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: However , regardless of the duration of recovery ( and irrespective of either lesion volume , amphetamine dose , or post - lesion motor exercise ) , amphetamine - induced rotation tended to become gradually more ipsilateral as the observation session progressed , and all rats circled ipsilaterally to the lesion in response to further amphetamine injections .
### Output Text:
However , regardless of the duration of recovery ( and irrespective of either lesion volume , <span class="chemical">amphetamine</span> dose , or post - lesion motor exercise ) , <span class="chemical">amphetamine</span> - induced rotation tended to become gradually more ipsilateral as the observation session progressed , and all rats circled ipsilaterally to the lesion in response to further <span class="chemical">amphetamine</span> injections . 