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: Focal glutamate photostimulation of the granule cell layer at sites distant from the recording pipette resulted in population responses of 1 - 30 s duration in slices from SE survivors but not other groups .
### Output Text:
Focal <span class="chemical">glutamate</span> photostimulation of the granule cell layer at sites distant from the recording pipette resulted in population responses of 1 - 30 s duration in slices from SE survivors but not other groups . 