In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: In inflamed preparations , the muscarinic receptor antagonism on the phasic component of the electrical field stimulation - evoked contraction was decreased and the pirenzepine and 4 - DAMP antagonism on the tonic component was much less efficient than in controls .
### Output Text:
In inflamed preparations , the muscarinic receptor antagonism on the phasic component of the electrical field stimulation - evoked contraction was decreased and the <span class="chemical">pirenzepine</span> and <span class="chemical">4 - DAMP</span> antagonism on the tonic component was much less efficient than in controls . 