Li A-J, Dinh TT, Ritter S (2007) Destruction of NPY receptor expressing neurons in the arcuate nucleus causes obesity and hyperphagia without increasing lateral hypothalamic orexigenic peptide gene expression. Neuroscience 2007 Abstracts 524.20/BBB20. Society for Neuroscience, San Diego, CA.
Summary: NPY-SAP, a conjugate of neuropeptide Y (NPY) and the ribosomal inactivating toxin, saporin (SAP), is a compound that selectively lesions NPY receptor-expressing neurons. Previously we showed that injection of NPY-SAP into the hypothalamic arcuate nucleus (ARC) induces hyperphagia and obesity in rats. To further investigate the mechanisms responsible for NPY-SAP-induced obesity, we injected NPY-SAP or blank-saporin (B-SAP) control into the ARC and subsequently examined the expression of two orexigenic neuropeptide genes in the lateral hypothalamic area (LHA), which is densely innervated by ARC neurons. Our hypothesis was that loss of leptin-sensitive neurons in the ARC in the NPY-SAP injected rats would lead to increased expression of orexigenic neurons elsewhere in the hypothalamic feeding circuitry. Body weight gain and food intake were dramatically increased in the NPY-SAP group. In addition, expression of NPY and cocaine- and amphetamine-regulated transcript (CART) mRNA was significantly reduced in the ARC of obese rats, indicating a loss of NPY receptor-expressing NPY and CART neurons in this region. In contrast, NPY and CART gene expression in the dorsomedial hypothalamic nucleus was unchanged in NPY-SAP rats, indicating that the NPY-SAP-induced lesion was limited to the ARC. However, contrary to our hypothesis, expression of the orexigenic neuronpeptides, melanin-concentrating hormone (MCH) or prepro-orexin mRNA in LHA was not enhanced, but was slightly reduced in the NPY-SAP rats. These results indicate that an enhancement of MCH or orexin expression in the LHA is not necessary for the hyperphagia and obesity observed after NPY-SAP lesions in the ARC. Supported by PHS grant #DK 40498.
Related Products: NPY-SAP (Cat. #IT-28), Blank-SAP (Cat. #IT-21)