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: RESULTS : Nicotine ( 0 . 05 - 0 . 25 mg / kg ) itself did not produce any significant effect in the EPM test , whereas caffeine ( 70 mg / kg ) and pentylenetetrazole ( 30 mg / kg ) produced an anxiogenic effect , apparent with decreases in open - arm time and entry .
### Output Text:
RESULTS : <span class="chemical">Nicotine</span> ( 0 . 05 - 0 . 25 mg / kg ) itself did not produce any significant effect in the EPM test , whereas <span class="chemical">caffeine</span> ( 70 mg / kg ) and <span class="chemical">pentylenetetrazole</span> ( 30 mg / kg ) produced an anxiogenic effect , apparent with decreases in open - arm time and entry . 