Identification and cellular localisation of NPW1 (GPR7) receptors for the novel neuropeptide W-23 by [125I]-NPW radioligand binding and immunocytochemistry.

Using a novel radioligand, we have identified high-affinity binding sites (K(D)=0.44+/-0.13 nM) for the recently discovered peptide, neuropeptide W (NPW), in rat brain. Binding density was highest in the amygdala (B(max)=149.9+/-13.8 fmol/mg protein), thalamic, and hypothalamic nuclei. A similar distribution was observed in mouse brain. We have confirmed the identity of these binding sites as the G-protein-coupled receptor, NPW(1) (previously designated orphan receptor GPR7), using site-directed antisera that revealed receptors were expressed by neuronal cell bodies and processes. Additionally, we have demonstrated the presence of NPW-like immunoreactivity in neuronal cell bodies in areas projecting to the amygdala, such as the dorsal raphe nucleus and ventral tegmental area, providing evidence for an emerging new transmitter system.