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: ( R ) - alpha - methylhistamine ( RAMH ) ( 5 microg i . c . v . ) and thioperamide ( THP ) ( 15 mg / kg i . p . ) , per se did not cause catalepsy .
### Output Text:
<span class="chemical">( R ) - alpha - methylhistamine</span> ( <span class="chemical">RAMH</span> ) ( 5 microg i . c . v . ) and <span class="chemical">thioperamide</span> ( <span class="chemical">THP</span> ) ( 15 mg / kg i . p . ) , per se did not cause catalepsy . 