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 .
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