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: NFkappaB activity was decreased in the frontal cortex of cocaine treated rats , as well as GSH concentration and glutathione peroxidase activity in the hippocampus , whereas nNOS activity in the hippocampus was increased .
### Output Text:
NFkappaB activity was decreased in the frontal cortex of <span class="chemical">cocaine</span> treated rats , as well as <span class="chemical">GSH</span> concentration and <span class="chemical">glutathione</span> peroxidase activity in the hippocampus , whereas nNOS activity in the hippocampus was increased . 