Neuropeptide B (NPB) and neuropeptide W (NPW) are members of a recently identified neuropeptide family that are ligands for NPBW1 and NPBW2 receptors, both of which are coupled to Gi/o protein to inhibit intracellular cAMP production and share 64% sequence homology (Singh and Davenport, 2006). NPBW1 recognizes both NPB and NPW with similar nanomolar affinities (with a slight preference for NPB), whereas NPBW2 is moderately selective for NPW (Tanaka et al., 2003). NPBW2 is one of a few GPCRs that have no rat or mouse orthologue, although gene encoding NPBW2 has been discovered in other mammalian species such as rabbit (Lee et al., 1999). NPBW2 mRNA is known to be expressed in the frontal cortex, parietal cortex hippocampus, caudate nucleus, thalamus, pituitary, adrenal gland, and lymph node (Brezillon et al., 2003). Functions of NPBW2 may be involved in feeding, weight regulation, and pain response through direct or indirect actions in the central nervous system. NPBW2 membrane preparations are crude membrane preparations made from our proprietary stable recombinant cell lines to ensure high-level of GPCR surface expression; thus, they are ideal HTS tools for screening of antagonists of NPBW2 receptor interactions with its ligand. The membrane preparations exhibit a Kd of 2 nM for [125I]-Neuropeptide W23. With 10 ug/well of NPBW2 Membrane Prep and 0.35 nM [125I]-Neuropeptide W23, a greater than 10-fold signal-to-background ratio was obtained.