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 magnitude and time course of the increase in heart rate and the decrease in systolic blood pressure after nitroglycerin were similar in the normal and diabetic subjects without autonomic neuropathy , whereas a lesser increase in heart rate and a greater decrease in systolic blood pressure occurred in the diabetic subjects with autonomic neuropathy .
### Output Text:
The magnitude and time course of the increase in heart rate and the decrease in systolic blood pressure after <span class="chemical">nitroglycerin</span> were similar in the normal and diabetic subjects without autonomic neuropathy , whereas a lesser increase in heart rate and a greater decrease in systolic blood pressure occurred in the diabetic subjects with autonomic neuropathy . 