Immunocytochemical localization of the alpha3, alpha4, alpha5, alpha7, beta2, beta3 and beta4 nicotinic acetylcholine receptor subunits in the locus coeruleus of the rat.

The presence of nicotinic acetylcholine receptors (nAChRs) within the locus coeruleus (LC) has been examined using a wide range of techniques. However, the expression pattern of individual nicotinic receptor subunits has not been described. Using immunocytochemistry, we demonstrate the distribution of the alpha3, alpha4, alpha5, alpha7, beta2, beta3 and beta4 nAChR subunits within the LC. Most nAChR subunits were expressed on neuronal perikarya within the LC nucleus. The alpha3, alpha4, alpha7 and beta3 immunoreactive neurons were evenly distributed in the dorsal and ventral LC whereas the alpha5, beta2 and beta4 nAChR subunits were preferentially confined to the upper dorsal section. In addition to neuronal perikarya, alpha4, alpha5 and beta2 immunoreactive fibers were observed. With the exception of the alpha3 subunit, punctate labeling was observed within and immediately surrounding the LC. These data are consistent with the presence of multiple nAChRs within the LC and extend these findings to show the distribution pattern of each nAChR subunit throughout the LC nucleus.