Α4 nAChR Subunits Research Articles

Expression of α4 and β2 nicotinic acetylcholine receptor subunit mRNA and localization of α-bungarotoxin binding proteins in the rat vestibular periphery

In situ hybridization histochemistry was used to map the distribution of α2, α3, α4, and β2 nAChR subunit mRNAs throughout the peripheral vestibular system of the rat. The α4 and β2 nAChR subunit genes were co-expressed by populations of primary afferent neurons within Scarpa's ganglion, while there was no expression of the α2, α3, α4, or β2 nAChR subunit genes by type I or type II vestibular hair cells. α-bungarotoxin binding to nAChRs in the vestibular end-organs was primarily limited to the afferent chalices surrounding type I hair cells and the basal aspect of type II hair cells. These data suggest that nAChRs composed of α4 and β2 subunits are localized on afferent chalices innervating the type I vestibular hair cells and that the direct cholinergic efferent innervation of the type II vestibular hair cells utilizes nAChR composed of other subunits.

Nicotinic acetylcholine receptor subunits expressed in rat cochlea detected by the polymerase chain reaction

Poly(A) + RNA was extracted from rat cochleae using guanidinium thiocyanate and oligo(dT)-cellulose, and converted into cDNA by reverse transcriptase using an oligo(dT) primer. Oligonucleotides complementary to conserved 5′ and 3′ regions of α and β subunits of the neuronal nicotinic acetylcholine receptor subunit (nAChR) family were then used as primers to screen the cochlear cDNA via the polymerase chain reaction (PCR) procedure. PCR products of approximately 900 bp length, purified by agarose gel electrophoresis, were nick translated to produce [ 32P]-dCTP labelled probes for Southern Blot screening of nAChR cDNAs. Of the four α and three β subunits screened, only α5 and β4 nAChR cDNAs hybridized. The α5 PCR product was cloned and sequenced and proved to be identical to published sequence for α5. The detection of α5 and β4 nAChR subunit expression in cochlear tissue supports previous electrophysiological and immunocytochemical evidence for nAChR-mediated centrifugal control of hearing function.