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Relaxation of equine tracheal muscle in vitro by different adrenoceptor drugs
Author(s) -
TÖRNEKE K.,
LARSSON C. INGVAST,
APPELGREN L. E.
Publication year - 1997
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.1365-2885.1997.tb00098.x
Subject(s) - clenbuterol , isometric exercise , isoprenaline , carbachol , potency , endocrinology , medicine , contraction (grammar) , chemistry , muscle relaxation , mean value , population , receptor , in vitro , stimulation , mathematics , biochemistry , statistics , environmental health
Strips of tracheal smooth muscle from 12 horses were contracted by carbachol in tissue baths under isometric conditions. This contraction (≅50% of maximum: EC 50 ) was relaxed completely with adrenoceptor drugs. The only exception was clenbuterol, where the degree of relaxation was ≅90%. In all horses the EC 50 ‐value for isoprenaline (mean 1.6 × 10 −8 M) was less than that for adrenaline (mean 9.6 × 10 − 8 M) and noradrenaline (mean 1. 8 × 10 ‐ 6 M). The potency ratio was 1 < 6 < 110 which indicates that the β 2 ‐subtype dominates among the β‐adrenoceptors of equine airways. All preparations were also very sensitive to the specific and potent β 2 ‐receptor agonists clenbuterol (mean 5.7 × 10 − 9 M) and procaterol (mean 3.6 × 10 −10 M). No differences in EC 50 ‐values due to age, sex and breed were observed in this material. The standard deviation of the mean EC 50 ‐values seems to be larger for the specific β 2 ‐adrenoceptor agonists than for the unspecific. A reason for this could be differences in the pattern of the β‐adrenoceptor population.