NEURONAL NICOTINIC ACETYLCHOLINE-RECEPTORS IN RAT TRIGEMINAL GANGLIA

The application of nicotine to the various epithelia served by the tri geminal nerve produces irritation and/or pain by activating neuronal n icotinic acetylcholine receptors (NnAChRS) in sensory neurons. In this study the NnAChRs were identified in rat trigeminal ganglia (TG) usin g RT-PCR and immunocytochemistry. With RT-PCR the subunits of NnAChRs in rat TG were determined, and with immunocytochemistry the localizati on of three prominent subunits (alpha 7, alpha 4 and beta 2) were loca lized in intact TG neurons. The relative abundance of the alpha and be ta subunits were: alpha 7 approximate to alpha 3 > alpha 6 > alpha 4 a pproximate to alpha 5 > alpha 9 greater than or equal to alpha 2, and beta 2 approximate to beta 3 > beta 4. This is the first report of the alpha 9 subunit in TG. Immunohistochemical studies revealed that almo st all TG neurons contained alpha 7-LI and alpha 4-LI, and that 85% ha d beta 2-LI. For these three subunits much of the label was internaliz ed. Immunocytochemical studies using antibodies raised against chick a lpha 8 subunits did not specifically label rat TG. These data reveal t hat rat TG neurons contain the entire spectrum of mammalian NnAChR sub units. (C) 1998 Elsevier Science B.V. All rights reserved.