Noradrenaline molecule. Computer artwork of a molecule of the neurotransmitter and hormone noradrenaline, or norepinephrine (C8.H11.N.O3). The atoms (spheres) are colour-coded: carbon (black), oxygen (red), nitrogen (blue) and hydrogen (white). Noradrenaline is a substance that transmits messages in the nervous system. It has effects on the heart, blood vessels, intestines, liver and bladder. It is also used as an emergency drug to restore dangerously low blood pressure, when it is injected into a vein or directly into the heart.