Key result
Alpha-2-adrenoceptor agonists and antagonists did not induce changes in aggregation of bovine or equine platelets or potentiate ADP- or collagen-induced platelet aggregation.
Commonly used α(2)-adrenoceptor agonists (xylazine, medetomidine) and antagonists (tolazoline, atipamezole) do not adversely affect platelet function in cattle and horses.
Answers are grounded in this paper and cite their sources.
Supports lack of platelet effects for these agents in cattle and horses; leaves open in vivo hemostatic implications.
OBJECTIVE: To investigate effects of various imidazoline and nonimidazoline α-adrenergic agents on aggregation and antiaggregation of bovine and equine platelets. SAMPLE: Blood samples obtained from 8 healthy adult cattle and 16 healthy adult Thoroughbreds. PROCEDURES: Aggregation and antiaggregation effects of various imidazoline and nonimidazoline α-adrenergic agents on bovine and equine platelets were determined via a turbidimetric method. Collagen and ADP were used to initiate aggregation. RESULTS: Adrenaline, noradrenaline, or α-adrenoceptor agents alone did not induce changes in aggregation of bovine or equine platelets or potentiate ADP- or collagen-induced platelet aggregation. Adrenaline and the α(2)-adrenoceptor agonist clonidine had an inhibitory effect on ADP- and collagen-induced aggregation of bovine platelets. The α(2)-adrenoceptor antagonists phentolamine and yohimbine also inhibited collagen-induced aggregation of bovine platelets. Noradrenaline, other α-adrenoceptor agonists (xylazine, oxymetazoline, and medetomidine), and α-adrenoceptor antagonists (atipamezole, idazoxan, tolazoline, and prazosin) were less effective or completely ineffective in inhibiting ADP- and collagen-induced aggregation of bovine platelets. The imidazoline α(2)-adrenoceptor agonist oxymetazoline submaximally inhibited collagen-induced aggregation of equine platelets, and the α(2)-adrenoceptor antagonist idazoxan, along with phentolamine and yohimbine, also inhibited collagen-induced aggregation of equine platelets. The imidazoline compound antazoline inhibited both ADP- and collagen-induced aggregation of equine platelets. CONCLUSIONS AND CLINICAL RELEVANCE: Several drugs had effects on aggregation of platelets of cattle and horses, and effective doses of ADP and collagen also differed between species. The α(2)-adrenoceptor agonists (xylazine and medetomidine) and antagonists (tolazoline and atipamezole) may be used by bovine and equine practitioners without concern for adverse effects on platelet function and hemostasis.
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Yokota et al. (2013) studied Healthy (n=24). Imidazoline and nonimidazoline alpha-adrenergic agents was evaluated on Platelet aggregation and antiaggregation. Alpha-2-adrenoceptor agonists and antagonists did not induce changes in aggregation of bovine or equine platelets or potentiate ADP- or collagen-induced platelet aggregation.
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