NEUROGENIC VASODILATATION AND PLASMA LEAKAGE IN THE SKIN

1. Primary afferent nerve fibers control cutaneous blood flow and vasc ular permeability by releasing vasoactive peptides. These vascular rea ctions and the additional recruitment of leukocytes are commonly embod ied in the term neurogenic inflammation. 2. Calcitonin gene-related pe ptide (CGRP) acting via CGRP(1) receptors is the principal transmitter of neurogenic dilatation of arterioles whereas substance P (SP) and n eurokinin A (NKA) acting via NK1 receptors mediate the increase in ven ular permeability. 3. Neurogenic vasodilatation and plasma protein lea kage play a role in inflammation because many inflammatory and immune mediators including interleukin-1 beta, nitric oxide, prostanoids, pro tons, bradykinin, histamine, and 5-hydroxytryptamine can stimulate pep tidergic afferent nerve fibers or enhance their excitability, 4. Neuro genic inflammatory reactions can be suppressed by alpha(2)-adrenocepto r agonists, histamine acting via H-3 receptors, 5-hydroxytryptamine ac ting via 5-HT1B receptors, opioid peptides, and somato statin through prejunctional inhibition of peptide release from vasoactive afferent n erve fibers. CGRP, SP, and NKA receptor antagonists are powerful pharm acological tools to inhibit neurogenic inflammation at the postjunctio nal level. 5. Imbalance between the facilitatory and inhibitory influe nces on afferent nerve activity has a bearing on chronic inflammatory disease. Impaired nerve function represents a deficit in skin homeosta sis while neuronal overactivity is a factor in allergic and hyperreac tive disorders of the skin. (C) 1998 Elsevier Science Inc.