title: Strongly alkaline pH avoidance mediated by ASH sensory neurons in C. elegans.
abstract: High pH is a noxious stimulus to animals, and their ability to avoid dangerously alkaline pH is critical for survival. However, the means by which they sense high pH has not been determined. The nematode Caenorhabditis elegans (C. elegans) avoids environmental pH above 10.5. In contrast, C. elegans mutants with structurally, developmentally, and/or functionally abnormal sensory cilia fail to avoid high pH, suggesting that sensory neurons in the cilia participate in sensing. Genetic rescue of the mutants indicates that ASH polymodal sensory neurons play a vital role in the process. Consistently, specific laser ablation of ASH neurons made animals insensitive to high pH. Furthermore, avoidance assays of other mutants also indicated that transient receptor potential vanilloid type (TRPV) ion channels encoded by osm-9 and ocr-2 are involved in sensing. Indeed, genetic rescue of osm-9 mutants by specifically expressing OSM-9 in ASH showed that TRPV channels play an essential role in sensing of high pH. Ca(2+) imaging in vivo also revealed that ASH neurons were activated by high pH stimulation, but ASH of osm-9 or ocr-2 mutants were not. These results demonstrate that in C. elegans, high pH is sensed by ASH nociceptors through opening of OSM-9/OCR-2 TRPV channels.
authors.affiliation: Information Processing Biology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami, Okinawa 904-0495, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Sassa
authors.forename: Takashi
authors.initials: T
authors.lastname: Murayama
authors.forename: Ichi N
authors.initials: IN
authors.lastname: Maruyama
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001362:Avoidance Learning; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002633:Chemotaxis; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011984:Sensory Receptor Cells / Q000502:physiology*; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D009419:Nerve Tissue Proteins; C464590:OCR-2 protein, C elegans; C108820:OSM-9 protein, C elegans; D050916:TRPV Cation Channels; D002118:Calcium
keywords: Alkalinity; Avoidance behavior; Caenorhabditis elegans; Chemotaxis; Nociceptor; TRPV channel