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: CONCLUSION : The administration of CaCl2 or 4 - aminopyridine did not reverse tricyclic antidepressant - induced hypotension in rats .
### Output Text:
CONCLUSION : The administration of <span class="chemical">CaCl2</span> or <span class="chemical">4 - aminopyridine</span> did not reverse tricyclic antidepressant - induced hypotension in rats . 