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: Plasma concentration of AVP and transcripts of AVP gene in the PVN and SON were significantly increased in the Li - treated rats compared with controls .
### Output Text:
Plasma concentration of <span class="chemical">AVP</span> and transcripts of <span class="chemical">AVP</span> gene in the PVN and SON were significantly increased in the <span class="chemical">Li</span> - treated rats compared with controls . 