Neuropeptide B (NPB) and neuropeptide W (NPW) are members of a recently identified neuropeptide family that are ligands for two highly similar receptors NPBW1 and NPBW2, both of which are coupled to Gi/o protein to inhibit intracellular cAMP production. Highest expression of NPBW1 mRNA and protein was identified in the amygdala and hypothalamic nuclei. Physiological studies demonstrate that intracerebroventricular infusion of NPBW1 ligands modulates feeding behavior, regulates the release of corticosterone, prolactin and growth hormone while also modulating pain pathway (Singh and Davenport, 2006). NPBW1 knock out male mice have shown mild adult-onset obesity and decreased locomotor activity. They become progressively hyperglycaemic and hyperinsulinaemic (Ishii et al., 2003). NPBW1 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 NPBW1 receptor interactions with its ligand. The membrane preparations exhibit a Kd of 0.53 nM for [125I]-Neuropeptide W23. With 5 ug/well of NPBW1 Membrane Prep and 0.35 nM [125I]-Neuropeptide W23, a greater than 10-fold signal-to-background ratio was obtained.