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 loss of GAD mRNA - containing neurons in the hilus contrasted with the relative preservation of labeled putative basket cells along the inner margin of the granule cell layer .
### Output Text:
The loss of GAD mRNA - containing neurons in the hilus contrasted with the relative preservation of labeled putative basket cells along the inner margin of the granule cell layer . 