Changes in estrogen-alpha receptor immunoreactivity during the estrous cycle in lactating dairy cattle

Estradiol is one of the most important hormones in the regulation of estrou s behavior, which is at a very low level of expression in the modern dairy cow. In the present study the neuroanatomical distribution of estrogen rece ptors of the alpha -subtype (ER-alpha) in the bovine hypothalamic area is d etermined with immunocytochemical methods, at various stages of the estrous cycle. During the luteal phase of the cycle, ER-alpha immunoreactive cells were found in most of the nuclei that are known to express ER-alpha immuno reactivity 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-alpha immunoreactive cells could be d etected in those areas, except for a few in the caudal Arcuate nucleus. The results from the present study indicate that there is a coherent regulatio n and timing of physiological and behavioral events around ovulation, in wh ich estradiol and its receptor play a key role. (C) 2000 Elsevier Science B .V. All rights reserved.