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 the present study , we tested the effects of i . c . v . injections of U - II on behavioral , metabolic , and endocrine responses in mice .
### Output Text:
In the present study , we tested the effects of i . c . v . injections of <span class="chemical">U - II</span> on behavioral , metabolic , and endocrine responses in mice . 