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 addition , the disrupted prepulse inhibition induced by d - amphetamine or phencyclidine was restored by 5 - HT6 receptor antagonist in an animal study using rats .
### Output Text:
In addition , the disrupted prepulse inhibition induced by <span class="chemical">d - amphetamine</span> or <span class="chemical">phencyclidine</span> was restored by <span class="chemical">5 - HT6</span> receptor antagonist in an animal study using rats . 