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Apomorphine‐induced emesis in the dog‐routes of administration, efficacy and synergism by naloxone
Author(s) -
SCHERKL R.,
HASHEM A.,
FREY H.H.
Publication year - 1990
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.1365-2885.1990.tb00763.x
Subject(s) - apomorphine , (+) naloxone , pharmacology , vomiting , medicine , stimulation , antagonist , anesthesia , receptor , chemistry , agonist
Scherkl, R., Hashem, A. & Frey, H.‐H. Apomorphine‐induced emesis in the dog‐routes of administration, efficacy and synergism by naloxone. J. vet. Pharmacol. Therap. 13, 154–158. Apomorphine proved to be more effective as an emetic in dogs after s.c. administration than after i.m. injection with doses of 0.04 and 0.1 mg/kg. This effect is explained by an anti‐emetic effect mediated by μ‐receptors in the vomiting centre in die brain, which, in contrast to the chemoreceptor trigger zone, is within the blood‐brain barrier. A certain delay between the stimulation of D 2 ‐receptors in the chemoreceptor trigger zone (causing emesis) and μ‐receptors in the vomiting centre (producing anti‐emesis) therefore results, leading to a self‐limiting emesis. Blockade of the μ‐receptors by naloxone increased and prolonged the effect of apomorphine. A relatively narrow range of apomorphine concentrations on s.c. administration is then effective to stimulate the chemoreceptor trigger zone, but can hardly inhibit the vomiting centre, and must therefore be considered the most suitable route for administration of apomorphine. R. Scherkl, Department of Pharmacology and Toxicology, School of Veterinary Medicine, Free University of Berlin, Koserstr. 20, D‐1000, West Berlin, FRG.