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: Treatment with amantadine did not alter whole brain dopamine levels but decreased the amounts of 3 , 4 - dihydroxyphenylacetic acid in the BALB / C mice compared to saline control .
### Output Text:
Treatment with <span class="chemical">amantadine</span> did not alter whole brain <span class="chemical">dopamine</span> levels but decreased the amounts of <span class="chemical">3 , 4 - dihydroxyphenylacetic acid</span> in the BALB / C mice compared to saline control . 