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 contrast , SSR103800 failed to affect hyperactivity induced by amphetamine or naturally observed in dopamine transporter ( DAT ( - / - ) ) knockout mice ( 10 - 30 mg / kg p . o . ) .
### Output Text:
In contrast , <span class="chemical">SSR103800</span> failed to affect hyperactivity induced by <span class="chemical">amphetamine</span> or naturally observed in <span class="chemical">dopamine</span> transporter ( DAT ( - / - ) ) knockout mice ( 10 - 30 mg / kg p . o . ) . 