Hone_2012_FASEB.J_26_917

The alpha6-containing nicotinic acetylcholine receptors (nAChRs) have recently been implicated in diseases of the central nervous system (CNS), including Parkinson's disease and substance abuse. In contrast, little is known about the role of alpha6* nAChRs in the peripheral nervous system (where the asterisk denotes the possible presence of additional subunits). Dorsal root ganglia (DRG) neurons are known to express nAChRs with a pharmacology consistent with an alpha7, alpha3beta4*, and alpha4beta2* composition. Here we present evidence that DRG neurons also express alpha6* nAChRs. We used RT-PCR to show the presence of alpha6 subunit transcripts and patch-clamp electrophysiology together with subtype-selective alpha-conotoxins to pharmacologically characterize the nAChRs in rat DRG neurons. alpha-Conotoxin BuIA (500 nM) blocked acetylcholine-gated currents (I(ACh)) by 90.3 +/- 3.0%; the recovery from blockade was very slow, indicating a predominance of alpha(x)beta4* nAChRs. Perfusion with either 300 nM BuIA[T5A;P6O] or 200 nM MII[E11A], alpha-conotoxins that target the alpha6beta4* subtype, blocked I(ACh) by 49.3 +/- 5 and 46.7 +/- 8%, respectively. In these neurons, I(ACh) was relatively insensitive to 200 nM ArIB[V11L;V16D] (9.4+/-2.0% blockade) or 500 nM PnIA (23.0+/-4% blockade), alpha-conotoxins that target alpha7 and alpha3beta2*/alpha6beta2* nAChRs, respectively. We conclude that alpha6beta4* nAChRs are among the subtypes expressed by DRG, and to our knowledge, this is the first demonstration of alpha6beta4* in neurons outside the CNS.