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: A single MPEP ( 5 mg / kg ip ) injection reduced the basal extracellular dopamine level in the striatum , as well as dopamine release stimulated either by methamphetamine ( 10 mg / kg sc ) or by intrastriatally administered veratridine ( 100 microM ) .
### Output Text:
A single <span class="chemical">MPEP</span> ( 5 mg / kg ip ) injection reduced the basal extracellular <span class="chemical">dopamine</span> level in the striatum , as well as <span class="chemical">dopamine</span> release stimulated either by <span class="chemical">methamphetamine</span> ( 10 mg / kg sc ) or by intrastriatally administered <span class="chemical">veratridine</span> ( 100 microM ) . 