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: Anesthetized rats received the tricyclic antidepressant desipramine IP to produce hypotension , QRS prolongation , and bradycardia .
### Output Text:
Anesthetized rats received the tricyclic antidepressant <span class="chemical">desipramine</span> IP to produce hypotension , QRS prolongation , and bradycardia . 