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: Therefore NFkappaB activity , oxidative stress , neuronal nitric oxide synthase ( nNOS ) activity , spatial learning and memory as well as the effect of topiramate , a previously proposed therapy for cocaine addiction , were evaluated in an experimental model of cocaine administration in rats .
### Output Text:
Therefore NFkappaB activity , oxidative stress , neuronal <span class="chemical">nitric oxide</span> synthase ( nNOS ) activity , spatial learning and memory as well as the effect of <span class="chemical">topiramate</span> , a previously proposed therapy for cocaine addiction , were evaluated in an experimental model of <span class="chemical">cocaine</span> administration in rats . 