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: Nociceptin / orphanin FQ and nocistatin on learning and memory impairment induced by scopolamine in mice .
### Output Text:
<span class="chemical">Nociceptin</span> / <span class="chemical">orphanin FQ</span> and <span class="chemical">nocistatin</span> on learning and memory impairment induced by <span class="chemical">scopolamine</span> in mice . 