Biophysical properties of voltage-gated Na+ channels in frog parathyroid cells and their modulation by cannabinoids
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- Yukio Okada
- Integrative Sensory Physiology, Graduate School of Biomedical Sciences,Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
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- Kotapola G. Imendra
- Department of Physiology, Faculty of Medicine, University of Rhuna, Galle,Sri Lanka
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- Toshihiro Miyazaki
- Oral Cytology and Cell Biology, Graduate School of Biomedical Sciences,Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
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- Hitoshi Hotokezaka
- Orthodontics and Biomedical Engineering, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
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- Rie Fujiyama
- Integrative Sensory Physiology, Graduate School of Biomedical Sciences,Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
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- Jorge L. Zeredo
- Integrative Sensory Physiology, Graduate School of Biomedical Sciences,Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
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- Takenori Miyamoto
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Bunkyo-ku, Tokyo 112-8681, Japan
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- Kazuo Toda
- Integrative Sensory Physiology, Graduate School of Biomedical Sciences,Nagasaki University, Nagasaki, Nagasaki 852-8588, Japan
抄録
<jats:title>SUMMARY</jats:title> <jats:p>The membrane properties of isolated frog parathyroid cells were studied using perforated and conventional whole-cell patch-clamp techniques. Frog parathyroid cells displayed transient inward currents in response to depolarizing pulses from a holding potential of –84 mV. We analyzed the biophysical properties of the inward currents. The inward currents disappeared by the replacement of external Na+ with NMDG+ and were reversibly inhibited by 3 μmol l–1 TTX, indicating that the currents occur through the TTX-sensitive voltage-gated Na+channels. Current density elicited by a voltage step from –84 mV to–24 mV was –80 pA pF–1 in perforated mode and–55 pA pF–1 in conventional mode. Current density was decreased to –12 pA pF–1 by internal GTPγS (0.5 mmol l–1), but not affected by internal GDPβS (1 mmol l-1). The voltage of half-maximum (V1/2)activation was –46 mV in both perforated and conventional modes. V1/2 of inactivation was –80 mV in perforated mode and –86 mV in conventional mode. Internal GTPγS (0.5 mmol l–1) shifted the V1/2 for activation to–36 mV and for inactivation to –98 mV. A putative endocannabinoid,2-arachidonoylglycerol ether (2-AG ether, 50 μmol l–1) and a cannabinomimetic aminoalkylindole, WIN 55,212-2 (10 μmol l–1) also greatly reduced the Na+ current and shifted the V1/2 for activation and inactivation. The results suggest that the Na+ currents in frog parathyroid cells can be modulated by cannabinoids via a G protein-dependent mechanism.</jats:p>
収録刊行物
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- Journal of Experimental Biology
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Journal of Experimental Biology 208 (24), 4747-4756, 2005-12-15
The Company of Biologists