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: In this study , we investigated whether increased generation of FR during status epilepticus would be sufficient to provoke abnormalities in mtDNA and in the expression and activity of cytochrome c oxidase ( CCO ) , complex IV of the respiratory chain , in the chronic phase of the pilocarpine model of temporal lobe epilepsy .
### Output Text:
In this study , we investigated whether increased generation of FR during status epilepticus would be sufficient to provoke abnormalities in mtDNA and in the expression and activity of cytochrome c oxidase ( CCO ) , complex IV of the respiratory chain , in the chronic phase of the <span class="chemical">pilocarpine</span> model of temporal lobe epilepsy . 