The guinea‐pig isolated bronchus for the in vitro study of small calibre airway reactivity

• Published in: British journal of pharmacology 1985-10, Vol.86 (2), p.367-373
• Main Authors: Advenier, Charles, Freslon, Jean‐Louis
• Format: Article
• Language: English
• Subjects: Acetylcholine - pharmacology; Airway Resistance - drug effects; Animals; Biological and medical sciences; Bronchi - drug effects; Electromyography; Female; Guinea Pigs; Histamine - pharmacology; In Vitro Techniques; Isoproterenol - pharmacology; Male; Medical sciences; Muscle Relaxants, Central - pharmacology; Pharmacology. Drug treatments; Respiratory system; Splanchnic Circulation - drug effects; Terbutaline - pharmacology; Time Factors
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1985.tb08905.x

1 Small calibre airway reactivity to different contractile and relaxant agents was tested in vitro using small segments (about 1 mm long and 0.2 mm in internal diameter) of guinea‐pig isolated intralobular bronchi. 2 EC50 values of, and maximal contractile responses to contractile agents were as follows (mean ± s.e.mean, n = 6): acetylcholine 13.6 ± 2.6 μM and 1140 ± 80 mg; histamine 5.2 ± 0.7 μM and 1094 ± 95 mg; 5‐hydroxytryptamine (5‐HT) 0.7 ± 0.1 μM and 595 ± 61 mg; prostaglandin F2α (PGF2α) 8.8 ± 1.2 μM and 1100 ± 88 mg; tetraethylammonium 2.9 ± 0.3 mM and 1055 ± 94 mg; KCl 14.6 ± 0.5 mM and 965 ± 81 mg. 3 EC50 values of, and maximal relaxant responses to β‐adrenoceptor stimulants on preparations precontracted with acetylcholine (1.4 × 10−4M) were: isoprenaline 0.40 ± 0.5 μM and 782 ± 65 mg, n = 18; salbutamol 0.19 ± 0.02 μM and 494 ± 55 mg, n = 5; terbutaline 0.87 ± 0.18 μM and 263 ± 40 mg n = 5; fenoterol 0.06 ± 0.02 μM and 722 ± 47 mg, n = 5; adrenaline 0.71 ± 0.13 μM and 653 ± 62 mg, n = 5; noradrenaline 10.8 ± 0.9 μM and 566 ± 97 mg, n = 5. 4 Differences in the maximal relaxant effects between the β‐adrenoceptor stimulants showed that the preparation utilized is a relevant model for assessment of the intrinsic activity of these drugs. 5 The high ratio (about 180) of the EC50 for noradrenaline (β1‐adrenoceptor agonist) to that for fenoterol (β2‐adrenoceptor agonist), and the lack of effect of prenalterol (β1‐adrenoceptor agonist) suggested that β2‐adrenoceptors are preferentially involved in the relaxant activity of β‐adrenoceptor stimulants in this preparation.