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: Administration of graded doses of U - II ( 1 - 10 , 000 ng / mouse ) provoked : ( 1 ) a dose - dependent reduction in the number of head dips in the hole - board test ; ( 2 ) a dose - dependent reduction in the number of entries in the white chamber in the black - and - white compartment test , and in the number of entries in the central platform and open arms in the plus - maze test ; and ( 3 ) a dose - dependent increase in the duration of immobility in the forced - swimming test and tail suspension test .
### Output Text:
Administration of graded doses of <span class="chemical">U - II</span> ( 1 - 10 , 000 ng / mouse ) provoked : ( 1 ) a dose - dependent reduction in the number of head dips in the hole - board test ; ( 2 ) a dose - dependent reduction in the number of entries in the white chamber in the black - and - white compartment test , and in the number of entries in the central platform and open arms in the plus - maze test ; and ( 3 ) a dose - dependent increase in the duration of immobility in the forced - swimming test and tail suspension test . 