title: Ca2+ channel currents in dorsal root ganglion neurons of P/Q-type voltage-gated Ca2+ channel mutant mouse, rolling mouse Nagoya.
abstract: The role of the P/Q-type voltage-gated Ca(2+) channels (VGCCs) in release of neurotransmitters involved in nociception is not fully understood. Rolling mouse Nagoya (tg(rol)), a P/Q-type channel mutant mouse, expresses P/Q-type VGCC whose activation curve has a higher half activation potential and a smaller slope factor than the wild type channel. We previously reported that tg(rol) mice showed hypoalgesic responses to noxious stimuli. In this study, we examined the VGCC current in dorsal root ganglion (DRG) neurons by the whole-cell patch-clamp method. Both ω-agatoxin IVA (0.1 μM) and ω-conotoxin GVIA (1 μM) inhibited the VGCC current by about 40-50% in both the homozygous tg(rol) (tg(rol)/tg(rol)) and wild type (+/+) mice. The voltage-activation relationships of the total VGCC current and the ω-agatoxin IVA-sensitive component in the tg(rol)/tg(rol) mice shifted positively compared to the +/+ mice, whereas that sensitive to the ω-conotoxin GVIA was not different between the two genotypes. The time constant of activation of the VGCC current at -20 mV was longer in the tg(rol)/tg(rol) mice than in the +/+ mice. These changes in the properties of the VGCC in the tg(rol)/tg(rol) mouse may reduce the amount of the released neurotransmitters and account for the hypoalgesic responses.
authors.affiliation: Department of Veterinary Physiology, Faculty of Agriculture, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8553, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Fukumoto
authors.forename: Naoki
authors.initials: N
authors.lastname: Kitamura
authors.forename: Kimie
authors.initials: K
authors.lastname: Niimi
authors.forename: Eiki
authors.initials: E
authors.lastname: Takahashi
authors.forename: Chitoshi
authors.initials: C
authors.lastname: Itakura
authors.forename: Izumi
authors.initials: I
authors.lastname: Shibuya
mesh_terms: D000818:Animals; D020865:Calcium Channels, P-Type / Q000235:genetics*; D020907:Calcium Channels, Q-Type / Q000235:genetics*; D020013:Calcium Signaling / Q000235:genetics*; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008818:Mice, Neurologic Mutants; D008822:Mice, Transgenic; D009619:Nociceptors / Q000166:cytology / Q000502:physiology*; D061251:Primary Cell Culture
chemical_list: D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type