title: Voltage-dependent gating of gap junction channels in embryonic chick ventricular cell pairs.
abstract: The dependence of macroscopic gap junctional conductance (Gj) on transjunctional voltage (Vj) was studied in paired myocytes after enzymatic dissociation of 7-day-old embryonic chick ventricles. The membrane voltage of both cells was independently controlled by separate patch-clamp circuits in the whole cell configuration. Two distinctive unitary junctional conductances were identified in recordings from seven different cell pairs. The larger channel had a mean conductance of 166 +/- 37 pS (n = 6 pairs), whereas a second channel averaged 58 +/- 10 pS (n = 3). Instantaneous Gj remained linear over a Vj range of -100 to +100 mV, whereas the steady-state Gj declined when voltages exceeded +/- 30 mV. Both decay and recovery phases of Gj follow exponential time courses, with the recovery time constant being four times slower than inactivation, requiring 1.1 s at 80 mV. The normalized steady-state Gj-Vj curve could be defined by a two-state Boltzmann distribution, assuming an effective gating charge of 1.72, a half-inactivation voltage of 45 mV, and a residual voltage-insensitive Gj of 27% of maximum. Single-channel recordings revealed closure of 160-pS channels on a Vj step to 80 mV, and the ensemble average of five such records produced an exponentially decaying junctional current with a time constant of 184 ms. The single-channel current-voltage relationship remains linear with a slope of 145 pS over the entire Vj range. The results support the hypothesis that a population of 160-pS gap junction channels is gated by transjunctional potentials.
authors.affiliation: Department of Pharmacology, State University of New York, Syracuse 13210.
authors.forename: R D
authors.initials: RD
authors.lastname: Veenstra
mesh_terms: D000818:Animals; D002450:Cell Communication; D002478:Cells, Cultured; D002642:Chick Embryo; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D006321:Heart / Q000502:physiology*; D007365:Intercellular Junctions / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D013997:Time Factors; D016276:Ventricular Function