NEUROPEPTIDE-Y RECEPTORS FROM CALF BRAIN - EFFECT OF CRUDE CONUS VENOM PREPARATIONS ON [H-3] NPY BINDING

NPY receptors are identified in calf frontal cortex and hippocampus me mbrane preparations by binding of N-[propionyl-H-3] neuropeptide Y. Sa turation and competition binding data with PYY, NPY-18-36) and NPY its elf fit with a single class of sites: for the radioligand K-D=1.4+/-0. 5 nM, B-max=434+/-180 fmol/mg protein in frontal cortex, K-D=0.7+/-0.2 nM, B-max=267+/-50 fmol/mg protein in hippocampus. Competition curves of the Y-1-subtype selective agonist [Leu(31), Pro(34)]NPY are biphas ic in both membrane preparations: high affinity sites (i.e. Y-1-subtyp e) amount to 80% in frontal cortex and 23% in hippocampus. The remaini ng sites are of the Y-2-subtype. Out of 23 Conus venom preparations, 1 7 inhibit the binding of [H-3]NPY in both membrane preparations, but o nly two of them (from Conus aulicus and C. pennaceus) do so with high potency (IC50<5 mu g protein/ml). Only one venom preparation (from C. mercator) had weak discriminatory properties (IC50Y2/IC50Y1=6) Venom f rom C. anemone increased the [H-3]NPY binding 5-fold and with an IC50 of 15-18 mu g protein/ml. This binding occurred to the venom itself an d was unrelated to the NPY receptors since it was equally potent when displaced by [Leu(31), Pro(34)]NPY, NPY-(18-36), PW and NPY. Copyright (C) 1996 Elsevier Science Ltd