Table 2.
Curve parameters for the concentration–effect curves of the inotropic effect in left atrial pectinate muscles and the chronotropic effect in right atria of young pigs
| Agonist | pEC50 | α | nH |
|---|---|---|---|
| Inotropic effect | |||
| 5-HT | 7.71±0.10 | 88.7±5.2 | 0.93±0.07 |
| Prucalopride | 7.70±0.09 | 64.3±6.7*** | 0.86±0.05 |
| Tegaserod | 6.85±0.17*** | 93.5±6.8 | 0.58±0.02 |
| R149402 | 8.97±0.08*** | 51.6±5.5*** | 0.86±0.05 |
| R199715 | 8.94±0.09*** | 32.8±6.7*** | 0.91±0.06 |
| Chronotropic effect | |||
| 5-HT (0/6) | 6.53±0.14 | 54.4±4.8 | 0.87±0.05 |
| Prucalopride (2/7) | 7.01±0.14* | 27.6±4.6*** | 1.16±0.11 |
| Tegaserod (3/6) | 6.58±0.17 | 57.6±5.7 | 0.62±0.04 |
| R149402 (1/8) | 8.53±0.15*** | 16.3±4.2*** | 1.30±0.16 |
| R199715 (1/5) | 8.70±0.17*** | 25.6±5.4*** | 1.23±0.15 |
All experiments were carried out in the presence of cocaine (6 μM) and propranolol (0.2 μM), while only in experiments with left atria IBMX (20 μM) also was added; agonists were added cumulatively. The parameters were obtained using a mixed-effects fitting procedure with the Hill equation. The values are expressed as mean±s.e.m. Numbers between brackets for the chronotropic effects represent the number of animals showing agonist-induced arrhythmic contractions.
*
P<0.05
***
P<0.001 versus corresponding values for 5-HT.