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: Combination of SKF 38393 with quinpirole did not cause potentiated inhibitory effect on catalepsy induced by dopamine antagonists .
### Output Text:
Combination of <span class="chemical">SKF 38393</span> with <span class="chemical">quinpirole</span> did not cause potentiated inhibitory effect on catalepsy induced by <span class="chemical">dopamine</span> antagonists . 