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: The serotonin - 1A receptor agonist , 8 - OH - DPAT , induced a significant disruption of PPI in all groups .
### Output Text:
The <span class="chemical">serotonin</span> - 1A receptor agonist , <span class="chemical">8 - OH - DPAT</span> , induced a significant disruption of PPI in all groups . 