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: On the other hand , nocistatin is recently isolated from the same precursor as nociceptin and blocks nociceptin - induced allodynia and hyperalgesia .
### Output Text:
On the other hand , <span class="chemical">nocistatin</span> is recently isolated from the same precursor as <span class="chemical">nociceptin</span> and blocks <span class="chemical">nociceptin</span> - induced allodynia and hyperalgesia . 