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 investigated the effect of repeated treatment with fluvoxamine , a selective serotonin uptake inhibitor , on behavioral effects of dopaminomimetics and methoxamine and on the animal behavior in the " behavioral despair " test .
### Output Text:
We investigated the effect of repeated treatment with <span class="chemical">fluvoxamine</span> , a selective <span class="chemical">serotonin</span> uptake inhibitor , on behavioral effects of dopaminomimetics and <span class="chemical">methoxamine</span> and on the animal behavior in the " behavioral despair " test . 