抄録
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 using perforated and conventional whole-cell patch-clamp techniques. The inward currents disappeared by the replacement of external Na+ with NMDG+ and were reversibly inhibited by 3 μM TTX, indicating that the currents occur through the TTX-sensitive voltage-gated Na+ channels. Current density elicited by a voltage step from -84 to -24 mV was -80 pA/pF in perforated mode and -55 pA/pF in conventional mode. Internal GTPγS (0.5 mM) decreased the density to -12 pA/pF, but internal GDPβS (1 mM) did not affect the density. The voltage (V1/2) of half-maximum activation was -46 mV in both of perforated and conventional modes. The voltage (V1/2) of half-maximum inactivation was -80 mV in perforated mode and -86 mV in conventional mode, respectively. Internal GTPγS (0.5 mM) shifted the V1/2 for activation to -36 mV and the V1/2 for inactivation to -98 mV. The results suggest that the Na+ currents in frog parathyroid cells can be modulated by a G protein-dependent mechanism. [Jpn J Physiol 55 Suppl:S69 (2005)]
