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: 4 - DAMP inhibited the tonic contractions in controls more potently than methoctramine and pirenzepine .
### Output Text:
<span class="chemical">4 - DAMP</span> inhibited the tonic contractions in controls more potently than <span class="chemical">methoctramine</span> and <span class="chemical">pirenzepine</span> . 