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Regulation of bronchomotor tone in conscious calves
Author(s) -
GUSTIN P.,
DHEM A. R.,
LEKEUX P.,
LOMBA F.,
LANDSER F. J.,
WOESTIJNE K. P. VAN DE
Publication year - 1989
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.1989.tb00642.x
Subject(s) - propranolol , yohimbine , isoprenaline , medicine , endocrinology , respiratory system , chemistry , anesthesia , stimulation , receptor , antagonist
The purpose of this study was to investigate the effects of some a and β sympathomimetic and sympatholytic drugs on respiratory impedance in healthy conscious calves. Ten Friesian calves were investigated in this study. The forced oscillation technique was used to measure the resistance ( R rs ) and the reactance ( X rs ) of the respiratory system at frequencies ranging from 4 to 26 Hz. Isoprenaline (1 μg/kg i.v.), propranolol (3 μg/kg i.v.), noradrenaline (2 μg/kg i.v.), xylazine (20 μg/kg i.v.) and yohimbine (0.25 mg/kg i.v.) were administered. Isoprenaline induced a significant decrease of R rs . An increase of R rs after administration of propranolol was observed but without any change of the frequency dependence of R rs . A small increase in the resonant frequency was also recorded. A decrease of R rs was recorded after yohimbine injection. Noradrenaline and xylazine administration increased the resistances and the resonant frequency and induced a negative frequency dependence of R rs . These results suggest that (1) the major effects of β adrenergic drugs are on the central airways, (2) the a adrenergic system may play a role on the regulation of bronchomotor tone in calves, (3) the effects of a adrenergic drugs are on both central and peripheral airways and (4) the forced oscillation technique allows the differentiation of calibre changes occurring in small and large airways.