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 glutamatergic N - methyl - D - aspartate ( NMDA ) receptor has been implicated in the pathophysiology of schizophrenia .
### Output Text:
The glutamatergic <span class="chemical">N - methyl - D - aspartate</span> ( <span class="chemical">NMDA</span> ) receptor has been implicated in the pathophysiology of schizophrenia . 