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Does segmental difference in alpha 1-adrenoceptor subtype explain contractile difference in rat abdominal and
Juan Asbún-Bojalil1, Enrique F Castillo, Bruno A Escalante
1Sección de Estudios de Posgrado e Investigación de la Escuela Superior de Medicina, IPN Plan de San Luis y Díaz Mirón, Col. Casco de Sto. Tomás, 17, Mexico 11340, DF, Mexico.
Vascular Pharmacology
|October 31, 2002
Summary
Indomethacin affects rat aorta constriction differently based on location. This study suggests both abdominal and thoracic aortas use the same alpha 1D-adrenoceptor (AR) subtype for phenylephrine-induced contractions.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Adrenoceptor Research
Background:
- Segmental differences in rat aorta function are observed, particularly regarding cyclooxygenase inhibitor effects on adrenergic agonist responses.
- The role of specific alpha 1-adrenoceptor (AR) subtypes in mediating aortic contractions requires further elucidation.
Purpose of the Study:
- To investigate potential segmental differences in alpha 1-adrenoceptor (AR) subtypes within the rat aorta.
- To explain the differential effect of indomethacin on adrenergic agonist-induced contractions in rat abdominal versus thoracic aorta.
Main Methods:
- Utilized endothelium-denuded rat thoracic and abdominal aortic rings.
- Administered phenylephrine to assess concentration-dependent contractions.
- Investigated the effects of indomethacin and selective alpha 1-AR antagonists (BMY 7378, prazosin, 5-methylurapidil, WB 4101) on phenylephrine-induced contractions.
Main Results:
- Phenylephrine elicited similar contractions in both abdominal and thoracic aorta rings.
- Indomethacin inhibited phenylephrine-induced contractions only in the abdominal aorta.
- Selective alpha 1D-AR antagonist BMY 7378 competitively antagonized phenylephrine contractions in both aorta segments with similar affinities.
- Prazosin, 5-methylurapidil, and WB 4101 also demonstrated competitive antagonism consistent with alpha 1D-AR subtype mediation in both aorta regions.
Conclusions:
- The contraction of rat abdominal and thoracic aorta to phenylephrine is mediated by the same alpha 1D-adrenoceptor (AR) subtype.
- Segmental differences in indomethacin's effect are not explained by distinct alpha 1-AR subtypes but may involve other mechanisms.