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: These results suggest that dehydration and / or the activation of visceral afferent inputs may contribute to the elevation of plasma AVP and the upregulation of AVP gene expression in the PVN and the SON of the Li - induced diabetes insipidus rat .
### Output Text:
These results suggest that dehydration and / or the activation of visceral afferent inputs may contribute to the elevation of plasma <span class="chemical">AVP</span> and the upregulation of <span class="chemical">AVP</span> gene expression in the PVN and the SON of the <span class="chemical">Li</span> - induced diabetes insipidus rat . 