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: Naloxone ( 2 . 5 mg / kg , i . v . ) reversed respiratory paralysis , glutamate and GABA levels to control values in brain stem and cortex with no changes in caudate or cerebellum .
### Output Text:
<span class="chemical">Naloxone</span> ( 2 . 5 mg / kg , i . v . ) reversed respiratory paralysis , <span class="chemical">glutamate</span> and <span class="chemical">GABA</span> levels to control values in brain stem and cortex with no changes in caudate or cerebellum . 