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. 2004 Jul 8;559(Pt 2):479–496. doi: 10.1113/jphysiol.2004.068213

Figure 3. Action potentials from cell clusters are sensitive to TTX.

Figure 3

A and B, APs from a representative cluster in control bath solution. Note that the AP rhythm was regular. B, expanded view of A to illustrate AP morphology. Dotted line indicates 0 mV. C and D, 3 μm TTX slowed spontaneous rate of AP initiation. D, expanded view of C; in comparison to control (A) the major effect of 3 mm TTX was to slow the spontaneous diastolic depolarization. E, washout of TTX shows the effects are reversible. F, summary data from 6 recordings shows that 3 μm TTX: (a) slowed the maximum upstroke velocity (Vmax), (b) slowed the diastolic depolarization rate (DDR), and (c) prolonged the diastolic interval. All the effects were statistically significant (P < 0.01). Fd, APD is plotted as a function of the time required for 10, 20, 50, 75 and 90% of repolarization. Control APD (▪) tended to be shorter than APD in the presence of TTX (○), but the differences were not significant. n = 6 for all panels. G, APs from a representative cluster in control, 10 μm TTX and following washout. 10 μm TTX induced quiescence and was accompanied by a slow steady depolarization to ∼−40 mV. Note break in time scale due to relative prolonged washout duration.