Submitted to: Biochemical and Biophysical Research Communications
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/20/2003
Publication Date: 11/1/2003
Citation: Czaja, K., Kraeling, R.R., Barb, C.R. 2003. Are the hypothalamic neurons transsynaptically connected with the porcine adipose tissue. Biochemical and Biophysical Research Communications. 2003. v. 311. p. 482-485. Interpretive Summary: Adipose tissue is no longer considered as only a depot to store excess energy in the form of fat. Numerous biologically active substances, which affect appetite, growth and reproduction are produced by adipose tissue. Thus, adipose tissue can be viewed as an endocrine organ. The recently discovered protein, leptin, is secreted by fat tissue and serves as a circulating signal of nutritional status and regulates body weight, energy expenditure, growth and reproduction through a central nervous system (CNS) action, but specific anatomical sites and pathways responsible for mediating these effects are still unclear. In collaboration with scientists at the University of Warmia and Mazury in Olsztyn, Poland, ARS scientists at the Richard B. Russell Agricultural Research Center examined the possibility that leptin receptor-containing neurons in the porcine hypothalamus are transsynaptically connected to the perirenal fat tissue. Pseudorabies virus labeled neurons were found in various areas of the hypothalamus by nine days after injection of the virus into the perirenal fat tissue . Leptin receptors were present in nearly all virus-infected hypothalamic neurons. These are the first morphological data demonstrating a multisynaptic circuit of neurons of CNS origin which innervates porcine fat tissue. Therefore, understanding the specific anatomical sites and neural pathways by which leptin acts is the foundation for developing new methods to promote efficient growth and accelerate puberty.
Technical Abstract: Leptin, secreted by white adipocytes, has profound feeding, metabolic, and neuroendocrine effects. Leptin acts on the brain, but specific anatomical sites and pathways responsible for mediating these effects are still poorly understood, especially in breeding animals. Therefore, we examined the distribution of leptin receptor-containing neurons transsynaptically connected with the porcine perirenal fat tissue by means of a combined viral transneuronal tracing technique and immunohistochemical staining method. Pseudorabies virus (PRV), the retrograde transsynaptic tracer, was injected into the perirenal fat tissue in female pigs, and after survival periods of 3, 5, 7, 9 and 11 days, hypothalami were processed immunohistochemically with primary antisera against PRV and leptin receptor (OBR). PRV labeled neurons were found in paraventricular nucleus (PVN), ventromedial nucleus (VMN), anterior hypothalamic area (AHA), preoptic area (PA), arcuate nucleus (ARC), and supraoptic nucleus (SON) by nine days after injection of the virus. Double-labeling immunofluorescence demonstrated that OBR were co-localized in nearly all virus-infected hypothalamic neurons. The present results provide the first morphological data demonstrating a multisynaptic circuit of neurons of CNS origin which innervates porcine fat tissue.