Regulation of neuropeptide Y (NPY) binding by guanine nucleotides in the rat cerebral cortex

In the presence of GTP, GDP, GMPP(NH)P, GMPP(CH2)P, GMPP(S)P but not in the presence of GMP, cGMP or ATP, the high affinity binding of neuropeptide Y (NPY) was reduced in a dose-dependent manner. GTP (0.1 mM) diminished the maximal binding capacity for 125I-labelled NPY by 40% without any change in the equilibrium dissociation constant of the receptor 125I-labelled NPY complex.