[Chemical neuroanatomy of the human spinal cord]

Modern neuroanatomical methods, specifically immunocytochemistry and receptor autoradiography, have greatly increased our knowledge on the organization of the human nervous system. This review, based on the literature and largely on personal results, is devoted to the chemical neuroanatomy of the normal human spinal cord. It provides a comprehensive overview of the differential distribution of various chemical messengers, their metabolizing enzymes and their receptors (acetylcholine, amino acids, monoamines, neuropeptides) in the neuronal laminae of the spinal gray matter. At the level of the dorsal horn, lamina II, i.e. Rolando's substantia gelatinosa, is characterized by a heavy concentration of several transmitters and receptors. Within the intermediate gray matter the autonomic nuclei receive a dense peptidergic input, e.g. substance P, enkephalin and VIP afferents. In the ventral horn close contacts are numerous between serotonergic or peptidergic (SP, TRH, enkephalins...) fibers and motoneuronal perikarya or dendrites. The present knowledge on the putative role of certain neurotransmitters in spinal functions is summarized.