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: This study was conducted to examine whether prolonged pretreatment with isoproterenol could abolish bromocriptine - induced tachycardia in conscious rats .
### Output Text:
This study was conducted to examine whether prolonged pretreatment with <span class="chemical">isoproterenol</span> could abolish <span class="chemical">bromocriptine</span> - induced tachycardia in conscious rats . 