title: Beta-adrenoceptor-mediated facilitation of endogenous noradrenaline release from rat isolated trachea.
abstract: Overflow of endogenous noradrenaline from rat isolated trachea was evoked by electrical field stimulation (3 Hz, 540 pulses) in the presence of yohimbine, desipramine and tyrosine. Isoprenaline 100 nmol/l increased the evoked overflow of noradrenaline by about 65%. This effect was antagonized by propranolol (100 nmol/l) and the beta 2-selective adrenoceptor antagonist ICI 118,551 (100 nmol/l), but not by the beta 1-selective adrenoceptor antagonist CGP 20712 A (100 nmol/l). The beta 2-selective adrenoceptor agonist formoterol (1-100 nmol/l) also facilitated the evoked overflow of noradrenaline, but maximally by only about 25% at 10 nmol/l, i.e. formoterol behaved as a partial agonist at these facilitatory beta-adrenoceptor. This assumption is also supported by the observation that formoterol (10 nmol/l) acted as antagonist against isoprenaline (100 nmol/l). Mechanical removal of the mucosa resulted in a 30% decrease in tissue noradrenaline and a 55% reduction of the evoked overflow of noradrenaline. In mucosa-denuded preparations isoprenaline failed to facilitate noradrenaline overflow. In the presence of indomethacin (3 mumol/l) the evoked overflow of noradrenaline from mucosa containing preparations was increased by about 50%, but isoprenaline still further facilitated the evoked noradrenaline overflow by about 40%. In conclusion, the overflow of noradrenaline in the rat trachea is facilitated via beta 2-adrenoceptors, an effect which requires an intact airway mucosa.
authors.affiliation: Department of Pharmacology, University of Frankfurt, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Brunn
authors.forename: I
authors.initials: I
authors.lastname: Wessler
authors.forename: G P
authors.initials: GP
authors.lastname: Anderson
authors.forename: J
authors.initials: J
authors.lastname: Maclagan
authors.forename: K
authors.initials: K
authors.lastname: Racké
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D015398:Signal Transduction; D014132:Trachea / Q000294:innervation / Q000378:metabolism*
chemical_list: D018663:Adrenergic Agents; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D009638:Norepinephrine; D007213:Indomethacin