title: The zebrafish ortholog of TRPV1 is required for heat-induced locomotion.
abstract: The ability to detect hot temperatures is critical to maintaining body temperature and avoiding injury in diverse animals from insects to mammals. Zebrafish embryos, when given a choice, actively avoid hot temperatures and display an increase in locomotion similar to that seen when they are exposed to noxious compounds such as mustard oil. Phylogenetic analysis suggests that the single zebrafish ortholog of TRPV1/2 may have arisen from an evolutionary precursor of the mammalian TRPV1 and TRPV2. As opposed to TRPV2, mammalian TRPV1 is essential for environmentally relevant heat sensation. In the present study, we provide evidence that the zebrafish TRPV1 ion channel is also required for the sensation of heat. Contrary to development in mammals, zebrafish TRPV1(+) neurons arise during the first wave of somatosensory neuron development, suggesting a vital importance of thermal sensation in early larval survival. In vitro analysis showed that zebrafish TRPV1 acts as a molecular sensor of environmental heat (≥25°C) that is distinctly lower than the sensitivity of the mammalian form (≥42°C) but consistent with thresholds measured in behavioral assays. Using in vivo calcium imaging with the genetically encoded calcium sensor GCaMP3, we show that TRPV1-expressing trigeminal neurons are activated by heat at behaviorally relevant temperatures. Using knock-down studies, we also show that TRPV1 is required for normal heat-induced locomotion. Our results demonstrate for the first time an ancient role for TRPV1 in the direct sensation of environmental heat and show that heat sensation is adapted to reflect species-dependent requirements in response to environmental stimuli.
authors.affiliation: Department of Biological Structure, Neurobiology and Behavior Graduate Program, and Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Philia
authors.initials: P
authors.lastname: Gau
authors.forename: Jason
authors.initials: J
authors.lastname: Poon
authors.forename: Carmen
authors.initials: C
authors.lastname: Ufret-Vincenty
authors.forename: Corey D
authors.initials: CD
authors.lastname: Snelson
authors.forename: Sharona E
authors.initials: SE
authors.lastname: Gordon
authors.forename: David W
authors.initials: DW
authors.lastname: Raible
authors.forename: Ajay
authors.initials: A
authors.lastname: Dhaka
mesh_terms: D000143:Acids / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D002273:Carcinogens / Q000494:pharmacology; D057809:HEK293 Cells; D006358:Hot Temperature; D006801:Humans; D053403:Lateral Line System / Q000166:cytology / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D008969:Molecular Sequence Data; D011984:Sensory Receptor Cells / Q000502:physiology*; D018689:Sensory System Agents / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000819:agonists / Q000235:genetics / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014276:Trigeminal Nerve / Q000166:cytology / Q000502:physiology; D015027:Zebrafish / Q000235:genetics / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D000143:Acids; D002273:Carcinogens; D018689:Sensory System Agents; D050916:TRPV Cation Channels; C581231:TRPV1 protein, zebrafish; C494484:TRPV1 receptor; D029961:Zebrafish Proteins; D013755:Tetradecanoylphorbol Acetate; D002211:Capsaicin