Intake inhibition by NPY and CCK-8: A challenge of the notion of NPY as an "Orexigen".
We tested the hypothesis that neuropeptide Y (NPY) interacts with cholecystokinin octapeptide (CCK-8) in inhibition of intake of an intraorally infused solution of sucrose, a test of consummatory ingestive behavior. Both intracerebroventricular infusion of NPY (10 microg) and intraperitoneal injection of CCK-8 (0.5 micro/kg) reduced the intake of a 1M solution of sucrose infused intraorally at a rate of 0.5 ml/min in ovariectomized female rats, but the two peptides did not interact in inhibiting intraoral intake. By contrast, NPY increased intake if the sucrose solution was ingested from a bottle, a test demanding both appetitive and consummatory ingestive responses. CCK-8 inhibited intake in this test and its inhibitory effect was increased by simultaneous treatment with NPY. The activity in the nucleus of the solitary tract (NTS), a brainstem relay mediating inhibition of intake, judged by the expression of c-fos-like immunoreactivity, was significantly increased after treatment with CCK-8 or NPY to approximately the same extent. Combined treatment with NPY and CCK-8 did not increase the c-fos-like immunoreactivity in the NTS above treatment with NPY or CCK-8 alone. These results strengthen the hypothesis that NPY, like CCK-8, is an inhibitor of consummatory ingestive behavior and suggest that this inhibition is mediated via the NTS.
Ammar
A A
AA
Karolinska Institutet, Section of Applied Neuroendocrinology, Novum, S-14157 Huddinge, Sweden.
Nergårdh
R
R
Fredholm
B B
BB
Brodin
U
U
Södersten
P
P
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004347:Drug Interactions; D005247:Feeding Behavior / Q000187:drug effects*; D005260:Female; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D007266:Inhibition, Psychological; D009478:Neuropeptide Y / Q000494:pharmacology*; D010052:Ovariectomy / Q000379:methods; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012844:Sincalide / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism
D009478:Neuropeptide Y; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D012965:Sodium Chloride; D012844:Sincalide