Possible role of neuropeptide Y in experimental cancer anorexia.

The efficacy of NPY to elicit feeding in TB rats was reduced prior to the onset of overt anorexia, with the feeding response decreasing further as anorexia developed. Hypothalamic concentration of NPY was reduced in TB rats, with the magnitude of the decrease paralleling the degree of anorexia. Binding affinity of NPY to hypothalamic membranes taken from TB rats suggested decreased binding affinity with no change in receptor number. Infusing ammonium salts at a concentration and rate necessary to increase blood ammonia levels to the degree observed in TB rats, produced anorexia and decreased NPY feeding. These results suggest that NPY feeding systems are abnormal in TB rats and that hyperammonemia may be of primary importance in this dysfunction.