The skin as an organ for the study of the pharmacology of neuropeptides.

There is good evidence that some vascular effects of inflammation in the skin are neurogenic and involve axon reflexes in the terminal arborizations of C-fibres containing substance P, neurokinin A and calcitonin gene-related peptide (CGRP). Substance P produces dose-related wheal and flare reactions in human skin. Neurokinin A induces wheal but little or no flare and is less potent than substance P. CGRP induces both wheal and flare but is also less potent than substance P. In addition, CGRP induces a slow-onset, intense vasodilatation in human skin which persists for several hours and is associated with leucocyte infiltration: a response which is not seen with substance P. Substance P also releases histamine from mast cells in the skin and the presence or absence of a role for histamine and mast cells in neurogenic inflammation in skin is discussed.