Binding profile of benextramine at neuropeptide Y receptor subtypes in rat brain areas

Binding studies in rat whole brain, frontoparietal cortex and brainstem membrane preparations revealed that benextramine displaced [3H]neuropeptide Y specific binding from a low and a high affinity site with IC50 values in the microM (36 +/- 2, 4.4 +/- 1.4 and 300 +/- 120 microM, respectively) and the pM (29.3 +/- 12.1, 0.35 +/- 0.11 and 0.42 +/- 0.03 pM, respectively) range, whereas in rat hippocampus benextramine displaced [3H]neuropeptide Y specific binding from one site only with an IC50 value of 22.8 +/- 5.7 microM. With the exception of frontoparietal cortex binding assay, benextramine was not able to completely inhibit [3H]neuropeptide Y specific binding revealing the presence of a benextramine nonsensitive third binding site. Benextramine pretreatment followed by membrane washing demonstrated that benextramine inhibited irreversibly both high and low affinity sites.