tokens: The muscarinic receptor antagonists atropine , 4 - diphenylacetoxy - N - methylpiperidine ( 4 - DAMP ) ( ' M ( 1 ) / M ( 3 ) / M ( 5 ) - selective ' ) , methoctramine ( ' M ( 2 ) - selective ' ) and pirenzepine ( ' M ( 1 ) - selective ' ) antagonized the tonic component of the electrical field stimulation - evoked contractile response more potently than the phasic component .