Abstract
N,N‐diethyl‐3‐methylbenzamide (DEET) is widely used as an insect repellent; however, little is known about its mode of action. On the other hand, nitric oxide (NO) participates in the olfaction transduction pathway of insects. In this work, nitroso‐acetyl‐cysteine (SNAC), a nitric oxide donor, or dibutyril‐cyclic‐GMP (db‐cGMP), the cyclic nucleotide analog, were applied on fifth instar nymphs of Rhodnius prolixus before exposing them to DEET, to obtain information about the possible role of NO/cGMP system in the olfaction process. In the first place, we exposed the nymphs to several DEET concentrations (70, 700, 1,750, and 3,500 μg/cm^2^). All these concentrations produced a repellent effect. A decrease in repellency during the course of the experiment was observed when the nymphs were exposed to high concentrations of DEET (700 and 1,750 μg/cm^2^), suggesting an adaptation phenomenon. The pre‐treatment of the insects with 15 μg /insect of SNAC or 2 μg/insect of db‐cGMP produced a reduction of the repellency. An increase in locomotor activity was observed in insects exposed to 350 or 700 μg/cm^2^ DEET. Although exposure to 70 μg/cm^2^ DEET produced a high repellency response, it did not modify the insects' locomotor activity. Insects treated with two doses of SNAC before being exposed to 350 μg/cm^2^ of DEET showed no differences in locomotor activity compared to controls. Arch. Insect Biochem. Physiol. 67:1–8, 2008. © 2007 Wiley‐Liss, Inc.