Segmental analysis of neuropeptide concentrations in normal human spinal cord

We concurrently measured, by radioimmunoassay, levels of substance P (SP), somatostatin (SST), methionine-enkephalin (Met-Enk), cholecystokinin (CCK), peptide hystidyl-isoleucine (PHI), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in the ventral and dorsal gray matter at each segment of the cervical, thoracic, lumbar, and sacral spinal cord, obtained within 6 hours of death from 4 subjects (ages 17 to 55) with no neurologic disease. Levels (pmol/g gray matter) of SP, SST, and Met-Enk throughout and PHI, VIP, and NPY in lumbar and sacral cord were significantly higher in dorsal than in ventral gray matter. PHI, VIP, and NPY were significantly higher in lumbar and especially sacral cord than in cervical and thoracic segments. In rats, a postmortem delay of up to 8 hours did not affect SP, Met-Enk, PHI, or NPY and decreased SST, CCK, and VIP levels. Thus, there is a characteristic profile of neuropeptide distribution in gray matter, which emphasizes the neurochemical heterogeneity along the rostrocaudal and dorsoventral extent of normal human spinal cord.