Identification and quantification of neuropeptides in naïve mouse spinal cord using mass spectrometry reveals [des-Ser1]-cerebellin as a novel modulator of nociception

Abstract

Neuropeptide transmitters involved in nociceptive processes are more likely to be expressed in the dorsal than the ventral horn of the spinal cord. This study was designed to examine the relative distribution of neuropeptides between the dorsal and ventral spinal cord in naïve mice using liquid chromatography, high-resolution mass spectrometry. We identified and relatively quantified 36 well-characterized full-length neuropeptides and an additional 168 not previously characterized peptides. By extraction with organic solvents we identified seven additional full-length neuropeptides. The peptide [des-Ser1]-cerebellin (desCER), originating from cerebellin precursor protein 1 (CBLN1), was predominantly expressed in the dorsal horn. Immunohistochemistry showed the presence of CBLN1 immunoreactivity with a punctate cytoplasmic pattern in neuronal cell bodies throughout the spinal gray matter. The signal was stronger in the dorsal compared to the ventral horn, with most CBLN1 positive cells present in outer laminae II/III, colocalizing with calbindin, a marker for excitatory interneurons. Intrathecal injection of desCER induced a dose-dependent mechanical hypersensitivity but not heat or cold hypersensitivity. This study provides evidence for involvement of desCER in nociception and provides a platform for continued exploration of involvement of novel neuropeptides in the regulation of nociceptive transmission. Neuropeptides involved in nociceptive processes are more likely to be expressed in the dorsal than the ventral horn of spinal cord. Well-characterized full-length neuropeptides as well as uncharacterized neuropeptides were quantified by mass spectrometry. The CBLN1-derived peptide [des-Ser1]-cerebellin (desCER) is predominantly expressed in the dorsal horn, and intrathecal injection of desCER induced a dose-dependent mechanical hypersensitivity.

Keywords: mass spectrometry; neuropeptides; nociception; pain; peptidomics; spinal cord.