Meeting Abstract
Mosquitoes primarily use olfaction to seek out host animals or plants and they can remember odors associated with positive or negative experiences. However, which odors can be learned differs from species to species. Those odors associated with a preferred host may be learned more readily than less salient odors. Since anatomical neural circuitry of the olfactory system is highly conserved across mosquitoes, we hypothesized that neuromodulation by dopamine mediates species-specific differences in olfactory learning behaviors. We thus localized the dopamine precursor, tyrosine hydroxylase in the antennal lobes of four mosquito species: Aedes aegypti, Toxorhynchites amboinensis, Anopheles stephensi and Culex quinquefasciatus. Each species had a distinct pattern of dopaminergic innervation to the antennal lobes. Additionally, concentration of dopamine was markedly heterogenous across antennal lobe subunits called glomeruli. To understand the relationship between neuromodulation and olfactory learning, we used 2-photon calcium imaging in the brains of Ae. aegypti expressing gCaMP6 to record odor-evoked activity in the antennal lobes. Mosquitoes were stimulated with the odor chemicals 1-octen-3-ol, hexanoic acid, or linalool and we identified glomeruli tuned to respond to each odor. We then used quantitative immunohistochemistry to assay dopamine expression levels in the identified glomeruli. These results will be discussed in the context of mosquito performance in learning to associate each odor with an aversive stimulus in a classical conditioning paradigm. The effects of dopamine on olfactory learning in mosquitoes may have broader implications for uncovering general principals of olfaction and memory in insects and other animals.
