A Comparison of the Binding of [3H]Proprionyl-Neuropeptide Y to Rat and Human Frontal Cortical Membranes

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Abstract
The binding characteristics of [3H]proprionyl-neuropeptide Y ([3H]proprionyl-NPY) were studied in frontal cortical membranes prepared from rat and human postmortem tissue. The specific binding of NPY decreased as the magnesium concentration increased from 1.05 to 10 mM. The binding was also influenced by the concentration of GTP in the buffer medium, with a resulting 45% decrease in NPY binding in the presence of 10-6 M GTP. Using equilibrium binding studies, [3H]proprionyl-NPY was found to bind in both tissues with high affinity to a single class of receptors with a similar KD (0.035 nM). However, kinetic experiments in both tissues provided evidence for two components of [3H]proprionyl-NPY binding which may be related to receptor states. Competition binding experiments showed that peptide YY (PYY) was equal to NPY in its ability to displace [3H]proprionyl-NPY, whereas rat and human pancreatic polypeptide were without effect up to a concentration of 10-6 M. This suggests that, whereas PYY and NPY may compete for the same receptor(s), the pancreatic polypeptides probably act on a separate population of receptors.