distinctive: estrogen receptor concentrations increase approximately 6-fold during the last week of gestation, approximately adult-like levels at birth; androgen receptor concentrations increase slightly during late gestation, gradually rising to adult-like levels a few weeks after birth. The ontogeny profiles of both receptors from rat hypothalamus-preoptic area are compared with those from mouse. The presence of sex hormone receptors in perinatal rodent brain is discussed in the context of the hormonal milieu of perinatal rodent brain, and its effects on sexual differentiation of neural organization. The coincident appearance of receptors and post-mitotic neurons in prenatal rodent brain may indicate that sex hormones effect the early differentiation of these neurons.