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: CONCLUSIONS : The results give further support to the hypothesis that NO plays a role in motor behavior control and suggest that it may take part in the synaptic changes produced by antipsychotic treatment .
### Output Text:
CONCLUSIONS : The results give further support to the hypothesis that <span class="chemical">NO</span> plays a role in motor behavior control and suggest that it may take part in the synaptic changes produced by antipsychotic treatment . 