Tachykinin NK3 receptor (NK3R) is a g-protein coupled receptor that is heavily expressed by magnocellular neurons of the paraventricular nucleus of the hypothalamus (PVN). Osmotic challenge is reported to activate NK3R expressed by magnocellular neurons and cause the NK3R to be internalized to the cytoplasm and perhaps the cell nucleus. In this study we show using immunoelectron microscopy that isolated nuclei from neurons in the PVN of osmotic challenged animals show a robust labeling for the NK3R. NK3R immunoreactivity was detected by Western blot in isolated nuclei of PVN neurons following the 2 M NaCl injection. No nuclear NK3R immunoreactivity was detected in control animals. NK3R antibody specificity was confirmed by small interfering (SI) RNA technology. This study establishes that the NK3R is trafficked to the nucleus of PVN neurons following a peripheral osmotic challenge.
KeywordsG-protein coupled receptor; Cell signaling; Electron microscopy; siRNA Magnocellular neurons of the hypothalamus synthesize and secrete two key hormones: vasopressin (VP) and oxytocin (OT). The release of these hormones is influenced by a number of transmitters and magnocellular neurons express a number of receptors. Noteworthy is the tachykinin, NK3 receptor (NK3R) which is heavily expressed by magnocellular neurons of the supraoptic (SON) and paraventricular nucleus (PVN) of the hypothalamus (Ding et al., 1999). NK3R expressed by magnocellular neurons appears to have a functional role in the release of vasopressin and oxytocin. Stimulation of NK3R results in an increase in Ca ++ conductance (Buell et al., 1992), induction of c-Fos expression in magnocellular neurons, and causes the systemic release of both hormones (Ding et al., 1999;Smith and Flynn, 2000;Bealer and Flynn, 2003). Furthermore, the release of the endogenous ligand, presumably neurokinin B (NKB), and binding to the NK3R results in the internalization of the peptide-receptor complex (Chawala et al., 1997;Colin et al., 2002;Lessard et al., 2004;Johnson et al., 2004) that can be tracked immunohistochemically. NK3R expressed by magnocellular neurons are membrane bound in control (isotonic saline treated) animals. After hyperosmotic or Direct correspondence to: Francis W. Flynn, 1000 E. University Ave., Dept 3166, Laramie, WY 82071, tel: 307-766-6446, e-mail: flynn@uwyo.edu. Section Editor: Dr. Miles Herkenham Systems Neuroscience, Bethesda, MD, USA Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
NIH Public Access
Author ManuscriptNeuroscience. Author manuscript; available in PMC 2009 July 31.
Published in final edi...