Figure 5
Rate-dependent effects of sodium and calcium channel blockers. (A–E) Representative averaged FP (left) and FPD values (right) in control conditions (black) and after drug application (red) (A) Influence of 100 nM Verapamil on the FPD at 1 Hz (−42.8 ± 8.9%, n = 5 from 3 batches, p = 0.0087), 1.5 Hz (−43.3 ± 9.0%, n = 6 from 3 batches, p = 0.0052), 2 Hz (−39.0 ± 8.6%, n = 6 from 3 batches, p = 0.0056) and 2.5 Hz (−34.6 ± 7.1%, n = 6 from 3 batches, p = 0.0045). (B) Influence of 100 µM Lidocaine on maximum downstroke velocity (maxDV, 1.5 Hz: −69.7 ± 6.6%, p = 0.032; 2 Hz: −76.6 ± 4.4%, p = 0.014; 2.5 Hz: −75.1 ± 6.3%, p = 0.008 and 3 Hz: −68.5 ± 6.8%, p = 0.019; all n = 5 from 1 batch). (C) Influence of 100 µM Lidocaine on the FPD at 1.5 Hz (+7.5 ± 4.4%, p = 0.184), 2 Hz (+4.4 ± 5.2%, p = 0.614), 2.5 Hz (−4.5 ± 3.1%, p = 0.241) and 3 Hz (−3.8 ± 3.5%, p = 0.37; all n = 5 from 1 batch). (D) Influence of 10 µM Quinidine on maximum downstroke velocity (maxDV, 1 Hz: −80.4 ± 6.5%, n = 5 from 3 batches, p = 0.04; 1.5 Hz: −92.5 ± 2.5%, n = 5 from 2 batches, p = 0.031). (E) Effect of 10 µM Quinidine on FPD at 1 Hz (+51.8 ± 2.8%, n = 5 from 3 batches, p = 0.0004) and 1.5 Hz (+8.8 ± 5.9%, n = 5 from 2 batches, p = 0.29). In the presence of Quinidine some MEA experiments could not be paced >2 Hz indicated by a red “X” (B,C). Significances were determined using two-tailed, paired student’s t-tests. *p < 0.05, **p < 0.01, ***p < 0.001.
