Science Finds Why Exercise Energizes Us

A new study discovered a mechanism in the body that regulates norepinephrine, a hormone central to motivation, stress response and control of blood pressure, pain and appetite. The research has the potential to be used in drugs designed to help fight health problems connected with these functions.

Researchers from the University of Bristol and University College London found that lactate (similar to lactic acid) causes the brain to dump norepinephrine, a hormone fundamental for brain function. Focusing, or even waking up, is almost impossible without the hormone.

Lactate production stems from muscle use, providing further evidence of the connection between exercise and mental health.

Swedish chemist, Carl Wilhelm Schelle, first discovered lactate in spoiled milk back in 1780. Our body produces the neurotransmitter naturally, especially while exercising. In the brain it has always been known as an energy source, deliverable to neurons to keep them firing.

The research, published Tuesday in Nature Communications, finds that lactate also functions as a signal between brain cells. This implies that norepinephrine cells in the brain must have a receptor making them sensitive to lactate.

Professor Sergey Kasparov, from Bristol University's School of Physiology and Pharmacology, said, "Our findings suggest that lactate has more than one incarnation - in addition to its role as an energy source, it is also a signal to neurones to release more noradrenaline."

"The next big task is to identify the receptor which mediates this effect because this will help to design drugs to block or stimulate this response. If we can regulate the release of noradrenaline - which is absolutely fundamental for brain function - then this could have important implications for the treatment of major health problems such as stress, blood pressure, pain and depression," Anja Teschemacher, also from the University of Bristol, added.

"Astrocytes, small non-neuronal star-shaped cells in the brain and spinal cord, are the principle source of brain lactate. The discovery that astrocytes communicate directly with neurones opens up a whole new area of pharmacology which has been little explored," the study's press release concluded.