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: Attenuation of methamphetamine - induced nigrostriatal dopaminergic neurotoxicity in mice by lipopolysaccharide pretreatment .
### Output Text:
Attenuation of <span class="chemical">methamphetamine</span> - induced nigrostriatal dopaminergic neurotoxicity in mice by <span class="chemical">lipopolysaccharide</span> pretreatment . 