title: Characterization of Na+ and Ca2+ channels in zebrafish dorsal root ganglion neurons.
abstract: BACKGROUND
  Dorsal root ganglia (DRG) somata from rodents have provided an excellent model system to study ion channel properties and modulation using electrophysiological investigation. As in other vertebrates, zebrafish (Danio rerio) DRG are organized segmentally and possess peripheral axons that bifurcate into each body segment. However, the electrical properties of zebrafish DRG sensory neurons, as compared with their mammalian counterparts, are relatively unexplored because a preparation suitable for electrophysiological studies has not been available.
  
  
  RESULTS
  We show enzymatically dissociated DRG neurons from juvenile zebrafish expressing Isl2b-promoter driven EGFP were easily identified with fluorescence microscopy and amenable to conventional whole-cell patch-clamp studies. Two kinetically distinct TTX-sensitive Na(+) currents (rapidly- and slowly-inactivating) were discovered. Rapidly-inactivating I(Na) were preferentially expressed in relatively large neurons, while slowly-inactivating I(Na) was more prevalent in smaller DRG neurons. RT-PCR analysis suggests zscn1aa/ab, zscn8aa/ab, zscn4ab and zscn5Laa are possible candidates for these I(Na) components. Voltage-gated Ca(2+) currents (I(Ca)) were primarily (87%) comprised of a high-voltage activated component arising from ω-conotoxin GVIA-sensitive Ca(V)2.2 (N-type) Ca(2+) channels. A few DRG neurons (8%) displayed a miniscule low-voltage-activated component. I(Ca) in zebrafish DRG neurons were modulated by neurotransmitters via either voltage-dependent or -independent G-protein signaling pathway with large cell-to-cell response variability.
  
  
  CONCLUSIONS
  Our present results indicate that, as in higher vertebrates, zebrafish DRG neurons are heterogeneous being composed of functionally distinct subpopulations that may correlate with different sensory modalities. These findings provide the first comparison of zebrafish and rodent DRG neuron electrical properties and thus provide a basis for future studies.
authors.affiliation: Section on Transmitter Signaling, Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Won
authors.forename: Fumihito
authors.initials: F
authors.lastname: Ono
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Ikeda
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D005727:Ganglia, Spinal / Q000166:cytology* / Q000378:metabolism; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D015640:Ion Channel Gating; D007700:Kinetics; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D018377:Neurotransmitter Agents; D020033:Protein Isoforms; D012333:RNA, Messenger; D018080:Receptors, GABA-B; D015222:Sodium Channels; D029961:Zebrafish Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D019204:GTP-Binding Proteins