Changes in estrogen-a receptor immunoreactivity during the estrous

Estradiol is one of the most important hormones in the regulation of estrous behavior, which is at a very low level of expression in the modern dairy cow. In the present study the neuroanatomical distribution of estrogen receptors of the a-subtype (ER-a) in the bovine hypothalamic area is determined with immunocytochemical methods, at various stages of the estrous cycle. During the luteal phase of the cycle, ER-a immunoreactive cells were found in most of the nuclei that are known to express ER-a immunoreactivity in other species, like the Bed nucleus of the Stria terminalis, Medial preoptic area, Ventromedial hypothalamus and Arcuate nucleus. During estrus and metestrus, however, no ER-a immunoreactive cells could be detected in those areas, except for a few in the caudal Arcuate nucleus. The results from the present study indicate that there is a coherent regulation and timing of physiological and behavioral events around ovulation, in which estradiol and its receptor play a key role.  2000 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Hormonal control of reproductive behavior