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: NO - induced migraine attack : strong increase in plasma calcitonin gene - related peptide ( CGRP ) concentration and negative correlation with platelet serotonin release .
### Output Text:
<span class="chemical">NO</span> - induced migraine attack : strong increase in plasma <span class="chemical">calcitonin gene - related peptide</span> ( <span class="chemical">CGRP</span> ) concentration and negative correlation with platelet <span class="chemical">serotonin</span> release . 