Table 2.
Influence of receptor antagonists and ion channel inhibitors on chronotropism and inotropism of spontaneously beating rat atria.
| Protocols | Chronotropism (beats.min1) | Inotropism (mN) | n |
|---|---|---|---|
| R-PIA SERIES | |||
| Control | 200 ± 5 | 3.9 ± 0.7 | 40 |
| + DPCPX (100 nM) | 220 ± 4 | 3.8 ± 0.2 | 4 |
| + 4-AP (10 μM) | 210 ± 15 | 5.1 ± 0.4* | 6 |
| + Glibenclamide (10 μM) | 214 ± 26 | 4.8 ± 0.6* | 5 |
| + Tertiapin Q (300 nM) | 206 ± 14 | 3.7 ± 0.3 | 5 |
| + Apamin (30 nM) | 221 ± 11 | 4.5 ± 0.5 | 8 |
| + Nifedipine (1 μM) | 148 ± 26* | 3.7 ± 1.1 | 5 |
| + Verapamil (1 μM) | 160 ± 17* | 3.8 ± 0.6 | 5 |
| + Mibefradil (3 μM) | 169 ± 16* | 3.5 ± 0.2 | 7 |
| OXOTREMORINE SERIES | |||
| Control | 213 ± 5 | 3.5 ± 0.3 | 17 |
| + AF-DX 116 (10 μM) | 225 ± 13 | 3.2 ± 0.1 | 6 |
| + 4-AP (10 μM) | 209 ± 21 | 4.6 ± 0.4* | 5 |
| + Glibenclamide (10 μM) | 220 ± 26 | 4.1 ± 0.4* | 6 |
| + Tertiapin Q (300 nM) | 228 ± 15 | 3.6 ± 0.5 | 5 |
| + Apamin (30 nM) | 220 ± 13 | 4.0 ± 0.5 | 7 |
| + Nifedipine (1 μM) | 142 ± 26* | 3.6 ± 0.5 | 5 |
| + Verapamil (1 μM) | 165 ± 17* | 3.4 ± 0.4 | 6 |
| + Mibefradil (3 μM) | 164 ± 15* | 3.3 ± 0.2 | 6 |
| VERAPAMIL SERIES | |||
| Control | 205 ± 11 | 3.3 ± 0.3 | 14 |
| + Apamin (30 nM) | 210 ± 19 | 3.9 ± 0.4 | 7 |
| + Tertiapin Q (300 nM) | 202 ± 11 | 3.4 ± 0.2 | 5 |
| APAMIN SERIES | |||
| Control | 218 ± 6 | 3.4 ± 0.3 | 9 |
| + Verapamil (1 μM) | 157 ± 20* | 3.5 ± 0.8 | 7 |
Receptor antagonists and ion channel inhibitors were allowed to equilibrate with the preparations during 15 min before R-PIA (0.001–1 μM), oxotremorine (0.003–3 μM), verapamil (0.03–10 μM), or apamin (0.003–1 μM) application. Shown are values for atrial rate (chronotropic effect) and contractile force (inotropic effect) in the absence (Control or vehicle) and in presence of receptor antagonists and ion channel inhibitors after reaching the equilibrium, i.e., measured immediately before incubation with R-PIA, oxotremorine, verapamil, and apamin. The data are expressed as mean ± SEM from an n number of individual experiments (animals).
P < 0.05 compared with the control situation before incubation with receptor antagonists or ion channel inhibitors.