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: These data indicate that IT morphine induces spastic paraparesis with a concomitant increase in CSF glutamate , which is involved in NMDA receptor activation .
### Output Text:
These data indicate that IT <span class="chemical">morphine</span> induces spastic paraparesis with a concomitant increase in CSF <span class="chemical">glutamate</span> , which is involved in <span class="chemical">NMDA</span> receptor activation . 