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: To achieve this aim , the effects of ouabain injection immediately after and 7 days following a single ICV administration ( at concentrations of 10 ( - 2 ) and 10 ( - 3 ) M ) on locomotion was measured using the open - field test .
### Output Text:
To achieve this aim , the effects of <span class="chemical">ouabain</span> injection immediately after and 7 days following a single ICV administration ( at concentrations of 10 ( - 2 ) and 10 ( - 3 ) M ) on locomotion was measured using the open - field test . 