Apisalpha2, Apisalpha7-1 and Apisalpha7-2: three new neuronal nicotinic acetylcholine receptor alpha-subunits in the honeybee brain.

Acetylcholine is the principal excitatory neurotransmitter in the central nervous system of insects. Nicotinic acetylcholine receptors, which belong to the ligand-gated ion channel family, constitute important targets for insecticides. In the honeybee Apis mellifera, pharmacological evidence supports the existence of several nicotinic acetylcholine receptors. In this paper, we report the identification of three new genes that encode nicotinic acetylcholine receptor alpha-subunits in the honeybee. Phylogenetic comparisons with other ligand-gated ion channel subunit sequences support their classification as Apisalpha2, Apisalpha7-1 and Apisalpha7-2 subunits. Based on in situ hybridization experiments, we determined their expression patterns in the different brain regions of pupae and adult honeybees. Our results show that these nicotinic acetylcholine receptor subunits are differently expressed among the brain regions and that they appear at different stages of honeybee development.