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. 2013 Mar 13;33(11):4741–4753. doi: 10.1523/JNEUROSCI.2825-12.2013

Figure 3.

Figure 3.

[Mg2+]i-dependent modulation of gj and Vj-gating of GJs formed by other Cxs expressed in CNS does not affect single-channel conductance. A, C, E, Changes of Ij in response to repeated 50-s-long Vj ramps from 0 to −100 mV and intermediate small-amplitude steps (−15 mV) using [Mg2+]p = 5 mm in Novikoff (A), HeLa Cx45 (C), and HeLa Cx47-EGFP (E) cell pairs. B, D, F, First (purple) and last (cyan) gj–Vj relations (normalized to initial gj value at Vj = 0) obtained from experiments shown in A, C, and E, respectively. Last gj–Vj relation normalized to gj value at Vj = 0 (gray) is also shown for comparison. G, Concentration–response relation of gj (normalized to initial gj value) as a function of [Mg2+]p for Cx47; EC50 ≈ 2.8 mm. Averaged data are shown in colored circles; roman numerals correspond to different pipette solutions shown in Table 1. H, Averaged gj–Vj dependence (normalized to gj at Vj = 0) obtained at different [Mg2+]p for Cx47; roman numerals correspond to different [Mg2+] shown in G and Table 1. Experimental gj–Vj plots shown in black were fitted using the S16SM; calculated values of gating parameters are shown in Table 2, and the best-fitting gj–Vj plots are shown in colors that correspond to colors of circles in G. I, J, Open probabilities of fast and slow gates in α and β aHCs (PoF,α, PoS,α and PoF,β, PoS,β, respectively) depending on Vj were calculated using parameters obtained in H for [Mg2+]p = 0.01 (I) and 10 mm (J). K, Ij record of Cx43-CFP GJs obtained at Vj = −80 mV. L, Histogram from data in K shows a series of peaks separated by ∼96.5 ± 8 pS. M, Single-channel conductance for Cx47-EGFP obtained in response to a Vj step of −52 mV. The histogram shows peaks for the closed state, substate (γs = 11.2 ± 2.3 pS), and open state (γo = 49 ± 5.6 pS). The arrowhead indicates a slow transition from the closed state to open state, and the arrow indicates a fast transition from the open state to the substate. N, Ij trace from a HeLa Cx47-EGFP cell pair in response to 1.5-s-long Vj ramps from 90 to −90 mV using [Mg2+]p = 5 mm after 32, 37, and 42 min of recording.