In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

Q: Effect of nicotine pretreatment on arsenic-induced oxidative stress in male Wistar rats.

A: nicotine
****
Q: Phenformin has a direct inhibitory effect on the ATP-sensitive potassium channel.

A: potassium
****
Q: Estradiol replacement enhances cocaine-stimulated locomotion in female C57BL/6 mice through estrogen receptor alpha.

A:
estrogen
****