Ahmet AKICI, Şule OKTAY, Arthur CHRİSTOPOULOS, Muradiye NACAK

Darifenacin reveals a functional role for M4 muscarinic acetylcholine receptors in guinea pig gallbladder

Objective: Previous studies have revealed the presence of M1 to M4 muscarinic receptors in guinea pig gallbladder, with M3 and M4 receptors being claimed to mediate contractions. Methods: In the present study, cumulative concentration-response curves to carbachol were constructed in the absence and presence of darifenacin, which has greater selectivity for M3 over M4 receptors, in guinea-pig gallbladder. Results: Darifenacin caused concentration-dependent dextral shifts of the carbachol curve, however, at 1 jiM, it also caused a degree of insurmountable antagonism. Using a novel analytical approach, we obtained a pKB estimate for darifenacin (7.51 ± 0.14) that is in excellent agreement with its affinity for M2/M4, but not M3 receptors. Conclusion: Given our previous demonstration that M2 receptors are unlikely to contribute to muscarinic contractions in this tissue, our current findings provide pharmacological evidence for a predominant role of M4 muscarinic receptors in guinea pig gallbladder contractions.

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1. Caufield MP, Birdsall tiJM. International Union of Pharmacology. XVII: Classification of muscarinic acetylcholine receptors. Pharmacol Rev 1998;50:279-290. 2. Eglen RM, Reddy II, Watson N, Challiss RAJ. Muscarinic acetylcholine receptor subtypes in smooth muscle. Trends Pharmacol Sci 1994;15:114-119. 3. Eltze M, König H, Ullrich B, Grebe T. Contraction of guinea-pig gallbladder: muscarinic M3 or M4 receptors? Eur J Pharmacol 1997:332:77-87. 4. Takahashi T, Kurosawa S, Owyang C. Regulation of PI hydrolysis and cAMP formation by muscarinic M5 receptor in guinea-pig gallbladder. Am J Physiol 1994; 267:0523-0528.
5. Von Schrenck T, SieversJ, Mirau S, Raedler A, Qreten H. Characterization of muscarinic receptors on guinea-pig gallbladder smooth muscle. Qastroenterology 1993; 105:1341- 1349. 6. Von Schrenck T, Mackensen B, Mende U, et al. Signal transduction pathway of the muscarinic receptors mediating gallbladder contraction. riaunyn-Schmfed. Arch Pharmacol 1994;349: 346-354. 7. Özkutîu U, Alican I, Karahan F, et al. Are m- cholinoceptors of guinea-pig gallbladder smooth muscle of m4 subtype? Pharmacology 1993;46:308-314. 8. Oktay Ş, Cabadak H, İskender E, et al. Evidence for the presence of muscarinic M2 and M4 receptors in guinea-pig gallbladder smooth muscle. J Auton Pharmacol 1998; 18:195-204. 9. Parkman HP, Pagano AP, Ryan JP. Subtypes of muscarinic receptors regulating gallbladder cholinergic contractions. Am J Physiol 1999:84:71-76.
10. Karaalp A, Akıcı A, Akbulut ti, Ulusoy NB, Oktay Ş. Distinct functional muscarinic receptors in guinea-pig gallbladder, ileum and atria. Pharmacol Res 1999:39:389-395. 11. Akıcı A, Karaalp, A, İskender E, Christopoulus A, El-Fakahany EE, Oktay Ş. Further evidence for the heterogeneity of functional muscarinic receptors in guinea-pig gallbladder. Eur J Pharmacol 2000,-388:115-123. 12. Alabaster VA. Discovery and development of selective M3 antagonists for clinical use. Life Sci 1997:60:1053-1060. 13. Wallis RM, Napier CM. Muscarinic antagonists in development for disorders of smoothe muscle function. Life Sci 1999:64:395-401. 14. Christopoulos A, Parsons AM, Lew MJ, El- Fakahany EE. The assessment of antagonist potency under conditions of transient response kinetics. Eur J Pharmacol 1999; 382:217-227. 15. Christopoulos A, Coles P, LayL, Lew MJ, Angus JA. Pharmacological analysis of cannabinoid receptor activity in the rat vas deferens. Br J Pharmac 2001:132:1281-1291. 16. Christopoulos A. From captive agonism to insurmountable antagonism: Demonstrating the power of analytical pharmacology. Clin Exp Pharmacol Physiol 2001:28:223-229. 17. Lew MJ, Angus. Analysis of competitive agonist-antagonist interactions by nonlinear regression. Trends Pharmacol Sci 1995:16:328-337. 18. Van Charldorp KJ, Van Zwieten PA. Comparison of the muscarinic receptors in the coronary artery, cerebral artery and atrium of the pig, riaunyn-Schmied. Arch Pharmacol 1989/339:403-408. 19. Doods fin, Willim KD, Boddeke fiWGM, Entzeroth M. Characterization of muscarinic receptors in guinea-pig uterus. Eur J Pharmacol 1993,-250:223-230. 20. Eğlen RM, Michel AD, Whiting RL. Characterization of the muscarinic receptor subtype mediating contractions of the guinea- pig uterus. BrJ Pharmacol 1989; 96:497-499. 21. Eglen RM, Michel AD, Levine WB, Whiting RL. Analysis of muscarinic receptors in guinea-pig estrogen-dominated uterus, in vitro. Br J Pharmacol 1991;104:44P. 22. Eglen RM, Whiting RL. Heterogeneity of vascular muscarinic receptors. J Auton Pharmacol 1990; 10:233-245. 23. Chen Q, Yu P, De Petris Q, Biancani P, Behar J. Distinct muscarinic receptors and signal transduction pathways in gallbladder muscle. J Pharmacol Exp Ther 1995:273:650- 655. 24. fleinig T, Von Schrenck T, De Weerth A, Kölsch K, Schultz M, Izbicki JR. Characterization of gallbladder muscarinic receptor subtypes: Signal transduction and
Qastroenterology RT-PCR studies. 1997,-112:746. 25. Choppin A, Eglen RM. Pharmacological characterization of muscarinic receptors in dog isolated ciliary and urinary bladder smooth muscle. Br J Pharmacol 2001;132:835-842. 26. Choppin A, Eglen RM, Pharmacological characterization of muscarinic receptors in mouse isolated urinary bladder smooth muscle. Br J Pharmacol 2001,-133:1035- 1040. 27. Choppin A, Eglen RM, Hedge SS. Pharmacological characterisation of muscarinic receptors in rabbit isolated iris sphincter muscle and urinary bladder smooth muscle. Br J Pharmacol 1998;124:883-888. 28. Hedge SS, Choppin A, Bonhaus D, et al. Functional role of M2 and M3 muscarinic receptors in the urinary bladder of rats in vitro and in vivo. Br J Pharmacol 1997; 120:1409- 1418. 29. Yamanishi T., Chappie CR, Yasuda K, Chess- Williams R. The role of M2-muscarinic receptors in mediating contraction of the pig urinary bladder in vitro. Br J Pharmacol 2000,-131:1482-1488.