Research reportMicroinjection of RFRP-1 in the central nucleus of amygdala decreases food intake in the rat

Several members of the RFamide peptide family are known to have role in the regulation of feeding. For example, neuropeptide FF and prolactin-releasing peptide cause anorexigenic, while 26RFa and QRFP result in orexigenic effects in rodents. I.c.v. microinjection of neuropeptide RFRP-1 significantly reduced food and water intake in chicks. However, feeding related effects of RFRP-1 have not been studied in mammals yet. The central part of amygdala (CeA) is essentially involved in the regulation of feeding and body weight. RFRP-1 positive nerve cells were detected in the rat hypothalamus and RFRP-1 immunoreactive fibers were identified in the CeA. RFRP analogs bind with relatively high affinity to the NPFF1 and NPFF2 receptors (NPFF-R). RFRP-1 has potent activity for NPFF1. Significant expression of NPFF1 was detected in the CeA. To evaluate the role of RFRP-1 in feeding regulation rats were microinjected with different doses of RFRP-1 and their food intake were quantified over a 60 min period. Liquid food intake of male Wistar rats was measured after bilateral intraamygdaloid administration of RFRP-1 (25, 50 or 100 ng/side, RFRP-1 dissolved in 0.15 M sterile NaCl/0.4 μl, respectively). The 50 ng dose of RFRP-1 microinjections resulted in significant decrease of food intake. The 25 and 100 ng had no effect. Action of 50 ng (37.8 pmol) RFRP-1 was eliminated by 20 ng (41.4 pmol) RF9 NPFF-R antagonist pretreatment. In open-field test 50 ng RFRP-1 did not modify spontaneous locomotor activity and general behavior of animals did not change. Our results are the first reporting that RFRP-1 injected to the CeA result in a decrease of liquid food consumption. This is a receptor-linked effect because it was eliminated by a NPFF-R selective antagonist.

► RFRP-1 belonging to the RFamide peptide family was microinjected to the amygdala. ► RFRP-1 in 50 ng dose decreases liquid food intake in rats. ► NPFF receptor antagonist RF9 pretreatment prevents RFRP-1 effect in the amygdala. ► These results are the first to show feeding related effects of RFRP-1 in mammals.