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: The present study examined the influence of excitatory amino acid - mediated mechanisms in the IC on the catalepsy induced by the dopamine receptor blocker haloperidol administered systemically ( 1 or 0 . 5 mg / kg ) in rats .
### Output Text:
The present study examined the influence of excitatory <span class="chemical">amino acid</span> - mediated mechanisms in the IC on the catalepsy induced by the <span class="chemical">dopamine</span> receptor blocker <span class="chemical">haloperidol</span> administered systemically ( 1 or 0 . 5 mg / kg ) in rats . 