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: Given that apomorphine inhibits passive avoidance retention when given during training or in a defined 10 - 12h post - training period , we evaluated the ability of nefiracetam to attenuate amnesia induced by dopaminergic agonism .
### Output Text:
Given that <span class="chemical">apomorphine</span> inhibits passive avoidance retention when given during training or in a defined 10 - 12h post - training period , we evaluated the ability of <span class="chemical">nefiracetam</span> to attenuate amnesia induced by dopaminergic agonism . 