Neurotensin Neurons in the Rat Hypothalamus: An Immunocytochemical Study*

Abstract

Neurotensin was localized in the hypothalamic tissues of adult Sprague-Dawley rats by immunoperoxidase techniques. Visualization of perikarya was greatly enhanced by intraventricular administration of colchicine. Many perikarya containing neurotensin-like immunoreactivity were seen in the medial preoptic area, the periventricular hypothalamus, the parvocellular portion of the paraventricular nucleus, the arcuate nucleus, and the lateral hypothalamus in the perifornical area. There were moderate numbers of cell bodies in the ventral portion of the anterior hypothalamus, the dorsomedial nucleus, and the posterior hypothalamus. No positive cells were seen in the suprachiasmatic, ventromedial, or mammillary nuclei. Reactive fibers were generally distributed in the same regions as cell bodies. Additional dense collections were seen in the lateral part of the zona externa of the median eminence, the pituitary stalk, the posterior mammillary nucleus, and the most lateral portions of the hypothalamus at the medial edge of the crura cerbri. There were smaller numbers of fibers found in the pre-mammillary and posterior hypothalamic nuclei and the posterior pituitary gland. These results indicate that the neurotensin system in the hypothalamus is very extensive and complex, as it is in many other brain regions. Neurons and fibers are found in many hypothalamic areas, including projections to the hypophysial portal system in the median eminence, suggesting that neurotensin may affect neuroendocrine mechanisms at several levels, including the anterior pituitary gland.

Distribution of neurotensin/neuromedin N mRNA in rat forebrain: unexpected abundance in hippocampus and subiculum.

“…Labeling was conspicuously absent from the hypothalamic paraventricular nucleus and the adjacent periventricular region, areas previously reported to contain NTimmunoreactive cell bodies (8,18). One possible explanation for these results is that the content of NT/N mRNA in cells of these regions may be below the limits of detectability by in situ hybridization.…”

“…There was little, if any, signal associated with the paraventricular nucleus or the periventricular region, which was surprising because NT-immunoreactive cell bodies have been seen consistently in these areas (8,18). Labeled cells were observed in the arcuate nucleus, dorsomedial nucleus, and perifornical region, whereas the ventromedial nucleus was devoid of any labeling.…”

“…5, lanes 3-6). The central amygdala was chosen for comparison because it contains many NT-immunoreactive neurons (8,18) and because it exhibited dense labeling after in situ hybridization with the RNA probe (Fig. 2C).…”

“…The distribution of NT in the rat forebrain has been extensively mapped with immunocytochemical techniques (8,9,(15)(16)(17)(18)(19)(20)(21)(22)(23). DNA sequence analysis of cDNA and genomic clones has revealed that NT is synthesized as part of a larger precursor protein that also contains a coding domain for the NT-like peptide neuromedin N (2, 3).…”

Anorexigenic Hormones Leptin, Insulin, and α-Melanocyte-Stimulating Hormone Directly Induce Neurotensin (NT) Gene Expression in Novel NT-Expressing Cell Models

“…Both POMC/CART-and NPY/AgRP-containing neurons, in turn, project to other hypothalamic regions, including VMH, DMH, LHA, and the paraventricular nucleus (PVN) to regulate food intake and energy balance (Chiesi et al, 2001;Barsh and Schwartz, 2002;Berthoud, 2002;Funahashi et al, 2003). In the rat hypothalamus, NT neurons are widely distributed in the ARC, PVN, DMH, and LHA as immunocytochemistry studies have revealed (Kahn et al, 1980;Ibata et al, 1984). Leptin receptors (ObR b ) are also widely distributed in the ARC, PVN, and LHA (Mercer et al, 1996;Hakansson et al, 1998;Baskin et al, 1999a,b;Elmquist et al, 1999).…”