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: In addition , PILO injected animals exhibited a reduction in the number of NPY - immunoreactive interneurons compared with controls .
### Output Text:
In addition , <span class="chemical">PILO</span> injected animals exhibited a reduction in the number of NPY - immunoreactive interneurons compared with controls . 