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: Protective efficacy of neuroactive steroids against cocaine kindled - seizures in mice .
### Output Text:
Protective efficacy of neuroactive <span class="chemical">steroids</span> against <span class="chemical">cocaine</span> kindled - seizures in mice . 