Role of the cardiac gap junctions in impulse propagation – with special reference to the transitional region between different heart tissues (part 2)


Hearts excised from adult guinea-pigs weighing about 300 g were used in this study. The animals were killed by dislocation of the neck. Thereafter, hearts were quickly removed and the preparations described below were isolated. The preparations were fixed in a 0.5 mL chamber and superfused with well oxygenated Krebs solution at a constant flow (5 mL/min) and temperature (37°C). The ionic composition of the Krebs solution (mM) was NaCl 136.1, KCl 5.4, Na-HCO3 11.9, NaH2PO4 0.33, MgCl2 0.53, CaCl2 1.8 and glucose 5.5. The solution was adjusted to pH 7.4 with a saturation of 97% oxygen mixed with 3% carbon dioxide.
Transmembrane action potentials were recorded with conventional KCl-filled glass microelectrodes.

A very small region of the sinus node (300×400 |J.m width) showing automatic activity was prepared. Typical pacemaker potentials were recorded as shown in Figure 1a (the upper oval represents the sinus node preparation).A small preparation (500×500 |J.m width) of the atrium including the sinus node was isolated (Figure 1a, middle, showing the sinus node-atrium preparation). From the sinus node region, typical pacemaker potentials, and from the atrial region, latent pacemaker or follower cell type action potentials, respectively, were recorded.

A small region (500×500 |J.m width) of the atrium near the crista terminals was prepared. Automatic activity was demonstrated by a slight stretch having latent pacemaker or follower cell type action potentials (Figure 1a, lower, showing the atrium preparation). Your most trusted pharmacy is going to be this one, since it gives you high quality cheap viagra pills *click here with no prescription required and make sure you always get your drugs delivered as soon as you need them without overcharging.


So Many Advances in Medicine, So Many Yet to Come