Figure 5.
(A) Average Ij – Vj curves for heterotypic Cx43/Cx40 gap junctions obtained with symmetrical internal patch pipette solutions (black symbols and lines) or in the presence of 2 mM spermine (gray symbols and lines) added to the Cx40-side of the heterotypic gap junction. The lines indicate the steady-state curve obtained with a continuous 200 ms/mV Vj ramp and the symbols indicate the steady-state Ij value obtained at the end of a 20 sec Vj pulse to the indicated Vj value. (B) The same as in panel A except the 2 mM spermine was added to the Cx43-side of the heteroypic Cx43/Cx40 gap junction. (C) Actual current traces from 2 different experiments illustrating the effect of 2 mM spermine added to the Cx43-side of a Cx43/Cx40 heterotypic gap junction during the −/+/−50 mV Vj pulse sequence of the cationic block Vj clamp protocol. (D) The Vj-dependent spermine inhibition curves for homotypic Cx40 (•) or Cx43 (▪) gap junctions and the heterotypic Cx43/Cx40 gap junction with spermine added to either the Cx40-positive or Cx43-positive side of the gap junction. The fraction of Ij block for the heterotypic gap junction was calculated relative to the heterotypic gap junction currents in the absence of spermine for each side of the junction.