Sub-lethal imidacloprid exposure leads to presynaptic and postsynaptic alterations

Pesticides are commonly used in agriculture to mitigate a wide array of pests. Imidacloprid, the most frequently used neonicotinoid pesticide, has been reported to affect cholinergic signaling of off-target organisms, such as honey bees and nematodes. Taking comparative neuroscience approaches, we exposed both organisms to field-relevant sub-lethal doses of imidacloprid. In the honey bee brain, we examined microglomeruli (synaptic structures of the mushroom bodies) using synapsin immunostaining. There was a decreased density of microglomeruli following one week of imidacloprid exposure. Furthermore, to take a separate look at either side of cholinergic synapse, we used two distinct strains of transgenic nematodes labeling either presynaptic or postsynaptic cholinergic structures. Following 48 hours of exposure, we found decreased expression in both strains. These results indicate that concentrations of imidacloprid commonly occurring in the field alter the nervous systems of off-target organisms.