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: The catalepsy induced by dopamine antagonists has been tested and the possible dopamine subtypes involved in catalepsy was determined .
### Output Text:
The catalepsy induced by <span class="chemical">dopamine</span> antagonists has been tested and the possible <span class="chemical">dopamine</span> subtypes involved in catalepsy was determined . 