Localization of nocistatin-binding sites in mice brain and spinal cord using a biotinylated nocistatin probe

Nocistatin and nociceptin/orphanin FQ are two neuropeptides processed from the same precursor prepronociceptin. They have opposing roles in nociception and several other biological functions. Whereas the location and structure of the nociceptin/orphanin FQ receptors has been defined, the location of the nocistatin receptors remains unknown. In the course of this study, we synthesized a novel probe for histochemistry by linking biotin to the N terminus of nocistatin, and purified this with high-pressure liquid chromatography and confirmed the structure by mass spectrometer. Using this probe, we found nocistatin-binding sites in the cerebral cortex and the dorsal horn nucleus of the spinal cord. We also found that the nocistatin-binding sites were in the cell body, whereas the nociceptin/orphanin FQ binding sites were on the fibrous processes.