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: Trazodone at 30 , 40 and 50 mg / kg i . p . induced catalepsy and antagonized apomorphine and dexamphetamine stereotypies .
### Output Text:
<span class="chemical">Trazodone</span> at 30 , 40 and 50 mg / kg i . p . induced catalepsy and antagonized <span class="chemical">apomorphine</span> and <span class="chemical">dexamphetamine</span> stereotypies . 