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: Mice subjected to hypotensive episodes showed a significant decrease in latency time ( 178 + / - 156 s ) compared with those injected with saline , NTG + NIMO , or delayed NTG ( 580 + / - 81 s , 557 + / - 67 s , and 493 + / - 146 s , respectively ) .
### Output Text:
Mice subjected to hypotensive episodes showed a significant decrease in latency time ( 178 + / - 156 s ) compared with those injected with saline , <span class="chemical">NTG</span> + <span class="chemical">NIMO</span> , or delayed <span class="chemical">NTG</span> ( 580 + / - 81 s , 557 + / - 67 s , and 493 + / - 146 s , respectively ) . 