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: The other rats showed a strong decrease in the rigidity and the occurrence of stereotyped ( S ) licking and / or gnawing in presence of akinetic or hyperkinetic ( K ) behaviour ( AS / KS group ) , suggesting signs of dopaminergic activation .
### Output Text:
The other rats showed a strong decrease in the rigidity and the occurrence of stereotyped ( S ) licking and / or gnawing in presence of akinetic or hyperkinetic ( K ) behaviour ( AS / KS group ) , suggesting signs of dopaminergic activation . 