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: Among these behavioral effects are decreases in food intake and decreases in amphetamine - induced locomotor activity .
### Output Text:
Among these behavioral effects are decreases in food intake and decreases in <span class="chemical">amphetamine</span> - induced locomotor activity . 