DISSOCIATION OF DORSAL-ROOT GANGLION NEURONS INTO AFFERENT AND EFFERENT-LIKE NEURONS

Although the textbook function of dorsal root ganglion neurons is to s ignal information to the brain, a group of C-fibre and some AG-fibre a fferents have the capacity to release peptide transmitters from their peripheral terminations and thereby to regulate vascular and other tis sue activities. Depending on the species under study, vasoactive dorsa l root ganglion neurons in the skin belong to heat nociceptors or a su bclass of polymodal nociceptors, and it has been a matter of long-stan ding discussion how the local effector role of dorsal root ganglion ne urons is related to their afferent function. The observation that loca l vascular regulation may take place independently of nociception has commonly been explained by a number of transductional differences betw een peripheral peptide release and afferent nerve activity. However, t he view that it is only one population of dorsal root ganglion neurons that can work in either mode is increasingly challenged, and after co nsideration of the available information we hypothesize that some dors al root ganglion neurons are specialized in controlling peripheral eff ector mechanisms but have no role in sensation. These local effector n eurons represent a novel class of autonomic neurons that lack a pregan glionic input, but operate in an efferent-like mode after stimulation by internal or external stimuli. (C) 1998 IBRO. Published by Elsevier Science Ltd.