Distribution of nicotinic acetylcholine receptor subunits alpha7 and beta2 in the human brainstem and hippocampal formation

We provide the first quantification and localization of the nicotinic acetylcholine receptors (nAChRs) alpha7 and beta2 in the human adult and infant brainstem and hippocampus. After applying immunohistochemistry on formalin fixed and paraffin embedded human brain tissue, we qualitatively analyzed the staining to provide a comparison in expression amongst the brainstem nuclei and hippocampal regions, and between the infants and adults. Amongst the brainstem regions studied, the greatest protein expression for both alpha7 and beta2 subunits was in the motor nuclei of the medulla and pons. Lowest expression for both subunits was in the midbrain nuclei, except for the oculomotor nucleus. Comparison between infants and adults showed greater expression in the infant brainstem nuclei of the dorsal motor nucleus of the vagus, hypoglossal, inferior olivary nucleus, nucleus of the solitary tract, abducens, and facial nuclei, for both alpha7 and beta2 nAChRs. In the hippocampus, only the alpha7 subunit showed greater expression in infants compared to adults. We conclude that both alpha7 and beta2 containing nAChRs play an important role in many nuclei of the human infant and adult brainstem, and that the alpha7 subunit may have a more prominent role in the infant than adult hippocampus.