Decrease in DEET repellency caused by nitric oxide in Rhodnius prolixus.
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 microg/cm2). 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 microg/cm2), suggesting an adaptation phenomenon. The pre-treatment of the insects with 15 microg /insect of SNAC or 2 microg/insect of db-cGMP produced a reduction of the repellency. An increase in locomotor activity was observed in insects exposed to 350 or 700 microg/cm2 DEET. Although exposure to 70 microg/cm2 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 microg/cm2 of DEET showed no differences in locomotor activity compared to controls.
Sfara
Valeria
V
Centro de Investigaciones de Plagas e Insecticidas (CIPEIN-CITEFA/CONICET), (B1603ALO) Villa Martelli, Prov. de Buenos Aires, Argentina. vsfara@citefa.gov.ar
Zerba
Eduardo N
EN
Alzogaray
Raúl A
RA
D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D003671:DEET / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007302:Insect Repellents / Q000494:pharmacology*; D009569:Nitric Oxide / Q000494:pharmacology*; D012903:Smell; D014225:Triatominae / Q000187:drug effects*
D007302:Insect Repellents; D003671:DEET; D009569:Nitric Oxide; D006152:Cyclic GMP