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 relationship between hippocampal acetylcholine release and cholinergic convulsant sensitivity in withdrawal seizure - prone and withdrawal seizure - resistant selected mouse lines .
### Output Text:
The relationship between hippocampal <span class="chemical">acetylcholine</span> release and cholinergic convulsant sensitivity in withdrawal seizure - prone and withdrawal seizure - resistant selected mouse lines . 