Monoterpenoid binding at the house fly (Musca domestica) nicotinic acetylcholine receptor

Essential oils are hydrophobic liquids obtained from plant materials and contain volatile aroma compounds, in particular various monoterpenoids.  Botanical compounds, including essential oils and terpenoids, have gained interest as alternatives to synthetic insecticides because of their safety and decreased non-target toxicity.  Several aromatic and aliphatic monoterpenoids have been shown to be toxic to insects.  Their precise mechanism of toxic action is not known, and several mechanisms have been suggested.  The nicotinic acetylcholine receptor (nAChR) is an important insecticide target.  The nAChR is the target of natural nicotinoids (nicotine, epibatidine), as well as spinosad and synthetic insecticides (neonicotinoids).  Recently, we have demonstrated in house fly nAChR that a naturally occurring aromatic monoterpenoid, carvacrol, inhibits the binding of ¹⁴C-nicotine in a concentration-dependent manner.  Further characterization of the binding of ¹⁴C-nicotine in the presence of nicotinoids (nicotine and epibatidine) and neonicotinoids (imidacloprid, dinotefuran, and thiamethoxam) will also be presented.