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: In situ hybridization histochemistry , using a digoxigenin - labeled GAD cRNA probe , demonstrated a substantial decrease in the number of GAD mRNA - containing neurons in the hilus of the dentate gyrus in the pilocarpine - treated rats as compared to controls at all time intervals .
### Output Text:
In situ hybridization histochemistry , using a <span class="chemical">digoxigenin</span> - labeled GAD cRNA probe , demonstrated a substantial decrease in the number of GAD mRNA - containing neurons in the hilus of the dentate gyrus in the <span class="chemical">pilocarpine</span> - treated rats as compared to controls at all time intervals . 