Role of the cardiac gap junctions in impulse propagation – with special reference to the transitional region between different heart tissues (part 8)
Effects of heptanol on conduction velocity: The conduction velocity within the Purkinje fibre (P-P), within ventricular muscle (V-V), and between the Purkinje fibre and ventricular muscle (orthodromic conduction) (P-V) was 0.95±0.01, 0.63±0.02 and 0.42±0.02 m/s (mean ± SEM), respectively. Heptanol (0.1 to 1.0 mM) had a deteriorative effect on conduction velocity in P-P, V-V and P-V, with no change in resting membrane potential and Vmax of the action potential.Changes over time in the conduction velocity of P-P, V-V and P-V are shown in Figure 7a. Ten minutes after application of 1.0 mM heptanol, the conduction velocity of P-P, V-V and P-V was decreased to 90%, 75% and 65%, respectively, of control value. The dose-dependent effect of heptanol on the conduction velocity of P-V, V-V and P-V are shown in Figure 7b. At a relatively lower concentration of heptanol, the conduction velocity of P-V deteriorated markedly. The effect of the agent 20 mins later at a concentration of 0.5 mM was almost the same as that 10 mins later at a concentration of 1.0 mM. Impairment of conduction velocity was most marked in P-V, less marked in V-V and least marked in P-P.
Figure 7 a Effect of 1.0 mM heptanol on conduction velocity within the Purkinje fibre (P-P), within ventricular muscle (V-V) and between the Purkinje fibre and ventricular muscle (P-V). b Effect of 0.1 or 0.4 mM heptanol on conduction velocity in P-P, V-V and P-V. Each point and bar (a), and each column and bar (b) are mean ± SEM. *P<0.01 versus P-P. Conduction velocity is given in relative values (where control = 1.0)
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