Identification and cellular localisation of NPW 1 (GPR7) receptors for the novel neuropeptide W-23 by [ 125I]-NPW radioligand binding and immunocytochemistry

Abstract

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.