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: The goal of this study was to assess the interactive effects of chronic anabolic androgenic steroid ( AAS ) exposure and brain serotonin ( 5 - hydroxytryptamine , 5 - HT ) depletion on behavior of pubertal male rats .
### Output Text:
The goal of this study was to assess the interactive effects of chronic anabolic androgenic <span class="chemical">steroid</span> ( AAS ) exposure and brain <span class="chemical">serotonin</span> ( <span class="chemical">5 - hydroxytryptamine</span> , <span class="chemical">5 - HT</span> ) depletion on behavior of pubertal male rats . 