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 a separate group of mice not subjected to behavioral studies , the same dose of NTG ( n = 3 ) and NTG + NIMO ( n = 3 ) caused mean arterial blood pressure to decrease from 85 . 9 + / - 3 . 8 mm Hg sem to 31 . 6 + / - 0 . 8 mm Hg sem and from 86 . 2 + / - 3 . 7 mm Hg sem to 32 . 6 + / - 0 . 2 mm Hg sem , respectively .
### Output Text:
In a separate group of mice not subjected to behavioral studies , the same dose of <span class="chemical">NTG</span> ( n = 3 ) and <span class="chemical">NTG</span> + <span class="chemical">NIMO</span> ( n = 3 ) caused mean arterial blood pressure to decrease from 85 . 9 + / - 3 . 8 mm Hg sem to 31 . 6 + / - 0 . 8 mm Hg sem and from 86 . 2 + / - 3 . 7 mm Hg sem to 32 . 6 + / - 0 . 2 mm Hg sem , respectively . 