Topographical distribution of estrogen target cells in the forebrain of platyfish, Xiphophorus maculatus, studied by autoradiography.

In the platyfish, Xiphophorus maculatus, after injection of [3H]estradiol-17 beta, nuclear concentration of radioactivity is observed in certain cells of the forebrain. These labeled cells are accumulated in periventricular midline regions that include in the telencephalon the ventral precommissural and dorsal supracommissural areas, and in the diencephalon the preoptic, central hypothalamic and thalamic areas. The specialized ependyma of the subcommissural organ also shows nuclear concentration of radioactivity, while other ependymal cells remain unlabeled. Similar to other vertebrate classes, the accumulations of estrogen target cells exist characteristically in the vicinity of the ventricular system, especially its recesses. This implies close topographical relationships between estrogen target cells and the ventricular recess organs, including the optic recess organ, the infundibular recess organ, the paraventricular organ and the subcommissural organ. Different from other vertebrate classes, no pallial accumulations of estrogen target cells are seen in the teleost.