Capsazepine affects thermal preferences of the American cockroach (Blattodea: Blattidae)

Abstract

ISSN (online): 1802-8829http://www.eje.cz capsaicin induces preferences for lower temperatures in Rhodnius prolixus, while capsazepine treatment cause the opposite behaviour.The aim of our study was to assess the effect of capsazepine (TRPV1 antagonist) on the thermal preference of the American cockroach, Periplaneta americana. American cockroach has TRP receptors. Wicher et al. (2005) screened the Periplaneta cDNA library for members of the TRPC family and found a homolog of the Drosophila TRPɣ channel. It is proposed that it is involved in forming the channel that conducts the Ca 2+ background current in DUM neurons. Recently, French et al. (2015) demonstrated that the TRPL channel has a major role in Periplaneta phototransduction.Based on our preliminary results we hypothesized that capsazepine infl uences thermoregulatory processes in insects. To confi rm this hypothesis, we examined thermal preferences of cockroaches treated with fi ve different capsazepine concentrations and released in a thermal gradient system. To establish whether capsazepine may act as a capsaicin antagonist in insects, we assessed the insect thermoregulatory response to capsaicin following pretreatment with capsazepine. We assumed that capsazepine blocks the insects' hypothermic response to capsaicin, as in mammals (Dogan et al., 2004). MATERIALS AND METHODS InsectsAmerican cockroaches Periplaneta americana L. were reared in plastic containers at ~ 26°C under a natural photoperiod. They were fed with oat fl akes and apples and received drinking water at regular intervals. Only adult individuals were selected for the experiments. Experiments were performed separately on males Abstract. Capsazepine is a competitive antagonist of capsaicin, a TRPV1 agonist responsible for the spicy taste of pepper. TRPV1 agonists and antagonists are known to affect mammalian body temperature, but their action on thermoregulation in insects is poorly known. In this study we evaluated the effect of capsazepine on the thermal preference of the American cockroach, Periplaneta americana using a thermal gradient. Our results revealed that capsazepine in submicromolar concentrations induces a preference for higher ambient temperatures when compared to the control insects. To assess whether capsazepine may act also as an antagonist of capsaicin in insects, we determined this insects' thermal behaviour when capsazepine was applied before capsaicin. The hypothermic response to capsaicin was clearly blocked by pre-treatment with capsazepine only in female American cockroaches. Our results indicate the involvement of structures functionally similar to TRPV1 in insect thermosensation.

Altered heat nociception in cockroach Periplaneta americana L. exposed to capsaicin

“…On the other hand, capsaicin is often used as an insect repellent [ 46 ]. Experiments conducted on mealworm larvae and on the American cockroach using a thermal gradient showed that insects respond to capsaicin and capsazepine by modifying their thermal preferences [ 36 ; 47 ]. Mealworms intoxicated with capsaicin or capsazepine responded similarly to mammals (in mealworms, capsaicin induced preference for lower temperatures, while capsazepine for higher temperatures).…”

“…Experiments were performed in a thermal gradient using an identical method as described previously [ 36 ]. Briefly, after five days of drug administration, each individual cockroach (n = 12 for each drug) was placed in the thermal gradient trough and its thermal preferences were observed for 24 hours.…”

Effect of Capsaicin and Other Thermo-TRP Agonists on Thermoregulatory Processes in the American Cockroach

“…In mammals, this alkaloid has been shown to induce hypothermia that occurs both at physiological (skin vasodilation, suppression of thermogenesis and salivation) and behavioral (cold-seeking behavior) response levels [1,2,3,4]. Some reports have shown the effect of capsaicin on thermoregulatory processes in invertebrates such as an induced preference for lower temperatures in Periplaneta americana [5] or Leptinotarsa decemlineata [6]. Moreover, exposure to this alkaloid has been reported to change the responsiveness to noxious heat in the American cockroach [7] and in land snail Megalobulimus abbreviatus [8].…”

“…Kohno et al [18] demonstrated that the injection of menthol, which suppresses the activity of HsTRPA, induces bees preference for warmer regions. Zermoglio et al [22], Olszewska and Tęgowska [23] and Maliszewska and Tęgowska [5] studied the effect of capsaicin and capsazepine on insects’ thermal preferences and their results suggest the existence of structures sensitive to these substances. Detailed analysis of the effect of selected ligands on thermoregulatory processes is presented in Table 2.…”

“…We studied the effect of various ligands that have been shown to activate (allyl isothiocyanate) or inhibit (camphor) warm receptors, as well as activate (camphor) or inhibit (menthol and thymol) cold receptors in insects. In our previous studies [5,7], we demonstrated changes in thermal preferences in cockroaches exposed to capsaicin and capsazepine; thus, the present study was aimed at determining only the body temperature changes after exposure to these ligands. This let us observe whether tested TRP ligands change physiological thermoregulation.…”