title: Capsaicin-induced avoidance behavior in the terrestrial Gastropoda Megalobulimus abbreviatus: evidence for TRPV-1 signaling and opioid modulation in response to chemical noxious stimuli.
abstract: The aim of this study was to measure the nociceptive response (avoidance latency) of the land snail Megalobulimus abbreviatus (N=8 in each group) after topical capsaicin exposure (0.1% and 0.5% in 20% ethanol) and to compare it to a well-studied stressful (50 degrees C) thermal stimulus model. We also tested if ruthenium red, and capsazepine, respectively nonselective and selective TRPV1 receptor antagonists, could modify both capsaicin- and thermal-evoked responses. Finally, animals were pretreated with morphine, naloxone or morphine plus naloxone prior to capsaicin stimuli. Latencies were measured when the animal lifted its head-foot complex 1 cm from the substrate. Data were compared using ANOVA and LSD post hoc, and the Student T Test (p<0.05). Capsaicin elicited dose-dependent withdrawal behavior. The capsaicin vehicle (20% ethanol) also evoked a less intense but significant avoidance reaction. Capsazepine and ruthenium red attenuated both capsaicin and heat withdrawal responses, when compared to vehicles. Morphine increased, and naloxone, either alone or in combination with morphine, reduced capsaicin-evoked latencies when compared to morphine or saline. These results indicate that the TRPV1 receptor plays a role in the nociceptive circuits of M. abbreviatus.
authors.affiliation: Programa de Pós-Graduação em Neurociências, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Pedro
authors.initials: P
authors.lastname: Kalil-Gaspar
authors.forename: Simone
authors.initials: S
authors.lastname: Marcuzzo
authors.forename: Paula
authors.initials: P
authors.lastname: Rigon
authors.forename: Cynthia Goulart
authors.initials: CG
authors.lastname: Molina
authors.forename: Matilde
authors.initials: M
authors.lastname: Achaval
mesh_terms: D000287:Administration, Topical; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002211:Capsaicin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects*; D011930:Reaction Time; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D012908:Snails / Q000187:drug effects* / Q000378:metabolism; D050916:TRPV Cation Channels / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D012430:Ruthenium Red; D009270:Naloxone; D009020:Morphine; C071423:capsazepine; D002211:Capsaicin