[Substance P: immuno-allergic implications].

Substance P is a decapeptide which forms part of the group known as neuropeptides, that is, peptides released by some neurones such as the slow-conducting C fibres and the rapid-conducting A-delta fibres. These neurones belong to the category of non-adrenergic non-cholinergic nerves (NANC), which perform their action through a mechanism known as "axonic reflex". This mechanism is an antidromic stimulation which produces a secretion of neuropeptides, especially substance P. It is known that substance P, once released, is able to exert a number of actions including among others inflammatory and bronchospastic activities and a stimulation of the immunologic system. Other effects attributed to this substance are an increase in capillary permeability and oedema and the perpetuation of certain conditions such as asthma, rhinitis and chronic urticaria or hives. The production, metabolism and actions of this neuropeptide are described.