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 influence of adenosine receptor agonists and antagonists on cocaine - and amphetamine - induced hyperactivity was examined in mice .
### Output Text:
The influence of <span class="chemical">adenosine</span> receptor agonists and antagonists on <span class="chemical">cocaine</span> - and <span class="chemical">amphetamine</span> - induced hyperactivity was examined in mice . 