In vitro responses of equine digital vessels to dopamine and fenoldopam.
Abstract: The in vitro responses of isolated vascular preparations of digital arteries and veins obtained from healthy anaesthetised horses were determined for dopamine and fenoldopam. The digital vessels were harvested, cut into 4 mm vascular segments, suspended in tissue baths and attached to force-displacement transducers. Dose-response studies between 10(-8) and 10(-4)M concentrations were performed for all drugs. The change in tension of each vascular ring was measured in grams of force. The reactivity between palmar and plantar digital vessels and baseline vascular responses were determined for dopamine. The vascular responses of dopamine were compared to in vitro data for other known vasoconstrictor agents. The mechanism of vasoconstriction induced by dopamine was further defined using prazosin, a specific competitive alpha-1 adrenoceptor antagonist. The vasodilating ability of fenoldopam, a dopamine-1 (DA-1) receptor agonist, was also determined using noradrenaline- preconstricted vascular segments from palmar digital vessels. The effective concentration to produce 50 per cent of the maximal response (EC50) and the maximal contraction in grams of force per milligram of the vascular ring (g/mg) were calculated. There were no differences in the reactivity between the palmar and plantar digital vessels. Dopamine produced intense constriction in arteries and veins but only at very high molar concentrations. Prazosin decreased significantly the sensitivity of the veins to dopamine (increased the mean EC50 values) but not the arteries. Prazosin had no effect on the maximal contractions of the vessels. Fenoldopam produced very little relaxation of either the arteries or veins. These results suggest that dopamine produces constriction in equine digital arteries and veins and that the constriction is only partially mediated by alpha-1 adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1991-01-01 PubMed ID: 1673099DOI: 10.1111/j.2042-3306.1991.tb02713.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research focuses on examining the in-vitro reactions of equine (horse) digital blood vessels to the substances dopamine and fenoldopam. Digital arteries and veins harvested from anaesthetised horses were used for this study.
Methodology
- The extracted digital blood vessels were cut into sections of 4 mm each and were suspended in tissue baths while being attached to force-displacement transducers.
- Researchers conducted dose-response studies using diverse concentrations of both dopamine and fenoldopam.
- The change in tension of each vascular ring was quantified in grams of force.
- The two compounds’ effects were also compared with other known vasoconstrictor agents.
- The research team examined the constriction induced by dopamine using prazosin, an antagonist that competes with alpha-1 adrenoceptors.
- The study also tested the potency of fenoldopam, a dopamine-1 (DA-1) receptor agonist, as a vasodilator on noradrenaline-preconstricted vascular segments from palmar, digital vessels.
- The team calculated the effective concentration that produced 50% of the maximal response (EC50) and the maximal contraction in force per milligram of the vascular ring (g/mg).
Findings
- The test found no significant reaction variations between the palmar and plantar digital vessels.
- Dopamine intensely constricted both arteries and veins but only at high molar concentrations.
- Prazosin notably reduced the veins’ sensitivity to dopamine, thus increasing the mean EC50 values, but it had no similar effect on the arteries.
- Prazosin did not influence the maximum constriction of the vessels.
- The experiment observed minimal vasodilation with the use of fenoldopam in both arteries and veins.
- All results from the study indicate that dopamine’s constriction in equine digital arteries and veins is only partially mediated by alpha-1 adrenoceptors.
This study provides new insight into the effects of dopamine and fenoldopam on the vasculature of equines. Understanding these interactions could be beneficial in advancing veterinary medicine and related therapies.
Cite This Article
APA
Baxter GM, Moore JN, Tackett RL.
(1991).
In vitro responses of equine digital vessels to dopamine and fenoldopam.
Equine Vet J, 23(1), 48-52.
https://doi.org/10.1111/j.2042-3306.1991.tb02713.x Publication
Researcher Affiliations
- Department of Large Animal Medicine, College of Veterinary Medicine, Athens, Georgia.
MeSH Terms
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / analogs & derivatives
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / pharmacology
- Animals
- Arteries / drug effects
- Dopamine / pharmacology
- Dose-Response Relationship, Drug
- Fenoldopam
- Forelimb
- Hindlimb
- Hoof and Claw / blood supply
- Horses / physiology
- Norepinephrine / pharmacology
- Prazosin / pharmacology
- Vasoconstriction / drug effects
- Vasodilator Agents / pharmacology
- Veins / drug effects
Citations
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