Dinh TT, Smith BR, Wiater MF, Jansen H, Li A-J, Ritter S (2011) Lesions targeting leptin-sensitive neurons in the ventromedial and suprachiasmatic nuclei differentiate sites for circadian control of feeding. Neuroscience 2011 Abstracts 600.13. Society for Neuroscience, Washington, DC.
Summary: We have previously investigated the role of leptin sensitive networks in the mediobasal hypothalamus (MBH) for feeding using the saporin toxin conjugated to leptin (Lep-SAP) and a control conjugate, blank-saporin (B-SAP). Lep-SAP binds to, is internalized by and destroys leptin receptor expressing neurons at the injection site. We found that injections of Lep-SAP directed at the arcuate nuclei (Arc) caused profound regulatory and circadian deficits including arrhythmia for feeding. We have proposed that leptin-sensitive circuitry within the MBH, particularly the arcuate nuclei (Arc), is required for the maintenance of feeding rhythms. Here we tested this hypothesis further by examining effects of Lep-SAP injections into two additional hypothalamic nuclei in the vicinity of the Arc, the ventromedial nucleus (VMN) and the suprachiasmatic nucleus (SCN). In an additional group, the SCN was lesioned electrolytically. Feeding data were collected using BioDAQ computerized meal monitors (Research Diets, Inc) and analyzed using ClockLab software to generate double raster eatogram plots. Lomb-Scargle periodograms were used to assess rhythms and their robustness. Feeding was monitored under light:dark (LD) and dark:dark (DD) conditions in all groups except SCN Lep-SAPs. Unlike Arc-directed injections of Lep-SAP, VMN injections did not alter the diurnal distribution of feeding in either LD or DD and lesioned rats did not become obese or hyperphagic. Lomb-Scargle analysis and eatograms indicated that VMN rats have intact circadian rhythms for feeding. Both Lep-SAP and electrolytic lesions of the SCN caused a slight reduction body weight, compared to controls. Total 24h food intake was unchanged, but light-period food intake was increased. Rats with electrolytic lesions of the SCN were arrhythmic for feeding under both LD and DD conditions. Together with results from Arc Lep-SAP injections, these findings strongly implicate leptin-sensitive circuitry in the MBH in control of circadian feeding rhythms. In addition, they point to the particular significance of the Arc and its connections with the SCN in this circuitry. Leptin-sensitive neurons in the VMN appear to be of less importance in this role.
Related Products: Leptin-SAP (Cat. #IT-47)