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: Intraperitoneal administration of cholecystokinin octapeptide sulphate ester ( CCK - 8 - SE ) and nonsulphated cholecystokinin octapeptide ( CCK - 8 - NS ) enhanced the latency of seizures induced by picrotoxin in mice .
### Output Text:
Intraperitoneal administration of <span class="chemical">cholecystokinin octapeptide</span> sulphate ester ( <span class="chemical">CCK - 8</span> - SE ) and nonsulphated <span class="chemical">cholecystokinin octapeptide</span> ( <span class="chemical">CCK - 8</span> - NS ) enhanced the latency of seizures induced by <span class="chemical">picrotoxin</span> in mice . 