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: By implantation of electrodes and electrophysiological recording in vivo , the results showed that Rg1 restored the long - term potentiation ( LTP ) impaired by morphine in both freely moving and anaesthetised rats .
### Output Text:
By implantation of electrodes and electrophysiological recording in vivo , the results showed that <span class="chemical">Rg1</span> restored the long - term potentiation ( LTP ) impaired by <span class="chemical">morphine</span> in both freely moving and anaesthetised rats . 