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: These results suggest that activation of NMDA receptors plays an important role in status epilepticus and brain damage in the lithium - pilocarpine model .
### Output Text:
These results suggest that activation of <span class="chemical">NMDA</span> receptors plays an important role in status epilepticus and brain damage in the <span class="chemical">lithium</span> - <span class="chemical">pilocarpine</span> model . 