The actions of the neonicotinoid imidacloprid on cholinergic neurons of Drosophila melanogaster.
Jepson JE., Brown LA., Sattelle DB.
The neonicotinoid insecticide imidacloprid is an agonist on insect nicotinic acetylcholine receptors (nAChRs). We utilised fura-2-based calcium imaging to investigate the actions of imidacloprid on cultured GFP-tagged cholinergic neurons from the third instar larvae of the genetic model organism Drosophila melanogaster. We demonstrate dose-dependent increases in intracellular calcium ([Ca2+]i) in cholinergic neurons upon application of imidacloprid (10 nM-100 muM) that are blocked by nAChR antagonists mecamylamine (10 microM) and alpha-bungarotoxin (alpha-BTX, 1 microM). When compared to other (untagged) neurons, cholinergic neurons respond to lower concentrations of imidacloprid (10-100 nM) and exhibit larger amplitude responses to higher (1-100 microM) concentrations of imidacloprid. Although imidacloprid acts via nAChRs, increases in [Ca2+]i also involve voltage-gated calcium channels (VGCCs) in both groups of neurons. Thus, we demonstrate that cholinergic neurons express nAChRs that are highly sensitive to imidacloprid, and demonstrate a role for VGCCs in amplifying imidacloprid-induced increases in [Ca2+]i.