NEUROTENSIN AND NEUROENDOCRINE REGULATION

More than two decades of research indicate that the peptide neurotensi n (NT) and its cognate receptors participate to a remarkable extent in the regulation of mammalian neuroendocrine systems, potentially at mu ltiple levels in a given system. NT-synthesizing neurons appear to exe rt a direct or indirect stimulatory influence on neurosecretory cells that synthesize gonadotropin-releasing hormone, dopamine (DA), somatos tatin, and corticotropin-releasing hormone (CRH). In addition, context -specific synthesis of NT occurs in hypothalamic neurosecretory cells located in the arcuate nucleus and parvocellular paraventricular nucle us, including distinct subsets of cells which release DA, CRH, or grow th hormone-releasing hormone into the hypophysial portal circulation. At the level of the anterior pituitary, NT stimulates secretion of pro lactin and occurs in subsets of gonadotropes and thyrotropes. Moreover , circulating hormones influence NT synthesis in the hypothalamus and anterior pituitary, raising the possibility that NT mediates certain f eedback effects of the hormones on neuroendocrine cells. Gonadal stero ids alter NT levels in the preoptic area, arcuate nucleus, and anterio r pituitary; adrenal steroids alter NT levels in the hypothalamic peri ventricular nucleus and arcuate nucleus; and thyroid hormones alter NT levels in the hypothalamus and anterior pituitary. Finally, clarifica tion of the specific neuroendocrine roles subserved by NT should be gr eatly facilitated by the use of newly developed agonists and antagonis ts of the peptide. (C) 1997 Academic Press.