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: Glial activation and post - synaptic neurotoxicity : the key events in Streptozotocin ( ICV ) induced memory impairment in rats .
### Output Text:
Glial activation and post - synaptic neurotoxicity : the key events in <span class="chemical">Streptozotocin</span> ( ICV ) induced memory impairment in rats . 