科研之友
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摘要
This study compares the potency and efficacy of different relaxant drugs including anticholinergic, beta-adrenergic and methylxanthine agents on acetylcholine-contracted feline bronchi, and investigates the influence of the initial muscarinic-induced tone on bronchodilator response. Feline bronchi were removed from euthanased client-owned cats and were contracted with acetylcholine to cause either 40% or 80% of the acetylcholine maximal contraction. The efficacy and potency of bronchodilating drugs were obtained from cumulative dose-response curves with efficacy (E-max) as the maximal relaxant response and potency (-log EC50) as the logarithm of the concentration of drug inducing 50% of maximal relaxation. %26lt;br%26gt;Under low contractile tone (40%), all bronchodilators relaxed feline bronchi in a concentration-dependent manner with the following rank order of potency: formoterol %26gt; ipratropium bromide %26gt; fenoterol %26gt; isoprenaline %26gt; salbutamol %26gt;= salmeterol %26gt; theophylline. E-max values ranged from 80% to 100% depending on the tested drug. Constriction of feline bronchi with high-dose acetylcholine (80%) caused a rightward and downward shift of the beta(2)-mimetic dose-response curves. Significant decreases in -log EC50 and E-max values were reported for salbutamol, formoterol and salmeterol. This study provides evidence that existing classes of bronchodilators produce effective relaxation of acetylcholine-contracted feline bronchi and that airway responsiveness to beta(2)-stimulants is dependent on the magnitude of the initial muscarinic-induced tone. The clinical relevance of these in vitro findings has yet to be explored in clinical trials.
- 出版日期2012-7
