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: A significant decrease in neuronal density of the hippocampal hilar formation was identified in vehicle - and PDTC - treated rats following status epilepticus .
### Output Text:
A significant decrease in neuronal density of the hippocampal hilar formation was identified in vehicle - and <span class="chemical">PDTC</span> - treated rats following status epilepticus . 