Mechanisms involved in DEET’s effect on the responses of bed bugs to human odorants

Human odorants are considered to be very important cues in the host-seeking process of haematophagous insects and DEET is the most wildly used chemical repellents in the insect control. Previous studies indicated that DEET exerts repellency to bed bugs although no olfactory response showed from olfactory receptor neurons (ORNs). To get insight into the mechanisms of DEET in ‘repelling’ the bed bugs, we investigated both the neuronal response of bed bugs to DEET alone and the effect of DEET in the olfactory responses of bed bugs to human odorants. When DEET was applied simultaneously with human odorants, blocking effect was observed in neuronal responses of ORNs to specific odorants. Functional study on the odorant receptors of bed bugs showed that DEET could block current responses of odorants receptors to human odorants when mixtures of DEET and human odorants were used in the stimulation. Neuron tracing experiments further confirmed activities in the antenna lobe in response to DEET and the interfering effect of DEET on the neuronal activities of antenna lobe in response to human odorants. Our study showed that DEET would function as a molecular ‘confusant’ in the host-seeking process of bed bugs to human odorants, which would benefit our understanding in the mechanisms involved in the function of DEET in the bed bug control and provide valuable information for developing new reagents in the future.