This study was undertaken to reveal whether integration of the periphe
ral signals, leptin and estradiol, that convey information on the meta
bolic state and gonadal function, respectively, might occur in the sam
e hypothalamic neuronal perikarya. Light and electron microscopic immu
nolabeling for leptin receptors (LRs) and estrogen receptors (ERs) was
carried out on hypothalamic sections of female rats. In the medial pr
eoptic area, periventricular regions, including the parvicellular para
ventricular nucleus, the arcuate nucleus and the ventromedial hypothal
amic nucleus, all of the cells that expressed immunoreactivity for ERs
were also immunopositive for LR. On the other hand, only a subpopulat
ion of LR-containing cells was found to express ERs. The extensive col
ocalization of receptors for leptin and estrogen in neuronal perikarya
of all parts of the hypothalamus suggests a closely coupled interacti
on between these peripheral signals in the regulation of a variety of
behavioral and neuroendocrine mechanisms. (C) 1998 Elsevier Science B.
V. All rights reserved.