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: Regional localization of the antagonism of amphetamine - induced hyperactivity by intracerebral calcitonin injections .
### Output Text:
Regional localization of the antagonism of <span class="chemical">amphetamine</span> - induced hyperactivity by intracerebral <span class="chemical">calcitonin</span> injections . 