Aims: 

RFRP-3 is a member of the RF-amide peptide family. Some members of the RF-amide family are associated with satiety in rodents. I.C.V. injection of RFRP-3, however, facilitates feeding. It is well known, that the amygdala plays an important role in the regulation of food intake and body weight. RFRP-3-positive nerve cells were detected in the rat hypothalamus and RFRP-3 immunreactive fibers were identified in the central amygdaloid nucleus (CeA) by immunohistochemical analyses. RFRP analoguesbind with relatively high affinity to the NPFF1 and NPFF2 receptors (NPFF-R). RFRP-3 has potent activity for NPFF-1 that is expressed in the CeA. In the present experiments feeding related effects of RFRP-3 were studied in the CeA.

Methods: 

Male Wistar ratswere microinjected by different doses of RFRP-3 and their food intake were quantified over a 60 min period. Liquid food intake (milk, 136.45 kJ/100 ml Milk Quick) was measured after bilateral intraamygdalar administration of RFRP-3 (25, 50, 100, 200 ng/side, respectively). An application of 25 ng NPFF-R antagonist was carried out 15 min prior to 50 ng RFRP-3 microinjections. Fifty nanogramms NPFF-R antagonist was applied alone or 15 min prior to 100 ng RFRP-3 microinjections. Drugs were dissolved in sterile saline (0.15 M) and were microinjected bilaterally into the CeA in 0.4 ul.

Results: 

In ad libitum fed rats the 50 ng and 100 ng dose of RFRP-3 microinjections resulted in significant decrease in food intake. The 25 and 200 ng had no effect. Food intake decreasing effect of RFRP-3 was eliminated by prior ANT treatment. ANT applied in itself had no influence on feeding.

Conclusion: 

Our results are the first reporting that RFRP-3 injected to CeA resulted in a decrease of liquid food consumption. This is a receptor-linked effect because it was eliminated by a NPFF- R selective antagonist.

Support: 

NKTH-OTKA K68431 and by the HAS