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: Fos - IR in the spinal cord was not changed in rats receiving chronic CYP treatment ( n = 15 , 75 mg / kg , i . p . , every 3rd day for 2 weeks ) .
### Output Text:
Fos - IR in the spinal cord was not changed in rats receiving chronic <span class="chemical">CYP</span> treatment ( n = 15 , 75 mg / kg , i . p . , every 3rd day for 2 weeks ) . 