Abstract

Muscarinic receptors (M1-M5) are G-protein coupled receptors found in the plasma membrane. Muscarinic antagonists are selective for smooth muscle muscarinic sites and are widely used in the treatment of various diseases such as asthma and chronic obstructive pulmonary disorders. However, these anti-cholinergics have been associated with various side effects. The aim of the investigation was to determine the effects of individual muscarinic receptor antagonists in the setting of myocardial ischaemia reperfusion injury. A Langendorff perfusion system was used to perfuse isolated hearts which were subjected to 35 min of ischaemia followed by 120 min of reperfusion in the presence and absence of individual muscarinic antagonists Telenzepine (1 nM–1000 nM), AF-DX 116 (1 nM–3000 nM) and DAU 5884 (1 nM–3000 nM) (M1, M2 and M3, respectively) which were added throughout reperfusion. Results showed that administration of Telenzepine increased the infarct size significantly only at the highest concentration. The administration of AF-DX 116 and DAU 5884 significantly increased the infarct size to RR with maximum infarction being achieved at the concentration of 1000 nM for both the drugs. This is the first study to identify the detrimental effects of specific subtypes of muscarinic receptor antagonists in the context of myocardial ischaemia reperfusion injury. We are currently investigating the precise biological mechanisms by which these anti-cholinergics increase the risk of adverse cardiovascular outcomes.