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: Pre - treatment of the CCK2 receptor antagonist L - 365 , 260 ( 10ug , i . c . v ) reversed the effects of CCK - 8 , but the CCK1 receptor antagonist L - 364 , 718 ( 10ug , i . c . v ) did not .
### Output Text:
Pre - treatment of the CCK2 receptor antagonist L - 365 , 260 ( 10ug , i . c . v ) reversed the effects of <span class="chemical">CCK - 8</span> , but the CCK1 receptor antagonist L - 364 , 718 ( 10ug , i . c . v ) did not . 