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: Centrally mediated cardiovascular effects of intracisternal application of carbachol in anesthetized rats .
### Output Text:
Centrally mediated cardiovascular effects of intracisternal application of <span class="chemical">carbachol</span> in anesthetized rats . 