Effect of capsaicin administration to neonatal rats on the substance P content of discrete CNS regions.

Substance P (SP) levels were determined by radioimmunoassay in microdissected CNS regions of adult animals treated with capsaicin as neonates and of vehicle controls. Capsaicin treatment reduced the SP content of the spinal trigeminal nucleus and the dorsal horn of the spinal cord whereas it had no effect on the SP levels in the ventral horn of the spinal cord, the nucleus tractus solitarius or in midbrain and forebrain areas analyzed.