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: Male Wistar rats were implanted bilaterally with cannulae into the accumbens shell or core , and then were locally injected with GR 55562 ( an antagonist of 5 - HT1B receptors ) or CP 93129 ( an agonist of 5 - HT1B receptors ) .
### Output Text:
Male Wistar rats were implanted bilaterally with cannulae into the accumbens shell or core , and then were locally injected with <span class="chemical">GR 55562</span> ( an antagonist of 5 - HT1B receptors ) or <span class="chemical">CP 93129</span> ( an agonist of 5 - HT1B receptors ) . 