Regional Distribution of Neurokinin A and Substance P in the Rat Central Nervous System

Substance P (SP) is a member of the tachykinin family of bioactive peptides including physalaemin, eledoisin and kassinin, and SP has putative physiological action in the CNS. In addition to SP, two novel tachykinins have recently been identified in mammalian CNS, namely neurokinin A (substance K, SK) and neurokinin B (1,2). There seem to be differences in the relative potencies of biological activities between the two naturally occurring mammalian tachykinins SP and SK in the peripheral systems. The biological activities of SK more closely resemble those of kassinin than of SP or physalaemin (3–6).