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: Therefore , the effects of carteolol , a beta - adrenoceptor antagonist , on haloperidol - induced catalepsy in rats were behaviorally studied and compared with those of propranolol and biperiden , a muscarinic receptor antagonist .
### Output Text:
Therefore , the effects of <span class="chemical">carteolol</span> , a beta - adrenoceptor antagonist , on <span class="chemical">haloperidol</span> - induced catalepsy in rats were behaviorally studied and compared with those of <span class="chemical">propranolol</span> and <span class="chemical">biperiden</span> , a muscarinic receptor antagonist . 