title: Physiological and behavioral evidence of a capsaicin-sensitive TRPV-like channel in the medicinal leech.
abstract: Transient receptor potential vanilloid (TRPV) channels are found throughout the animal kingdom, where they play an important role in sensory transduction. In this study, we combined physiological studies with in vivo behavioral experiments to examine the presence of a putative TRPV-like receptor in the medicinal leech, building upon earlier studies in this lophotrochozoan invertebrate. The leech polymodal nociceptive neuron was activated by both peripheral and central application of the TRPV1-activator capsaicin in a concentration-dependent manner, with 100 μmol l(-1) being the lowest effective concentration. Responses to capsaicin were inhibited by the selective TRPV1 antagonist SB366791. The polymodal nociceptive neuron also responded to noxious thermal stimuli (>40°C), and this response was also blocked by SB366791. Capsaicin sensitivity was selective to the polymodal nociceptor with no direct response being elicited in the mechanical nociceptive neuron or in the non-nociceptive touch- or pressure-sensitive neurons. Capsaicin also elicited nocifensive behavioral responses (withdrawals and locomotion) in a concentration-dependent manner, and these behavioral responses were significantly attenuated with SB366791. These results suggest the presence of a capsaicin-sensitive TRPV-like channel in the medicinal leech central nervous system and are relevant to the evolution of nociceptive signaling.
authors.affiliation: Center for Brain and Behavior Research, Division of Basic Biomedical Sciences, Sanford, School of Medicine, University of South Dakota, Vermillion, SD 57069, USA.
authors.forename: Torrie
authors.initials: T
authors.lastname: Summers
authors.affiliation: Center for Brain and Behavior Research, Division of Basic Biomedical Sciences, Sanford, School of Medicine, University of South Dakota, Vermillion, SD 57069, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Holec
authors.affiliation: Center for Brain and Behavior Research, Division of Basic Biomedical Sciences, Sanford, School of Medicine, University of South Dakota, Vermillion, SD 57069, USA bburrell@usd.edu.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Burrell
mesh_terms: D000813:Anilides / Q000494:pharmacology; D000818:Animals; D002211:Capsaicin / Q000378:metabolism / Q000494:pharmacology*; D002934:Cinnamates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D047709:Hirudo medicinalis / Q000187:drug effects* / Q000502:physiology; D006358:Hot Temperature; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D018689:Sensory System Agents / Q000378:metabolism / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000813:Anilides; D002934:Cinnamates; C477659:N-(3-methoxyphenyl)-4-chlorocinnamanilide; D018689:Sensory System Agents; D050916:TRPV Cation Channels; D002211:Capsaicin
keywords: Invertebrate; Leech; Nociception; TRPV