Neuropeptide Y induced feeding in the rat is mediated by a novel receptor.
There are now six recognized neuropeptide Y (NPY) receptor subtypes (Y1-Y4 and two recently cloned distinct receptors labeled Y5), of which Y1 and one of the Y5's have been suggested could mediate the effect of NPY on feeding. The fragments NPY(2-36) and NPY(3-36), which bind Y1 only poorly, were injected intracerebroventricularly (icv) and found to have similar dose-response relationships to NPY in the stimulation of feeding. However NPY (13-36), which stimulates both Y2 and Y5, caused no increase in food intake, even at high doses. Maximal stimulation with the classical Y1 agonist [Pro34]-NPY produced only 50% of the maximum effect of NPY itself despite fully inhibiting adenylyl cyclase activity in vitro in a Y1 system. The novel fragment [Pro34]-NPY(3-36) is as effective at stimulating food intake as the classical Y1 analogue [Pro34]-NPY but bound to the Y1 receptor with only 1/20th of the affinity of NPY and failed to inhibit adenylyl cyclase through this receptor. [Pro34]-NPY(3-36) is therefore a relatively appetite-selective ligand. Coadministration of high dose NPY(13-36) and [Pro34]NPY did not enhance feeding compared with [Pro34]-NPY alone. In addition, the NPY Y1 receptor antagonist BIBP-3226, which does not bind Y2, Y4, or Y5 receptors, significantly reduced NPY induced feeding. These results indicate that the feeding effect of icv NPY involves a novel receptor and that it is functionally distinct from the recognized receptor subtypes.
O'Shea
D
D
Department of Medicine, Hammersmith Hospital, Royal Postgraduate Medical School, London, United Kingdom.
Morgan
D G
DG
Meeran
K
K
Edwards
C M
CM
Turton
M D
MD
Choi
S J
SJ
Heath
M M
MM
Gunn
I
I
Taylor
G M
GM
Howard
J K
JK
Bloom
C I
CI
Small
C J
CJ
Haddo
O
O
Ma
J J
JJ
Callinan
W
W
Smith
D M
DM
Ghatei
M A
MA
Bloom
S R
SR
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004435:Eating / Q000187:drug effects*; D008297:Male; D009478:Neuropeptide Y / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017476:Receptors, Neuropeptide Y / Q000502:physiology*
D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; D000262:Adenylyl Cyclases