Submitted to: Neuroscience Letters
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/2/2007
Publication Date: 9/20/2007
Citation: Czaja, K., Barb, C.R., Kraeling, R.R. 2007. Leptin receptor (obr) containing hypothalamic neurons projecting to different adipose tissue depots in the pig. Neuroscience Letters. V. 425(1):6-11, 2007. Interpretive Summary: The recently discovered protein, leptin, secreted by fat cells in response to changes in body weight or energy, stimulates metabolism, regulates appetite and LH secretion, pituitary hormone necessary for reproduction. Leptin may serve as a signal linking the body's energy regulating system with the reproductive system. This is the first report to demonstrate that leptin receptors (OBR) have been found in brain hypothalamic neurons that regulate appetite and the release of LH from the pituitary, with projections from the to the adipose tissue. These results provide the morphological data on a regulatory circuit of neurons innervating adipose tissue that are involved in regulating reproduction in the pig. Therefore, understanding the leptin – brain-LH interactions is necessary in order to develop new methods to accelerate puberty and improved reproductive efficiency in the breeding herd.
Technical Abstract: The purpose of the study was to establish whether or not leptin receptors (OBR)-containing hypothalamic neurons are transsynaptically connected to the adipose tissue depots in the pig. Pseudorabies virus (PRV, Bartha’s K strain) was introduced in perirenal or subcutaneous adipose tissue depots in crossbred gilts. After survival periods of 9, 11 and 13 days hypothalami were dissected and processed immunohistochemically with primary antisera against PRV and OBR. PRV infected neurons localized in paraventricular nucleus (PVN), supraoptic nucleus (SON) and arcuate nucleus (ARC) were found after injections into both the perirenal and the subcutaneous adipose tissue depots. Ventromedial nucleus (VMN), dorsomedial nucleus (DMN) and preoptic area (PA) infected neurons were found after injection of PRV into perirenal adipose tissue, while infected cells in lateral hypothalamic area (LHA) projected only to the subcutaneous adipose tissue. Almost all PRV infected neurons expressed OBR-immunoreactivity. The present results provide the morphological data on the multisynaptic circuit of neurons innervating adipose tissue in the pig and demonstrate that hypothalamic nuclei involved in reproductive processes are transsynaptically connected to the perirenal and subcutaneous adipose tissue depots.