Electron microscope immunohistochemical localization of substance P in the central nervous system of the rat.

Substance P is an undecapeptide that is distributed in many areas of the central nervous system. In order to clearly identify the structures and organelles containing substance P, an immunohistochemical localization of this peptide was performed at the ultrastructural level. Substance P was detected in dense core vesicles of many nerve endings in both the amygdaloid nucleus and the substantia gelatinosa of the spinal cord. These findings support the hypothesis that substance P could act as a neurotransmitter.