Substance P and neurotensin

This chapter describes two neuropeptides, substance P (SP) and neurotensin (NT). These two neuropeptides contain sequences analogous to tuftsin. Moreover, these peptides and their partial sequences containing the tuftsin-related domains displace labeled tuftsin from phagocytes and enhance their phagocytic capability. Both peptides exhibit a broad spectrum of pharmacological effects in the central nervous system as well as at the periphery. SP is widespread in both central and peripheral nervous systems. At the periphery, SP is recognized for its hypotensive, vasodilatory, and smooth muscle-contracting properties. In the central nervous system, SP is suggested to play a role in sensory nerve transmission. NT is distributed in various parts of the brain, gastrointestinal tissues, plasma, and in synovial tissue and fluid. SP is released from sensory nerves following injury, axon reflex, and antidromic stimulation, and thus is thought to be involved in neurogenic inflammation. Both SP and NT have properties and are located or released at sites that can enable them to act as mediators at various stages of inflammatory reactions.