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: Moreover , PREGS is able to reverse the amnesic - like effects of NMDAR and GABA ( A ) R ligands .
### Output Text:
Moreover , <span class="chemical">PREGS</span> is able to reverse the amnesic - like effects of NMDAR and <span class="chemical">GABA</span> ( A ) R ligands . 