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: However , the increased rearings and the amphetamine - induced stereotypies were not blocked by pretreatment with DSP4 .
### Output Text:
However , the increased rearings and the <span class="chemical">amphetamine</span> - induced stereotypies were not blocked by pretreatment with <span class="chemical">DSP4</span> . 