BACKGROUND AND PURPOSE: The aim of this study was to develop potent and long-acting antagonists of muscarinic ACh receptors. The 4-hexyloxy and 4-butyloxy derivatives of 1-[2-(4-oxidobenzoyloxy)ethyl]-1,2,3,6-tetrahydropyridin-1-ium were synthesized and tested for biological activity. Antagonists with long-residence time at receptors are therapeutic targets for the treatment of several neurological and psychiatric human diseases. Their long-acting effects allow for reduced daily doses and adverse effects. EXPERIMENTAL APPROACH: The binding and antagonism of functional responses to the agonist carbachol mediated by 4-hexyloxy compounds were investigated in CHO cells expressing individual subtypes of muscarinic receptors and compared with 4-butyloxy analogues. KEY RESULTS: The 4-hexyloxy derivatives were found to bind muscarinic receptors with micromolar affinity and antagonized the functional response to carbachol with a potency ranging from 30 nM at M1 to 4 μM at M3 receptors. Under washing conditions to reverse antagonism, the half-life of their antagonistic action ranged from 1.7 h at M2 to 5 h at M5 receptors. CONCLUSIONS AND IMPLICATIONS: The 4-hexyloxy derivatives were found to be potent long-acting M1 -preferring antagonists. In view of current literature, M1 -selective antagonists may have therapeutic potential for striatal cholinergic dystonia, delaying epileptic seizure after organophosphate intoxication or relieving depression. These compounds may also serve as a tool for research into cognitive deficits.

• MeSH
• Muscarinic Antagonists chemical synthesis   chemistry   pharmacology   MeSH
• CHO Cells MeSH
• Cricetulus MeSH
• Carbachol chemistry   pharmacology   MeSH
• Cells, Cultured MeSH
• Molecular Structure MeSH
• Pyridines chemical synthesis   chemistry   pharmacology   MeSH
• Receptors, Muscarinic metabolism   MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Muscarinic Antagonists MeSH
• Carbachol MeSH
• Pyridines MeSH
• Receptors, Muscarinic MeSH

Xanomeline is an agonist endowed with functional preference for M1/M4 muscarinic acetylcholine receptors. It also exhibits both reversible and wash-resistant binding to and activation of these receptors. So far the mechanisms of xanomeline selectivity remain unknown. To address this question we employed microfluorometric measurements of intracellular calcium levels and radioligand binding to investigate differences in the short- and long-term effects of xanomeline among muscarinic receptors expressed individually in Chinese hamster ovary cells. 1/One-min exposure of cells to xanomeline markedly increased intracellular calcium at hM1 and hM4, and to a lesser extent at hM2 and hM3 muscarinic receptors for more than 1 hour. 2/Unlike the classic agonists carbachol, oxotremorine, and pilocarpine 10-min exposure to xanomeline did not cause internalization of any receptor subtype. 3/Wash-resistant xanomeline selectively prevented further increase in intracellular calcium by carbachol at hM1 and hM4 receptors. 4/After transient activation xanomeline behaved as a long-term antagonist at hM5 receptors. 5/The antagonist N-methylscopolamine (NMS) reversibly blocked activation of hM1 through hM4 receptors by xanomeline. 6/NMS prevented formation of xanomeline wash-resistant binding and activation at hM2 and hM4 receptors and slowed them at hM1, hM3 and hM5 receptors. Our results show commonalities of xanomeline reversible and wash-resistant binding and short-time activation among the five muscarinic receptor subtypes. However long-term receptor activation takes place in full only at hM1 and hM4 receptors. Moreover xanomeline displays higher efficacy at hM1 and hM4 receptors in primary phasic intracellular calcium release. These findings suggest the existence of particular activation mechanisms specific to these two receptors.

• MeSH
• Cyclic AMP metabolism   MeSH
• Cell Membrane drug effects   metabolism   MeSH
• Time Factors MeSH
• CHO Cells MeSH
• Cricetulus MeSH
• Extracellular Space drug effects   metabolism   MeSH
• Intracellular Space drug effects   metabolism   MeSH
• Kinetics MeSH
• Cricetinae MeSH
• Humans MeSH
• N-Methylscopolamine pharmacology   MeSH
• Pyridines pharmacology   MeSH
• Receptor, Muscarinic M1 agonists   antagonists & inhibitors   metabolism   MeSH
• Receptor, Muscarinic M4 agonists   antagonists & inhibitors   metabolism   MeSH
• Thiadiazoles pharmacology   MeSH
• Calcium metabolism   MeSH
• Binding Sites drug effects   MeSH
• Animals MeSH
• Check Tag
• Cricetinae MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cyclic AMP MeSH
• N-Methylscopolamine MeSH
• Pyridines MeSH
• Receptor, Muscarinic M1 MeSH
• Receptor, Muscarinic M4 MeSH
• Thiadiazoles MeSH
• Calcium MeSH
• xanomeline MeSH Browser