AJP - Endocrinology and Metabolism, Vol 260, Issue 6 E839-E845, Copyright © 1991 by American Physiological Society
Specific neuropeptide Y binding sites in chicken brain
M. L. Adamo and R. L. Hazelwood
Department of Biology, University of Houston, Texas 77204-5513.
In the present study, 125I-labeled neuropeptide Y (NPY) binding to chicken
brain regions was evaluated. Cerebellum and cerebral cortex membranes bound
significantly more 125I-NPY specifically than did membranes from other
brain regions. Scatchard plots of NPY binding to cerebellar membranes were
curvilinear; the high-affinity component had an affinity (Kd) of 1.1 nM,
with a receptor concentration (Ro) of 182 fmol/mg membrane protein.
Scatchard plots of NPY binding to chicken cerebral cortex membranes were
linear, with a Kd of 0.63 nM and Ro of 90 fmol/mg. Unlabeled avian
pancreatic polypeptide (APP) inhibited 125I-NPY binding to cerebellar
membranes with a constant at which 50% inhibition occurs of 0.5 nM but
showed essentially no affinity for cerebral cortex NPY binding sites. As
previously reported, 125I-APP bound to cerebellar membranes with a Kd of
0.365 nM and an Ro of 323 fmol/mg, and unlabeled NPY showed about one order
of magnitude lower affinity than did unlabeled APP for 125I-APP binding
sites. Pseudo-Hill coefficients for APP binding to cerebellar APP receptors
and NPY binding to cerebellar NPY receptors were 0.9. In contrast,
pseudo-Hill plots for APP competition for 125I-NPY binding were
curvilinear. It is concluded that the chicken cerebellum contains distinct
APP and NPY receptors, whereas cerebral cortex contains only NPY receptors.
APP is capable of binding with high affinity to the cerebellar, but not the
cortical, NPY receptor.
