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: Nitric oxide ( NO ) , gaseous neurotransmitter , has contradictor role in epileptogenesis due to opposite effects of L - arginine , precursor of NO syntheses ( NOS ) , and L - NAME ( NOS inhibitor ) observed in different epilepsy models .
### Output Text:
<span class="chemical">Nitric oxide</span> ( <span class="chemical">NO</span> ) , gaseous neurotransmitter , has contradictor role in epileptogenesis due to opposite effects of <span class="chemical">L - arginine</span> , precursor of <span class="chemical">NO</span> syntheses ( NOS ) , and <span class="chemical">L - NAME</span> ( NOS inhibitor ) observed in different epilepsy models . 