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: Immunohistochemical studies showed that administration of terbutaline on PN 2 to 5 produced a robust increase in microglial activation on PN 30 in the cerebral cortex , as well as in cerebellar and cerebrocortical white matter .
### Output Text:
Immunohistochemical studies showed that administration of <span class="chemical">terbutaline</span> on PN 2 to 5 produced a robust increase in microglial activation on PN 30 in the cerebral cortex , as well as in cerebellar and cerebrocortical white matter . 