Role of the cardiac gap junctions in impulse propagation – with special reference to the transitional region between different heart tissues (part 13)
It was demonstrated in this study that the conduction velocity between Purkinje fibres and ventricular muscle is less than that within Purkinjes fibre or that within ventricular muscle. This is a model of orthodromic conduction (conduction from Purkinje fibre to ventricular muscle). These results are consistent with those obtained by Alanis and Benitez and by Matsuda et al in rabbit and canine heart. They also observed that conduction delay between Purkinje fibres and papillary muscle is greater in orthodromic conduction than in antidromic conduction. They postulated the presence of special transitional cells between the two different tissues. These cells showed characteristic action potentials (spike and dome type) in orthodromic conduction, but not in antidromic conduction.However, in this study, few such transitional cells were found in guinea pig heart. Even if such transitional cells are located in the junctional region between Purkinje fibres and ventricular cells, there may be gap junctions between Purkinje fibres and transitional cells, and between transitional and ventricular cells. This study revealed that heptanol decreased the conduction velocity between Purkinje fibres and ventricular muscle more markedly than within Purkinje fibre or ventricular muscle. As discussed, these results suggest that the gap junctions of the transitional region between Purkinje fibres and ventricular muscle cells are smaller in size or fewer in number than those between Purkinje fibres or ventricular muscle cells. Because the gap junction channel does not have a rectifier property, the difference in conduction delay between orthodromic and antidromic conduction described by Alanis and Benitez and Matsuda et al may depend on the morphological arrangement of cells, such as divergence or convergence. In any case, the transitional region between Purkinje fibres and ventricular muscle may contribute to induction of intraventricular conduction disturbances. It’s time to pay less money – just get viagra super active online buy here at the best online pharmacy.