Guanine nucleotides modulate steady-state inactivation of voltage-gated sodium channels in frog olfactory receptor neurons.
The voltage for half-inactivation (V1/2) of Na+ currents in frog olfactory receptor neurons (ORNs) under whole-cell voltage clamp showed a shift to more negative potentials with time. Inclusion of guanosine triphosphate (GTP) or its nonhydrolyzable analogue, guanosine-5'-O-3-thiotriphosphate (GTP-gamma-S), which activates G proteins, in the recording pipette, not only gave a more positive V1/2, but also reduced and delayed the negative shift observed in the absence of nucleotides. Guanosine-5'-O-2-thiodiphosphate (GDP-beta-S), a nonhydrolyzable analogue that prevents the binding of GTP to G proteins, did not affect the V1/2 significantly by itself but blocked the positive shift induced by GTP. Since the steady-state activation was not affected, our results indicate that a G protein or a G-protein-dependent process may be important in regulating the steady-state inactivation of Na+ channels in ORNs of the frog.
Pun
R Y
RY
Department of Molecular and Cellular Physiology, University of Cincinnati, Ohio 45267-0576.
Kleene
S J
SJ
Gesteland
R C
RC
D000818:Animals; D019204:GTP-Binding Proteins / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011894:Rana pipiens; D015398:Signal Transduction / Q000502:physiology; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013873:Thionucleotides / Q000494:pharmacology
D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins