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: Responses of urinary strip preparations from control and cyclophosphamide - pretreated rats to electrical field stimulation and to agonists were assessed in the absence and presence of muscarinic , adrenergic and purinergic receptor antagonists .
### Output Text:
Responses of urinary strip preparations from control and <span class="chemical">cyclophosphamide</span> - pretreated rats to electrical field stimulation and to agonists were assessed in the absence and presence of muscarinic , adrenergic and purinergic receptor antagonists . 