Figure 3.

Typical examples of the decreases in junctional conductance promoted by testosterone propionate (TP) and estradiol propionate (EP) in ventricular myocytes of newborn rat. A (top) Both cells of the pair were clamped at a common holding potential (−70 mV) and a 10 mV depolarization was applied to one of them every 30 s, whereas the second cell was maintained at the holding potential. (Bottom) Because of the transjunctional driving force, a current flows through cell-to-cell channels, and its amplitude was seen to decrease gradually when the cell pair was exposed to TP (superimposed currents recorded the 5 first min after TP introduction). B Corresponding time courses of the decreases in junctional conductances (G/G0)when the cells, at first bathed in Tyrode’s solution (), were exposed to a stream of a steroid-containing solution (25 μM) applied close to the cell pair (filled symbols). The junctional conductance, presented in units of its original value, was found to decline progressively in the presence of both TP (▪) and EP (▴) to complete interruption of the cell-to-cell communication