Regional distribution of substance P, neurokinin alpha and neurokinin beta in rat central nervous system.

Recently, we have found novel mammalian tachykinins, neurokinin alpha and beta isolated from porcine spinal cord, whose chemical structures are similar to those of substance P or kassinin. In the present study, we describe a specific assay system for neurokinin alpha and beta by combining HPLC and radioimmunoassay. We investigated the regional distribution of tachykinins including substance P in the rat central nervous system using anti-neurokinin alpha antiserum which cross-reacts 25% with neurokinin beta. As a result, it is noted that substance P was the highest in concentration in the rat substantia nigra, the striatum, the cerebellum and the spinal cord, but not in the cerebral cortex in which neurokinin beta was the highest. Concentration of neurokinin alpha was lower than that of substance P and the molar ratio of substance P and neurokinin alpha was fairly constant (2.8-4.0) in all regions. On the other hand, it is noted that the molar ratio of substance P and neurokinin beta was extremely variable and seemed to be specific to tissues.