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: In vivo microdialysis demonstrated that an intraperitoneal administration of pilocarpine induced a pronounced increment of hippocampal glutamate and aspartate whereas no significant change was observed on the level of glycine and GABA .
### Output Text:
In vivo microdialysis demonstrated that an intraperitoneal administration of <span class="chemical">pilocarpine</span> induced a pronounced increment of hippocampal <span class="chemical">glutamate</span> and <span class="chemical">aspartate</span> whereas no significant change was observed on the level of <span class="chemical">glycine</span> and <span class="chemical">GABA</span> . 