Alpha-9 nicotinic acetylcholine receptor immunoreactivity in the rodent vestibular labyrinth

• Published in: Journal of comparative neurology (1911) Vol. 492; no. 3; pp. 323 - 333
• Main Authors: Luebke, Anne E., Maroni, Paul D., Guth, Scott M., Lysakowski, Anna
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 21.11.2005
• Subjects: Animals; Chinchilla; crista ampullaris; Ear, Inner - cytology; Ear, Inner - metabolism; efferent; Guinea Pigs; hair cells; Immunohistochemistry; macular organ; Neurons - cytology; Neurons - metabolism; otolith; Rats; Receptors, Nicotinic - metabolism; Rodentia; vestibular ganglion
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.20739

Vestibular tissues (cristae ampullares, macular otolithic organs, and Scarpa's ganglia) in chinchilla, rat, and guinea pig were examined for immunoreactivity to the α9 nicotinic acetylcholine receptor (nAChR) subunit. The α9 antibody was generated against a conserved peptide present in the intracellular loop of the predicted protein sequence of the guinea pig α9 nAChR subunit. In the vestibular periphery, staining was observed in calyces around type I hair cells, at the synaptic pole of type II hair cells, and in varying levels in Scarpa's ganglion cells. Ganglion cells were also triply labeled to detect α9, calretinin, and peripherin. Calretinin labels calyx‐only afferents. Peripherin labels bouton‐only afferents. Dimorphic afferents, which have both calyx and bouton endings, are not labeled by calretinin or peripherin. In these experiments, α9 was expressed in both calyx and dimorphic afferents. A subpopulation of small ganglion cells did not contain the α9 nAChR but did stain for peripherin. We surmise that these are bouton‐only afferents. Bouton (regularly discharging) afferents also show efferent responses, although they are qualitatively different from those in irregularly discharging (calyx and dimorphic) afferents, much slower and longer lasting. Thus, regular afferents are probably more affected via a muscarinic cholinergic or a peptidergic mechanism, with a much smaller superimposed fast nicotinic‐type response. This latter response could be due to one of the other nicotinic receptors that have been described in studies from other laboratories. J. Comp. Neurol. 492:323–333, 2005. © 2005 Wiley‐Liss, Inc.