Given the broad range of functions that muscarinic receptors subserve, it is of fundamental importance to find subtype-selective ligands for therapeutic use in specific disorders. Antagonists with long-residence time at receptors are acting longer which allows for a lower daily dose to reach a maximal therapeutic effect. A fundamentally novel class of antagonists are PAM-antagonists that exert positive cooperativity with endogenous neurotransmitter. PAM-antagonists preferentially block activated receptors. PAM-antagonists of muscarinic receptors have a therapeutic potential in a selective reversal of persistent excessive agonism under certain pathological conditions, like bronchospasm in asthma. We aim to delineate the molecular mechanisms underlying long-residence time and PAM-antagonism. Based on this knowledge we will design novel long-acting PAM-antagonists.