TASK DEFINITION: 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.
PROBLEM: COX-1 and COX-2 inhibition in horse blood by phenylbutazone, flunixin, carprofen and meloxicam: an in vitro analysis.

SOLUTION: carprofen

PROBLEM: Use of the norepinephrine transporter as a reporter gene for non-invasive imaging of genetically modified cells.

SOLUTION: norepinephrine

PROBLEM: Nicotine-induced contraction in the rat coronary artery: possible involvement of the endothelium, reactive oxygen species and COX-1 metabolites.

SOLUTION:
oxygen