Two relaxation-mediating P2-purinoceptors in guinea-pig taenia caeci

• Published in: Naunyn-Schmiedeberg's archives of pharmacology 1995-01, Vol.351 (1), p.107-110
• Main Authors: Dudeck, O, Bültmann, R, Starke, K
• Format: Article
• Language: English
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Animals; Cecum - drug effects; Cecum - physiology; Dose-Response Relationship, Drug; Female; Guinea Pigs; In Vitro Techniques; Male; Muscle Relaxation - drug effects; Muscle Relaxation - physiology; Receptors, Purinergic P2 - drug effects; Receptors, Purinergic P2 - physiology
• ISSN: 0028-1298; 1432-1912
• DOI: 10.1007/bf00169071

2-Methylthio ATP, noradrenaline, adenosine 5'-O-(2-thiodiphosphate) (ADP beta S), alpha, beta-methylene ATP, ATP and adenosine caused relaxation of guinea-pig isolated taenia caeci precontracted by carbachol, with potency decreasing in the order indicated. 4,4'-Diisothiocyanatostilbene-2,2'-disulphonate (DIDS) 10, 32 and 100 microM shifted the concentration-response curve of alpha, beta-methylene ATP increasingly to the right, by the factor 141 at DIDS 100 microM. Concentration-response curves of the other agonists were not shifted to the right by DIDS 100 microM, except for the curve of ADP beta S which was shifted by the factor 2.4. The relaxation produced by 2-methylthio ATP faded rapidly. When the fade was complete, further addition of 2-methylthio ATP or ATP did not elicit relaxation, whereas the relaxant effect of alpha, beta-methylene ATP was unchanged. The results indicate that there are at least two relaxation-mediating P2-purinoceptors in guinea-pig taenia caeci, the P2Y-purinoceptor which is relatively insensitive to DIDS and a distinct receptor for alpha, beta-methylene ATP which is very sensitive to DIDS.