Development of an odor blend to attract triatomines: responses of central olfactory neurons

IBARRA BOUZADA, LUCIA; MAY CONCHA, I; BRATOVICH C; CECERE C; ROJAS LEÓN J; GUERENSTEIN, P.G.

Encuentro; X Encontro Brasileiro de Ecologia Química; 2017

Chagas diseasestill remains as an important vector-borneneglected tropical disease. In the absence of an effective treatment forchronic human infection or vaccines, the prevention of vector-bornetransmission of Chagas disease in endemic areas relies on suppressing houseinfestations by triatomine bugs. Triatomainfestans is the main triatomine vector species in the southern conecountries of South America. We aim at developing an efficient host-based odor blend attractant tobe used as a lure in a trap to monitor triatomines. In insects, odorants are detectedby olfactory receptor cells (ORCs) mainly on the antenna. Insect ORCs projectto the antennal lobe (AL) in the brain. The AL is the firstinformation-processing center of the olfactory system. It is known that odormixtures are more attractive than single odorants. In order to understand howinformation about potentially attractive odor mixtures is processed in thetriatomine brain, and to speed up the development of such attractive blends itis necessary to study the responses of AL neurons to single odorants andmixtures of them. Although some information about the odor tuning andphysiology of the triatomine ORCs is available, nothing is known about how odorinformation is processed in the triatomine AL. Using a multichannel recordingtechnique we recorded the activity of neurons in the AL of T. infestans nymphs upon stimulation with both natural blends andsynthetic odorants. Responses were obtained to mouse odor, human breath and chicken odor. In addition, responses to anumber of synthetic odorants or their mixtures were also obtained. Thosesynthetic odorants included a-pinene, valericacid, 1-octen-3-ol, nonanal, isobutyric acid, isobutilamine, and ammonia.Response types included cessation of spikes (hereafter inhibition), excitation,inhibition-excitation and excitation-inhibition. Dose-dependent responses tosynthetic odorants were found. However, surprisingly, in several cases lowerconcentrations of odorants evoked higher responses than higher concentrations.Moreover, the response to a single odorant could be opposite (i.e., excitationvs. inhibition) depending on the odorant concentration. Funding: ANPCyT (PICT 2015 N3260) andCONICET (PIP 2015-2017), Argentina