Immunohistochemical localization of seven different peptides in the human spinal cord

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Abstract
It is necessary to study the normal chemical contents in the human spinal cord in order to understand neurochemical changes that might occur under pathological conditions. In the present study, the comparative distribution of seven peptides was examined immunohistochemically in four levels (cervical, C; thoracic, T; lumbar, L; sacral, S) of the human spinal cord by means of the peroxidase‐antiperoxidase technique. The peptides examined included bombesin (BOM), substance P (SP), cholecystokinin (CCK), somatostatin (SOM), methionine‐enkephalin (M‐ENK), vasoactive intestinal polypeptide (VIP), and thyrotropin releasing hormone (TRH). Among the seven peptides examined, four (BOM, CCK, SOM, and TRH) have never been described in the human spinal cord and the present work clearly demonstrates their existence in specific patterns. The terminals that were immunostained for BOM and CCK were localized in high concentration in the superficial dorsal horn (laminae I‐II), in moderate amounts in the lateral part of laminae V and VII, and lesser amounts in the intermediate gray (lamina VII) and the dorsal part of the central gray (lamina X). Whereas BOM showed a similar distribution pattern at all spinal levels, CCK was mainly found in thoracic and lumbar levels. The SOM terminals were localized in the superficial dorsal horn (the highest density in lamina II but very few in lamina I), the intermediolateral cell column, intermediate gray, and central gray. This peptide was more widely distributed in the sacral cord with its terminal field extending into the ventral horn. The TRH terminals were mainly located in the ventral horn. Frequently, TRH terminals were seen adjacent to large ventral horn neurons. Furthermore, many neurons in the ventral and intermediate gray and Clarke's column demonstrated TRH immunoreactivity. The other three peptides (SP, M‐ENK, and VIP) have been previously demonstrated in the human spinal cord and the present study confirmed their general spinal distribution with minor differences.