Steroid receptors in the brain: Topography and some functional implications.

The anatomical localization of brain cells which concentrate steroid hormones or their metabolites was carried out by radioautographic procedures. Ovariectomized or adrenalectomized animals were injected with the appropriate tritiated hormones, and brain tissue was processed through procedures which minimize the removal or displacement of steroids. Target cells were characterized by the concentration and retention of radioactive hormone in their nuclei. For each mammalian steroid hormone, nuclear binding sites exist in populations of cells with a specific regional localization in the brain and in the pituitary. The distribution of estrogen target cells was remarkably similar in the brains of rodents and primates although some minor species differences existed. Heavily labeled cells were present in the preoptic region, the septum, the amygdala and the mediobasal hypothalamus. The localization of progestagen-concentrating cells in the rodent and galago brain was limited to two hypothalamic areas: the preoptic region and the mediobasal hypothalamus. Corticosterone target cells were situated in extrahypothalamic regions of the rat central nervous system such as the hippocampus, the septum, the amygdala and certain regions of the brain cortex. However, the synthetic glucocorticosteroid, dexamethasone, was mainly found in the pituitary cells and in some neurons and glial cells of the mediobasal hypothalamus. The distribution pattern of steroid-sensitive cells within the brain and the pituitary gland corresponds to sites which are involved in the neuroendocrine processes regulating reproduction, including gonadotropin secretion and sexual behavior.