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: GR 55562 ( 0 . 1 - 10 microg / side ) , administered intra - accumbens shell prior to cocaine , dose - dependently attenuated the psychostimulant - induced locomotor hyperactivity .
### Output Text:
<span class="chemical">GR 55562</span> ( 0 . 1 - 10 microg / side ) , administered intra - accumbens shell prior to <span class="chemical">cocaine</span> , dose - dependently attenuated the psychostimulant - induced locomotor hyperactivity . 