Chronotropic effect of ISO in isolated pacemakers of rats subjected to bilateral adrenalectomy (ADX-control), chronic stress by immobilization (IMO-7), and subjected to a combination of ADX and immobilization (ADX + IMO-7). ADX was performed 3 days before immobilization. The ratio (DR) is the quotient of the EC50 of the NI group divided by the EC50 of IMO-7 group and ADX + IMO-7 group. All other parameters are the same as in Table 1.
Group/Treatment | EC50 × 10−10 M (CI 95%) | Ratio (DR) | Initial Frequency ± S.E.M. | Maximal Frequency ± S.E.M. | Serum Corticosterone | ||
|---|---|---|---|---|---|---|---|
| μg/ml | |||||||
| ADX-control | 7 | 15.55 (10.88-19.20) | 315 ± 4 | 470 ± 15 | 0.61 ± 0.07b | ||
| IMO-7 | 8 | 2.32 (1.67-3.78)* | 6.70* | 300 ± 6 | 470 ± 10 | 3.30 ± 0.35* | |
|
ADX + IMO-7
|
8
|
11.00 (8.75-13.08)
|
1.41a
|
300 ± 10
|
463 ± 10
|
0.60 ±
0.085a,b
| |
CI, confidence interval.
↵* Significantly different from ADX-control and ADX + IMO-7 (p < 0.01).
↵ a No significant differences were found between ADX-control and ADX + IMO-7 (p > 0.05).
↵ b Significantly decreased levels of corticosterone were found between ADX-control and ADX + IMO-7 compared with NI group (p < 0.01; compare with values in Table 1).