Positive reinforcing effects of RFamide-related peptide-1 in the rat central nucleus of amygdala.

The amygdaloid body (AMY) plays an important role in memory, learning and reward-related processes. RFamide-related peptide-1 (RFRP-1) immunoreactive fibers and NPFF1 receptors were identified in the AMY, and previously we verified that neuropeptide RFRP-1 infused into the central nucleus of AMY (CeA) caused food intake decrease. The aim of the present study was to examine the possible rewarding or aversive effects of RFRP-1 in the CeA. In conditioned place preference, test male Wistar rats were microinjected bilaterally with 50 or 100ng RFRP-1 in volume of 0.4μl. In other groups of animals, 20ng NPFF receptor antagonist RF9 was applied or the antagonist was used 15min before 50ng RFRP-1 treatment. Fifty nanograms of RFRP-1 had positive reinforcing properties, while 100ng RFRP-1 had no effect. Prior treatment with NPFF receptor antagonist RF9 could block the rewarding effects of RFRP-1, while the antagonist applied alone did not influence the behavior of rats in place preference paradigm. Our results show that RFRP-1 and NPFF-1 receptors play important roles in the amygdaloid rewarding-reinforcing mechanisms.