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: Moreover , naloxazone significantly attenuated the morphine - induced hypotension and respiratory depression , whereas morphine - induced bradycardia was less affected .
### Output Text:
Moreover , <span class="chemical">naloxazone</span> significantly attenuated the <span class="chemical">morphine</span> - induced hypotension and respiratory depression , whereas <span class="chemical">morphine</span> - induced bradycardia was less affected . 