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: Maximal contraction to norepinephrine was modestly reduced in arteries from LNNA compared with control rats whereas the maximum contraction to ET - 1 was significantly reduced ( 54 % control ) .
### Output Text:
Maximal contraction to <span class="chemical">norepinephrine</span> was modestly reduced in arteries from <span class="chemical">LNNA</span> compared with control rats whereas the maximum contraction to ET - 1 was significantly reduced ( 54 % control ) . 