Table 5.
Cough-related variables before and after intravenous administration of clonidine (n = 6) and tizanidine (n = 4)
| CN | TT (sec) | TI (sec) | TE (sec) | PPA (RU) | PAA (RU) | |
|---|---|---|---|---|---|---|
| Mechanical stimulation | ||||||
| Control | 3.6 ± 0.21 | 0.58 ± 0.02 | 0.39 ± 0.02 | 0.19 ± 0.01 | 0.58 ± 0.03 | 0.63 ± 0.03 |
| 40–60 μg/kg clonidine | 1.5 ± 0.22** | 0.84 ± 0.04* | 0.53 ± 0.04* | 0.31 ± 0.04* | 0.52 ± 0.02 | 0.43 ± 0.04* |
| 80–120 μg/kg clonidine | − | − | − | − | − | − |
| Citric acid inhalation | ||||||
| Control | 4.7 ± 0.42 | 0.51 ± 0.01 | 0.35 ± 0.01 | 0.16 ± 0.01 | 0.57 ± 0.02 | 0.58 ± 0.01 |
| 40–60 μg/kg clonidine | 1.7 ± 0.21** | 0.72 ± 0.05* | 0.46 ± 0.03* | 0.26 ± 0.02* | 0.53 ± 0.03 | 0.36 ± 0.02** |
| 80–120 μg/kg clonidine | − | − | − | − | − | − |
| Mechanical stimulation | ||||||
| Control | 3.5 ± 0.29 | 0.57 ± 0.02 | 0.38 ± 0.03 | 0.19 ± 0.01 | 0.61 ± 0.03 | 0.66 ± 0.04 |
| 150 μg/kg tizanidine | 1.5 ± 0.29* | 0.82 ± 0.02* | 0.49 ± 0.03* | 0.33 ± 0.03* | 0.51 ± 0.03 | 0.42 ± 0.06* |
| 300 μg/kg tizanidine | − | − | − | − | − | − |
| Citric acid inhalation | ||||||
| Control | 4.2 ± 0.42 | 0.51 ± 0.01 | 0.35 ± 0.01 | 0.16 ± 0.01 | 0.57 ± 0.02 | 0.58 ± 0.01 |
| 150 μg/kg tizanidine | 1.3 ± 0.22** | 0.70 ± 0.03* | 0.44 ± 0.02* | 0.27 ± 0.02* | 0.55 ± 0.03 | 0.40 ± 0.02** |
| 300 μg/kg tizanidine | − | − | − | − | − | − |
Values are means ± SEM; n, number of animals; CN, cough number; TT, cycle duration; TI, inspiratory time; TE, expiratory time; PPA, peak phrenic activity in relative units (RU); PAA, peak abdominal activity in relative units (RU). Negative marks indicate the absence of cough responses. *P < 0.05; **P < 0.005 compared with control cough.