The vasomotor effects of 5-hydroxytryptamine on equine basilar arteries In vitro |
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Authors: | A Miyamoto T Obi A Nishio |
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Institution: | (1) Department of Veterinary Pharmacology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, 890 Kagoshima, Japan |
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Abstract: | The vasomotor effects of 5-hydroxytryptamine (5-HT) on isolated equine basilar arteries were studied. 5-HT induced contractions of equine basilar arteries in a concentration-dependent manner, with a pEC50 value (with 95% confidence limits) of 7.35 (7.08–7.62). Similar results were obtained with endothelium-denuded basilar arteries. Contractions were not competitively inhibited by the 5-HT2 receptor antagonist ketanserin at low concentrations of 5-HT. Conversely, at high concentrations of 5-HT, contractions were inhibited by ketanserin in a concentration-dependent manner, with a pA
2 value of 8.91 (8.62–9.20). The 5-HT1 and 5-HT2 receptor antagonist methiothepin shifted the concentration-response curve of 5-HT downwards and to the right in a concentration-dependent manner. In the presence of 10-6 mol/L ketanserin, however, methiothepin antagonized 5-HT-induced contractions competitively with a pA
2 value of 7.95 (7.59–8.31). The 5-HT3 receptor antagonist MDL 72222 had no effect on 5-HT-induced contractions. The findings of this study indicate that 5-HT1 and 5-HT2 receptors are located in equine basilar arterial smooth muscle cells, and that stimulation of these receptors results in contraction.Abbreviations CR
concentration ratio
- EC50
concentration producing 50% of the maximal response
- 5-HT
5-hydroxytryptamine
- MDL 72222
1H,3,5H-tropan-3-yl-3,5-dichlorobenzoate
- pA
2
negative logarithm of the molar concentration of antagonist that produces a 2-fold rightward shift of the concentration-response curve
- pEC50
negative logarithm of EC50
- PGF2
prostaglandin F2 |
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Keywords: | antagonists basilar artery horse 5-HT 5-hydroxytryptamine ketanserin MDL 72222 methiothepin serotonin smooth muscle |
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