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Non‐adrenergic, non‐cholinergic neural activation stabilizes smooth‐muscle tone independently of eicosanoid factors in guinea‐pig isolated airways
Author(s) -
Lindén A.,
Ullman A.,
Löfdahl CG.,
Skoogh BE.
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb12459.x
Subject(s) - guanethidine , medicine , cholinergic , guinea pig , stimulation , endocrinology , contraction (grammar) , muscle contraction , atropine , adrenergic , trachealis muscle , chemistry , biology , respiratory system , receptor , respiratory epithelium
1 We examined the effect of variations in resting smooth‐muscle tone induced by eicosanoid inhibitors on the direction and magnitude of the non‐adrenergic, non‐cholinergic (NANC) nervous response in guinea‐pig isolated airways. 2 NANC responses (in the presence of 1 μ m atropine, 10 μ m guanethidine) to electrical field stimulation (1200 mA; 0.5 ms; 240 s; 3 Hz) were studied in guinea‐pig isolated airway preparations ( n = 4–7) taken from the proximal trachea, the distal trachea and the main bronchus. Tissues were treated with either the cyclo‐oxygenase‐blocker, indomethacin (10 μ m ), or the leukotriene receptor antagonist, FPL 55712 (11.5 μ m ), to modulate the resting tone. 3 Depending on the level of resting tone prior to electrical field stimulation, NANC activation induced either a contraction or a relaxation converging towards a similar level of tone, a ‘tonus equilibrium’. This tonus equilibrium displayed an increasing level towards the periphery (3 ± 3 (s.e.mean) % for the proximal trachea, 28 ± 3% for the distal trachea and 54 ± 4% for the main bronchus, in % of maximum active tension). After NANC activation, the tonus returned to a level similar to the resting tone. 4 We conclude that changes in resting smooth‐muscle tone not only affect the magnitude but also the direction of the NANC response. It is suggested that the NANC nervous system is a stabilizing factor in the regulation of airway smooth‐muscle tone, independent of eicosanoid factors. An increasing contractile component and a decreasing relaxant component of the NANC system towards the peripheral airways is indicated.