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: However , temperature effects of drugs that have been used to manipulate brain DA neurotransmission confound interpretation of the data .
### Output Text:
However , temperature effects of drugs that have been used to manipulate brain <span class="chemical">DA</span> neurotransmission confound interpretation of the data . 