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: We observed no changes in nicotine - induced locomotor response , striatal L - [ 3H ] nicotine and [ 3H ] spiperone binding in the animals pretreated with nicotine for 1 day .
### Output Text:
We observed no changes in <span class="chemical">nicotine</span> - induced locomotor response , striatal L - [ 3H ] <span class="chemical">nicotine</span> and [ 3H ] <span class="chemical">spiperone</span> binding in the animals pretreated with <span class="chemical">nicotine</span> for 1 day . 