SALBUTAMOL-INDUCED AIRWAY HYPERREACTIVITY IN GUINEA-PIGS IS NOT DUE TO A LOSS OF ITS BRONCHODILATOR EFFECT

Guinea pigs were treated for 10 days with (+/-)-salbutamol (0.2 mg/kg/ day, delivered from subcutaneously implanted osmotic minipumps). Airwa y reactivity to intravenously administered histamine, methacholine and bombesin was substantially increased in salbutamol-treated guinea pig s relative to controls. In the same animals, the potency of intravenou sly administered salbutamol to reverse bombesin-induced bronchoconstri ction remained unchanged thus exactly reflecting effects in man. In co nclusion, subchronic administration of salbutamol at low doses to guin ea pigs increases airway reactivity. Since the bronchorelaxant effect of salbutamol remained unchanged, desensitisation of P-adrenoceptors o n airway smooth muscle is unlikely to account for this effect.