Adrenaline hormone molecule. Computer artwork showing the molecular structure of adrenaline (epinephrine). Adrenaline is a hormone and neurotransmitter produced in the adrenal glands. It regulates heart rate, blood vessel and air passage diameters, and metabolic shifts. Adrenaline is released in times of stress and is an important part of the fight or flight response. It is used as a drug to treat severe asthma and anaphylactic shock. Atoms are represented as spheres and are colour-coded: carbon (black), hydrogen (white), nitrogen (blue), oxygen (red).