The Nature and Electrophysiological Properties of the Afferent Neurons Involved in Neurogenic Inflammation in the Skin

Abstract

Abstract In all species studied so far, neurogenic inflammation is generated by subclasses of C-fiber nociceptor, although the particular subclass varies between species. In pig and human skin, the key neurons are mechanically insensitive (heat nociceptors and/or silent nociceptors) and polymodal nociceptors are not involved. In the rat and rabbit, a proportion of polymodal nociceptors produce antidromic vasodilatation (ADV) and, in the rat, also plasma extravasation. It is likely that the neurogenic inflammation-producing neurons are from the population that contains the peptides substance P and/or calcitonin gene-related peptide. In the pig, the heat nociceptors that are the only group causing ADV have relatively long duration axonal action potentials. In other species, nociceptive dorsal root ganglion (DRG) neurons all tend to have long duration action potentials, involving significant tetrodotoxin-resistant sodium currents and possibly calcium currents. There is no information on the specific electrophysiological properties of the subpopulation of nociceptive DRG neurons involved in neurogenic inflammation.