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: Anticonvulsant actions of MK - 801 on the lithium - pilocarpine model of status epilepticus in rats .
### Output Text:
Anticonvulsant actions of <span class="chemical">MK - 801</span> on the <span class="chemical">lithium</span> - <span class="chemical">pilocarpine</span> model of status epilepticus in rats . 