Electrical properties of gap junction channels in guinea-pig ventricular cell pairs revealed by exposure to heptanol

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Abstract
Cell pairs were isolated from adult guinea pig ventricles to study the electrical properties of gap junction channels. The experiments involved a double voltage-clamp approach and whole-cell, tight-seal recording. Heptanol decreased the intracellular current, In, in a dose-dependent fashion. Before complete uncoupling, In showed fluctuations suggesting the operation of gated channels. In the presence of 3 mM heptanol, In showed quantal steps arising from spontaneous opening and closing of single channels. The IV-relationship of the channels was linear (range: ±95 mV). Analysis of current records revealed the following singlechannel conductances, γn: Mean value = 37 pS; median value = 33 pS. γn was insensitive to the non-junctional membrane potential (range: −90 to +10 mV). 3 mM ATP4− in the pipette solution had no effects on γn, 6 mM ATP4− produced a small decrease, and 6 mM ATP+0.1 mM cAMP− an increase in γn. Channel transitions from closed to open state were variable (range of apparent time constants: 2.5–32 ms; mean: 11 ms).