EVIDENCE FOR THE EXISTENCE OF ALPHA-ADRENOCEPTORS IN THE RAT LUNG

  • 1 January 1979
    • journal article
    • research article
    • Vol. 25  (2) , 215-226
Abstract
Isolated rat lung parenchymal strips responded to carbachol, 5-HT [serotonin] and phenylephrine (PE) with contractions. Bradykinin (BK), histamine, PG[prostaglandin]F2.alpha., PGE1, PGE2 and dimaprit were either inactive or produced weak relaxations. Isoproterenol, noradrenaline (NA) and epinephrine (E) relaxed lung strips. The further increase in their concentrations produced contractions of varying magnitudes. The lung strips contracted to 5-HT or carbachol, responded to isoproterenol and E and NA with relaxations. Metiamide and cimetidine (selective histamine H2-receptor antagonists) did not alter responses to histamine and carbachol. Propranolol (a .beta.-adrenoceptor blocker) antagonized or reversed relaxations to E and isoproterenol, and markedly enhanced contractions to NA, PE and E. Atropine and phentolamine or dibenzyline antagonized contractions to carbachol and sympathomimetic agents, respectively. There evidently are .alpha.- and .beta.-adrenergic receptors mediating contractions and relaxations in the peripheral airways of rat.