In vivo assessment of droperidol-induced bronchial relaxation in dogs using a superfine fibreoptic bronchoscope.
Droperidol has been reported to cause bronchodilatation but its mechanism(s) of action is unknown. We have evaluated the spasmolytic effect of droperidol on histamine- and serotonin (5-HT)-induced bronchoconstriction in dogs. Bronchial cross-sectional area was assessed with a superfine fibreoptic bronchoscope. Twenty-eight mongrel dogs were allocated randomly to one of two groups (histamine and 5-HT) to receive either histamine or 5-HT to induce bronchoconstriction. Changes in bronchial cross-sectional area were presented as percentage of basal bronchial cross-sectional area. Continuous i.v. infusion of histamine 500 micrograms kg-1 h-1 or 5-HT 500 micrograms kg-1 h-1 decreased percentage bronchial cross-sectional area by 46.4 (14.3)% or 68.9 (13.7)%, respectively. In both groups, droperidol reversed bronchoconstriction in a dose-dependent manner. In the histamine but not in the 5-HT group, plasma adrenaline and noradrenaline concentrations increased significantly after i.v. droperidol. In addition, propranolol antagonized droperidol-induced relaxation in the histamine but not in the 5-HT group. Our data indicate that the spasmolytic effect of droperidol on canine airway was caused, at least in part, by both catecholamine releases and 5-HT receptor antagonism.
Otomo
N
N
Department of Anaesthesiology, University of Hirosaki, School of Medicine, Japan.
Hirota
K
K
Sato
T
T
Hashimoto
Y
Y
Ishihara
H
H
D000818:Animals; D016084:Bronchoconstriction / Q000187:drug effects*; D001993:Bronchodilator Agents / Q000494:pharmacology*; D020680:Bronchoscopes; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004329:Droperidol / Q000494:pharmacology*; D005336:Fiber Optic Technology / Q000295:instrumentation; D006633:Histamine Antagonists / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology
D001993:Bronchodilator Agents; D006633:Histamine Antagonists; D012702:Serotonin Antagonists; D004329:Droperidol