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: Application of a delayed feedback signal , in the form of a 2 - h systemic corticosterone infusion in urethane - anesthetized rats with pharmacological blockade of glucocorticoid synthesis , is without effect on the resting secretion of arginine vasopressin and oxytocin at any corticosterone feedback dose tested .
### Output Text:
Application of a delayed feedback signal , in the form of a 2 - h systemic <span class="chemical">corticosterone</span> infusion in <span class="chemical">urethane</span> - anesthetized rats with pharmacological blockade of glucocorticoid synthesis , is without effect on the resting secretion of <span class="chemical">arginine vasopressin</span> and <span class="chemical">oxytocin</span> at any <span class="chemical">corticosterone</span> feedback dose tested . 