Lasting loss in substance P following administration of substance P antiserum to newborn rats. An immunohistochemical study.

Substance P (SP) antiserum (500 micrograms protein) was administered to rats on the second day of life and the animals were sacrificed 3 months later. This treatment produced a loss in SP immunoreactive fibers in the dorsal horn of the spinal cord, in the substantia nigra and in the periaqueductal gray matter, when compared to control animals receiving a neonatal treatment of non-specific immunoglobulins. In the dorsal horn, the observed depletion was greater in the superficial layers, lamina I and lamina IIo. Immunoreactivity for Met-enkephalin was apparently unchanged by SP antiserum. Results of this study provide cytochemical evidence for a specific and lasting deleterious effect of SP antiserum on different SP-containing neuronal systems.