title: Thermosensation and the TRPV channel in Rhodnius prolixus.
abstract: The thermal sense of triatomine bugs, vectors of Chagas disease, is unique among insects. Not only do these bugs exhibit the highest sensitivity to heat known in any animal up to date, but they can also perceive the infrared radiation emitted by the body of their warm-blooded hosts. The sensory basis of this capacity has just started to be unravelled. To shed additional light on our understanding of thermosensation, we initiated an analysis of the genetic basis of the thermal sense in Rhodnius prolixus. We tested the hypothesis that a TRPV (transient receptor potential vanilloid) channel receptor is involved in the evaluation of heat in this species. Two different approaches were adopted. Initially, we analysed the expression of a TRPV candidate for this function, i.e., RproIav, in different tissues. Subsequently, we tested the effects of capsaicin and capsazepine, two molecules known to interact with mammal TRPV1, using three different behavioural protocols for evaluating thermal responses: (1) proboscis extension response (PER), (2) thermopreference in a temperature gradient and (3) spatial learning in an operant conditioning context. Bioinformatic analyses confirmed that the characteristic features typical of the TRPV channel subfamily are found in the RproIav protein sequence. Molecular analysis showed that RproIav is expressed in R. prolixus, not only in the antennae, but also in other body structures bearing sensory organs. Behavioural experiments consistently revealed that capsaicin treated insects are less responsive to heat stimuli and prefer lower temperatures than non-treated insects, and that they fail to orient in space. Conversely, capsazepine induces the opposite behaviours. The latter data suggest that triatomine thermoreception is based on the activation of a TRP channel, with a similar mechanism to that described for mammal TRPV1. The expression of RproIav in diverse sensory structures suggests that this receptor channel is potentially involved in bug thermoreception. This constitutes solid evidence that thermosensation could be based on the activation of TRP receptors that are expressed in different tissues in R. prolixus. Whether RproIav channel is a potential target for the compounds tested and whether it mediates the observed effects on behaviour still deserves to be confirmed by further research.
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261 CNRS, Université François Rabelais de Tours, France; Departamento de Ecología, Genética y Evolución, Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: Paula F
authors.initials: PF
authors.lastname: Zermoglio
authors.affiliation: Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte, Brazil.
authors.forename: José M
authors.initials: JM
authors.lastname: Latorre-Estivalis
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261 CNRS, Université François Rabelais de Tours, France; Departamento de Ecología, Genética y Evolución, Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
authors.forename: José E
authors.initials: JE
authors.lastname: Crespo
authors.affiliation: Centro de Pesquisas René Rachou, FIOCRUZ, Belo Horizonte, Brazil.
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Lorenzo
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR 7261 CNRS, Université François Rabelais de Tours, France. Electronic address: claudio.lazzari@univ-tours.fr.
authors.forename: Claudio R
authors.initials: CR
authors.lastname: Lazzari
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology; D014355:Chagas Disease; D003216:Conditioning, Operant; D005247:Feeding Behavior / Q000187:drug effects; D015870:Gene Expression; D006358:Hot Temperature; D007303:Insect Vectors; D008969:Molecular Sequence Data; D012239:Rhodnius / Q000187:drug effects / Q000502:physiology*; D065853:Spatial Learning / Q000187:drug effects; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D013697:Thermosensing
chemical_list: D050916:TRPV Cation Channels; C071423:capsazepine; D002211:Capsaicin
keywords: Capsaicin; Capsazepine; Chagas disease vectors; TRPV; Thermal sense