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Reactivity of Equine Palmar Digital Arteries and Veins to Vasodilating Agents
Author(s) -
BAXTER GARY M.,
TACKETT RANDALL L.,
MOORE JAMES N.
Publication year - 1989
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.1989.tb01075.x
Subject(s) - acepromazine , medicine , vasodilation , prostacyclin , norepinephrine , acetylcholine , endocrinology , anesthesia , blood pressure , heart rate , dopamine
Palmar digital arteries and veins removed surgically from healthy horses under general anesthesia were cut into 4 mm vascular rings, suspended in tissue baths, and attached to force displacement transducers for continuous measurement of vascular tension. In vitro vascular responses were determined for acetylcholine, acepromazine, isoxsuprine hydrochloride (isoxsuprine), prostaglandin E 2 (PGE 2 ), and prostaglandin I 2 (prostacyclin). After preconstriction with norepinephrine hydrochloride (norepinephrine), or prostaglandin F 2 alpha (PGF 2 alpha), the concentrations needed to produce 50% maximum relaxation (EC 50 ) and the maximum percentage of relaxation were determined for each drug. Acetylcholine was the most potent arterial vasodilator (smallest EC 50 value) and PGE 2 was the least potent. Prostacyclin was the least potent venodilator (highest EC 50 value); there were no differences between acetylcholine, acepromazine, isoxsuprine, and PGE 2 . Isoxsuprine produced greater arterial relaxation than all other agents. Isoxsuprine and acepromazine produced significantly greater venous relaxation than did acetylcholine and PGE 2 . Prostacyclin produced minimal vasodilation of arteries or veins. Acepromazine and isoxsuprine relaxed the veins significantly more than the arteries. When PGF 2 alpha was used instead of norepinephrine to preconstrict the arteries and veins, the potency and effectiveness of acepromazine and isoxsuprine to produce vasodilation were significantly decreased. Results indicate that acepromazine and isoxsuprine can relax the equine digital vasculature but their effectiveness varies depending on the origin of the constriction.