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Acute selective ablation of rat insulin promoter-expressing (RIPHER) neurons defines their orexigenic nature

Rother, Eva, Belgardt, Bengt F., Tsaousidou, Eva, Hampel, Brigitte, Waisman, Ari, Myers, Martin G., Brüning, Jens C.
Proceedings of the National Academy of Sciences of the United States of America 2012 v.109 no.44 pp. 18132-18137
body weight changes, energy, food intake, homeostasis, hypothalamus, insulin, islets of Langerhans, mice, models, neurons, pituitary gland, rats, transgenes
Rat insulin promoter (RIP)-expressing neurons in the hypothalamus control body weight and energy homeostasis. However, genetic approaches to study the role of these neurons have been limited by the fact that RIP expression is predominantly found in pancreatic β-cells, which impedes selective targeting of neurons. To define the function of hypothalamic RIP-expressing neurons, we set out to acutely and selectively eliminate them via diphtheria toxin-mediated ablation. Therefore, the diphtheria toxin receptor transgene was specifically expressed upon RIP-specific Cre recombination using a RIP-Cre line first described by Herrera (RIP HER-Cre) [Herrera PL (2000) Development 127:2317–2322]. Using proopiomelanocortin–expressing cells located in the arcuate nucleus of the hypothalamus and in the pituitary gland as a model, we established a unique protocol of intracerebroventricular application of diphtheria toxin to efficiently ablate hypothalamic cells with no concomitant effect on pituitary proopiomelanocortin–expressing corticotrophs in the mouse. Using this approach to ablate RIP HER neurons in the brain, but not in the pancreas, resulted in decreased food intake and loss of body weight and fat mass. In addition, ablation of RIP HER neurons caused increased c-Fos immunoreactivity of neurons in the paraventricular nucleus (PVN) of the hypothalamus. Moreover, transsynaptic tracing of RIP HER neurons revealed labeling of neurons located in the PVN and dorsomedial hypothalamic nucleus. Thus, our experiments indicate that RIP HER neurons inhibit anorexigenic neurons in the PVN, revealing a basic orexigenic nature of these cells.