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 experiments using specific adrenergic antagonists , we found that pretreatment with the beta - adrenergic receptor antagonist propranolol blocked cocaine - induced anxiety - like behavior in Dbh + / - and wild - type C57BL6 / J mice , while the alpha ( 1 ) antagonist prazosin and the alpha ( 2 ) antagonist yohimbine had no effect .
### Output Text:
In experiments using specific adrenergic antagonists , we found that pretreatment with the beta - adrenergic receptor antagonist <span class="chemical">propranolol</span> blocked <span class="chemical">cocaine</span> - induced anxiety - like behavior in Dbh + / - and wild - type C57BL6 / J mice , while the alpha ( 1 ) antagonist <span class="chemical">prazosin</span> and the alpha ( 2 ) antagonist <span class="chemical">yohimbine</span> had no effect . 