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: Post - training administration of naloxone ( 3 mg / kg ) as a single or as a split dose also attenuated the scopolamine - induced amnesia .
### Output Text:
Post - training administration of <span class="chemical">naloxone</span> ( 3 mg / kg ) as a single or as a split dose also attenuated the <span class="chemical">scopolamine</span> - induced amnesia . 