Influence of Anesthesia and Atropine on Plasma Extravasation Induced by Mammalian Tachykinins in the Rat

Until the recent discovery of two decapeptides, neurokinin A (NKA) and neurokinin B(NKB), substance P (SP) was the only tachykinin identified in mammalian tissues [1,2,3]. A common precursor for SP and NKA has been identified in bovine striatum [4] and the mRNA coding for these peptides has been found in sensory neurones [5] Using radiolabelled amino acids, co-synthesis of NKA and SP in rat sensory ganglia has been demonstrated [6]. It appears that SP and NKA are co-localized in certain primary afferent neurones while NKB is localized in interneurones or ascending pathways rather than in primary afferents [7]. The role of SP, released from the peripheral terminals of sensory C-fibres in the skin, has been studied in detail and there is convincing evidence for its involvement in antidromic vasodilatation and plasma protein extravasation [8]. It is likely, however, that a part of the neurogenic vascular responses that are now attributed to SP may, in fact, be mediated by other tachykinins.