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: IT MK - 801 significantly reduced the number of dark - stained alpha - motoneurons after morphine - induced spastic paraparesis compared with the saline group .
### Output Text:
IT <span class="chemical">MK - 801</span> significantly reduced the number of dark - stained alpha - motoneurons after <span class="chemical">morphine</span> - induced spastic paraparesis compared with the saline group . 