Characterization of estrogen-concentrating hypothalamic neurons by their axonal projections.

A method combining steroid autoradiography and fluorescent dye retrograde neuroanatomical tracing has been devised. This method makes it possible to demonstrate that some estrogen-concentrating cells in the ventrolateral subdivision of the ventromedial nucleus of the rat hypothalamus are neurons that send axons to the dorsal midbrain. Other cells only concentrate estrogen or only project to the midbrain. Estrogen-concentrating neurons in the ventromedial hypothalamus that project to the dorsal midbrain are likely to transmit hormone-influenced signals that regulate circuits for reproductive or other behaviors or autonomic functions.