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  • Title: Parasympathetic and adrenergic contractile responses in canine trachea and bronchus.
    Author: Leff AR, Munoz NM, Hendrix SG.
    Journal: J Appl Physiol Respir Environ Exerc Physiol; 1983 Jul; 55(1 Pt 1):113-20. PubMed ID: 6885560.
    Abstract:
    We compared the sympathetic and parasympathetic contractile responses of tracheal and third-order bronchial smooth muscle simultaneously in 26 dogs in situ. Stimulus-response curves were generated by bilateral stimulation of the cervical vagus nerves in five dogs to determine the parameters (20 V, 15 Hz, 2-ms duration) causing maximal parasympathetic contraction in trachea and bronchus. In six adrenal-intact (ADi) and five adrenalectomized (ADx) dogs, sympathetically mediated alpha-adrenergic contraction was studied after muscarinic and beta-adrenergic blockade by administering intravenous (iv) 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP). In ADi dogs, the maximal alpha-adrenergic contractile response to iv DMPP was 67.3 +/- 14.8% of the maximal parasympathetic response in trachea and 112 +/- 21% of the maximal parasympathetic response in bronchus (P less than 0.03). In ADx dogs, the maximal alpha-adrenergic-to-parasympathetic stimulation ratios were 17.6 +/- 1.3% in trachea and 41.4 +/- 2.5% in bronchus (P less than 0.001). Comparable relationships were also obtained in pharmacological studies of alpha-adrenergic and cholinergic responses in trachea and bronchus. We conclude that there is substantial heterogeneity in the physiological and pharmacological cholinergic and alpha-adrenergic contractile properties in trachea and bronchus. Relative to cholinergic contraction, both circulating catecholamines and sympathetic innervation cause substantially greater alpha-adrenergic contraction in bronchus than for tracheal smooth muscle.
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