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The α 2 ‐adrenoceptor agonists xylazine and guanfacine exert different central nervous system, but comparable peripheral effects in calves
Author(s) -
G Scholtysik,
F Régli,
Bruckmaier Rm,
Blum Jw
Publication year - 1998
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 - 10.1046/j.1365-2885.1998.00166.x
Subject(s) - guanfacine , xylazine , heart rate , endocrinology , medicine , pharmacodynamics , central nervous system , peripheral , sedation , sedative , pharmacology , chemistry , anesthesia , blood pressure , pharmacokinetics , clonidine , ketamine
Acute pharmacodynamic effects of the α 2 ‐adrenoceptor agonists, xylazine and guanfacine, were investigated in nine healthy calves in an open crossover trial. Xylazine (100 μg/kg body weight intravenously (i.v.)) and guanfacine (20 μg/kg body weight i.v.) were equi‐effective in lowering heart rate by 25–30% at 5 min. Under these conditions, xylazine induced strong sedation and increased plasma growth hormone levels, indicating central nervous system mediated actions, whereas guanfacine was not sedative and did not induce release of growth hormone. Oxygen consumption was decreased by both drugs, but respiratory exchange ratio decreased only in response to xylazine. However, in response to both drugs, plasma levels of noradrenaline, adrenaline, insulin and non esterified fatty acids decreased similarly and glucose increased comparably. These results demonstrate marked differences in the central nervous system‐mediated effects of the two α 2 ‐adrenoceptor agonists, whereas peripheral actions are similar.