Single-cell quantitative expression of nicotinic acetylcholine receptor mRNA in rat hippocampal interneurons

Hippocampal interneurons are a very diverse population of cells. Using single-cell quantitative PCR to analyze rat CA1 hippocampal interneurons, we quantified neuronal nicotinic acetylcholine receptor (nAChR) mRNA subunit expression and detailed possible nAChR subtype combinations for the alpha 2, alpha 3, alpha 4, alpha 5, alpha 7, beta 2, beta 3, and beta 4 subunits. We also compared the expression detected in the stratum oriens and the stratum radiatum hippocampal layers. We show that the majority of interneurons in the CA1 of the rat hippocampus contain detectable levels of nAChR subunit mRNA. Our results highlight the complexity of the CA1 nAChR population. Interestingly, the alpha 3 nAChR subunit is one of the highest expressed subunit mRNAs in this population, while the alpha 4 is one of the least likely subunits to be detected in CA1 interneurons. The beta 2 nAChR subunit is the highest expressed beta subunit mRNA in these cells. In addition, Pearson's correlation coefficient values are calculated to identify significant differences between the nAChR subunit combinations expressed in the CA1 stratum oriens and the stratum radiatum. Statistical analysis also indicates that there are likely over 100 different nAChR subunit mRNA combinations expressed in rat CA1 interneurons. These results provide a valid avenue for identifying nAChR subtype targets that may be effective hippocampus-specific pharmacological targets.