DEET Scrambled the Olfactory Response of Bed Bugs to Human Odorants

Human odorants are considered to be very important cues in the host-seeking process of haematophagous insects, including the bed bug, Cimex lectularious. DEET is the most wildly used chemical repellents in the insect control. Although DEET exerts repellency to bed bugs in the behavioral studies, no olfactory receptor neuron (ORNs) responses have been detected. To get insight into the mechanism of DEET in ‘repelling’ the bed bugs, we, for the first time, investigated the effect of DEET on olfactory responses of bed bugs to human odorants. With 104 human odorants applied in the test, only 43 of them elicited excitatory response on either type of olfactory sensilla. Different types of sensilla displayed very distinctive responses to human odorants. When DEET was applied simultaneously with human odorants, an odorant-specific scrambling effect in the odor coding of ORNs was observed. Our functional study on the odorant receptors of bed bugs demonstrated that DEET could block current responses of odorants receptors to human odorants when mixtures of DEET and human odorants were used in the stimulation, suggesting that DEET functions as a molecular ‘confusant’ in the host-seeking process of bed bugs to human odorants – the mechanism of DEET in ‘repelling’ bed bugs.