Distribution of secretoneurin-like immunoreactivity in comparison with that of substance P in the human spinal cord.

Secretoneurin (SN), a neuropeptide of 33 amino acids, was determined in comparison with substance P (SP) by immunocytochemistry in normal human spinal cord. The density of secretoneurin-like immunoreactivity (SN-IR) was high in the superficial dorsal horn and in the lateral column of autonomic arcs. The ventral horn displayed low to moderate density of SN-IR and prominently outlined motoneurons. The congruent distribution of SN and SP to the termination of primary afferents may indicate that SN is involved in modulation of pain.