Distinct regional expression of nicotinic acetylcholine receptor genes in chick brain

Four genes (α2, α3, α4 and β2) have been reported as encoding subunits of the nicotinic acetylcholine receptor (nAChR) in chicken brain. The mRNAs transcribed from these genes have here been localised to particular regions using in situ hybridisation histochemistry. The β2 mRNA was clearly the most abundant transcript, being widely distributed throughout the chick brain. In the cerebellum, all four mRNA species were present, although they showed different cellular patterns of distribution. Only α2 mRNA and β2 mRNA were found in significant amounts in the optic tectum. In the lateral spiriform nucleus, while α2 mRNA, α4 mRNA and β2 mRNA were all very abundant, the α4 mRNA was localised to a subgroup of neurons containing α2 mRNA and β2 mRNA. This represents the first evidence that individual cells may express two different nAChR α subunit genes in vivo. The distributions of the 4 mRNA species showed few common features. This suggests that other neuronal nAChR genes remain to be identified, and that these 4 genes are not generally expressed in the same cells to constitute a single macromolecular complex. The results therefore provide evidence for nAChR heterogeneity in the central nervous system