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: These results indicate that noradrenergic neurons have an important role in the manifestation of catalepsy induced by THC , whereas dopaminergic neurons are important in catalepsy induced by haloperidol .
### Output Text:
These results indicate that noradrenergic neurons have an important role in the manifestation of catalepsy induced by <span class="chemical">THC</span> , whereas dopaminergic neurons are important in catalepsy induced by <span class="chemical">haloperidol</span> . 