Autoradiographic techniques and the localization of estrogen, androgen, and glucocorticoid in the pituitary and brain

Abstract

SYNOPSIS. Autoradiographic techniques are reviewed which have been recommended. for the localization of diffusible substances, such as steroid hormones. Advancement in techniques, including low temperature tissue sectioning, section freeze-drying, and dry-mounting of sections, led to the development of the dry-mount autoradiographic technique. This progress in technique has enabled the cellular and subcellular topotgraphic localization of steroid hormones in peripheral and central target tissues, including the identification of hormone target cells in the pituitary and mapping of hormone neurons in the brain. In the pituitary, tritiated estrogen, androgen, and glucocorticoid are concentrated and retained in nuclei of certain anterior lobe cells. In the brain, estrogens, androgens, and glucocorticoids are attracted by and concentrated in nuclei of certain neurons located mainly within the phylogenetically old periventricular brain. In view of the widespread distribution of sex steroids in different brain areas, the generally held concept of a topographically confined single or dual “sex center” is challenged. While estrogen and androgen neurons in the hypothalamus, in the preoptic-septal-parolfactory region, and in the amygdala overlap, or are even identical in part, glucocorticoid neurons are more heavily concentrated in the gyrus dentatus, hyppocampus, indusium griseum, dorsal nuclei septi lateralis and medialis, as well as in the piriform cortex and portions of the amygdala. It is conceptualized that the steroid hormone neurons are hypophysiotropic neurons, being involved in the neurosecretion of releasing factors, and that they represent sought for hormone “feedback” areas in the brain. This challenges the generally held view of the “hypophysiotrophic area” in the hypothalamus as the anatomical site where releasing factors are produced.