Itch is described as an unpleasant or irritating skin sensation that elicits the desire or reflex to scratch. MrgprA3, one of members of the Mrgprs family, is specifically expressed in a subpopulation of dorsal root ganglion (DRG) in the peripheral nervous system (PNS). These MrgprA3-expressing DRG neurons have been identified as itch-specific neurons. They can be activated by the compound, chloroquine, which is used as a drug to treat malaria. In the present study, we labeled these itch-specific neurons using the method of molecular genetic markers, and then studied their electrophysiological properties. We also recorded the cutaneous MrgprA3^– neurons retrogradely labeled by Dil dye (MrgprA3^–-Dil). We first found that MrgprA3⁺ neurons have a lower excitability than MrgprA3^– neurons (MrgprA3^–-non-Dil and MrgprA3^–-Dil). The number of action potential (AP) was reduced more obviously in MrgprA3⁺ neurons than that of in MrgprA3^– neurons. In most cases, MrgprA3⁺ neurons only generated single AP; however, in MrgprA3^– neurons, the same stimulation could induce multiple AP firing due to the greater voltage-gated potassium (Kv) current existence in MrgprA3⁺ than in MrgprA3^– neurons. Thus, Kv current plays an important role in the regulation of excitability in itch-specific neurons.

Copyright © 2016. Published by Elsevier B.V.