Decrease in deet repellency caused by nitric oxid in Rhodnius prolixus

SFARA, VALERIA; ZERBA, EDUARDO N; ALZOGARAY, RAÚL A

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY

Wiley

Lugar: New York; Año: 2008 vol. 67 p. 1 - 8

0739-4462

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, nitrosoacetyl-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/square cm. 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/square cm, suggesting an adaptation phenomenon. The pre-treatment of the insects with 15 µg/insect of SNAC or 2 µg/insect of dbcGMP produced a reduction of the repellency. An increase in locomotor activity was observed in insects exposed to 350 or 700 µg/square cm of DEET. Although exposure to 70 µg/square cm of 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/square cm of DEET showed no differences in locomotor activity compared to controls.