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 pressor responses and bradycardia to the alpha 1 - agonist cirazoline ( 0 . 6 and 2 micrograms kg - 1 i . v . ) , the alpha 2 - agonist Abbott - 53693 ( 1 and 3 micrograms kg - 1 i . v . ) , and noradrenaline ( 0 . 1 and 1 . 0 micrograms kg - 1 i . v . ) were determined in conscious SHR with and without chronic prazosin pretreatment .
### Output Text:
The pressor responses and bradycardia to the alpha 1 - agonist <span class="chemical">cirazoline</span> ( 0 . 6 and 2 micrograms kg - 1 i . v . ) , the alpha 2 - agonist <span class="chemical">Abbott - 53693</span> ( 1 and 3 micrograms kg - 1 i . v . ) , and <span class="chemical">noradrenaline</span> ( 0 . 1 and 1 . 0 micrograms kg - 1 i . v . ) were determined in conscious SHR with and without chronic <span class="chemical">prazosin</span> pretreatment . 