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: All adenosine receptor agonists significantly decreased the locomotor activity in mice , and the effects were dose - dependent .
### Output Text:
All <span class="chemical">adenosine</span> receptor agonists significantly decreased the locomotor activity in mice , and the effects were dose - dependent . 