Estrogen-regulated synthesis of neurotensin in neurosecretory cells of the hypothalamic arcuate nucleus in the female rat

Neurotensin (NT) is implicated as a neurohormone in mammals, yet the peptide's neuroendocrine role remains to be determined. NT immunoreactivity has been observed in neurosecretory cells of the arcuate nucleus and paraventricular nucleus, and data suggest that NT release into hypophysial portal blood mediates a component of PRL secretion that is female specific and dependent on ovarian steroids. In the present study, in situ hybridization histochemistry and immunohistochemistry were used to investigate the regulation of NT gene expression in hypothalamic neurosecretory regions of adult rats. In ovariectomized females, estradiol induced expression of messenger RNA (mRNA) encoding NT and neuromedin N (NT/N mRNA) in the dorsomedial division of the arcuate nucleus. In contrast, estradiol did not appreciably alter NT/N mRNA expression in the ventrolateral division of the arcuate nucleus, where labeled cells were numerous, or in the paraventricular nucleus, where labeled cells were virtually absent. Estradiol a...