NONADRENERGIC, NONCHOLINERGIC FUNCTION IN THE HUMAN AIRWAY

Alterations in non-adrenergic, non-cholinergic (NANC) function may con tribute to nocturnal asthma. We have attempted to clarify the importan ce of the NANC system in the circadian variation in airway calibre in mild asthmatics and nocturnal asthmatics. NANC function in the human a irway was studied at 0400 and 1600 hours in 12 nocturnal asthmatics an d 12 mild asthmatics by measuring oscillatory resistance (Ros) followi ng capsaicin inhalation. Measurements were made after combined beta- a nd atropinic blockade in the mild asthmatics but after atropinic block ade alone in the nocturnal asthmatics, in whom beta-blockade is contra indicated. To determine whether beta-blockade influences NANC bronchod ilatation, we also studied 12 normal subjects with and without beta-bl ockade at 1600 hours only. The mild asthmatics showed differing (P=0.0 07) resistance changes 1-3 min after capsaicin at 1600 hours (fall in Ros+1%, CI -2% to 3%) from that at 0400 hours (-4%, CI -8% to -1%) but the nocturnal asthmatics showed no significant difference in response to capsaicin at the two times (fall in Res: 1600 hours -9%, CI -15% t o -3%; 0400 hours -3%, -7% to 1%). The normal subjects showed greater (P=0.0001) bronchodilatation 1-3 min after capsaicin following atropin e plus propranolol (-7%, -11% to -3%) than after atropine alone (-2%, -6% to 2%), supporting interaction between the beta-sympathetic and NA NC systems in the human airway, NANC bronchodilatation being inhibited by beta-sympathetic activity. Our observations confirm circadian vari ation in NANC function in mild asthmatics and suggest interaction betw een the beta-adrenergic and the NANC bronchodilating system in the nor mal human airway.