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: Dopamine turnover ratios ( DOPAC : DA and HVA : DA ) were found to be lower in those animals exposed to the exploratory box when compared to their home cage counterparts .
### Output Text:
<span class="chemical">Dopamine</span> turnover ratios ( <span class="chemical">DOPAC</span> : <span class="chemical">DA</span> and <span class="chemical">HVA</span> : <span class="chemical">DA</span> ) were found to be lower in those animals exposed to the exploratory box when compared to their home cage counterparts . 