Your brain on exercise: rewarded with dopamine by cannabinoid receptors.

Lack of enough physical activity is a huge problem in the obesity-plagued modern world. With much of physical activity removed from work and daily life, to be fit and not obese, we have to exercise for extended periods of time, in activities like jogging, fast walking, bike riding and other aerobic exercise. Our willingness to exercise in this way is really a cornerstone of our health, and our society’s health. Probably more than anything single factor, our health care system would benefit from people getting more exercise. New research now reports the crucial role of cannabinoid receptors and our endocannabinoid regulatory system in our motivation to keep moving.

Research out of France, reported in Biological Psychiatry shows how small protein cannabinoid receptors operating in the walls of nerve cells in the  brain reward exercise. This unlocks a key to voluntary exercise, and perhaps ways to promote it.  Also reported in ScienceDaily, the research reported that the endocannabinoid system, especially CB1 receptors in certain parts of the brain, reward our bodies and minds with pleasurable sensations. This research was with mice, not humans, but the physiology and responses are very similar. Lack (or blockage) of these receptors caused a sharp drop in the amount of exercise control mice were willing to do.

For us to continue to exercise, rather than stopping, depends a lot on how we feel. If tired and uncomfortable we might well stop; if exhilarated and “in the zone,” we continue. How we feel during exercise, it turns out, depends much on how much of the feel-good substance, dopamine, our brains produce and receive.  Our dopamine levels, this research shows, are controlled in part by our endocannabinoid systems and CB1 receptors in certain parts of the brain. CB1 receptors are activated by our natural endocannabinoids such as anandamide. They also fit like lock and key and are activated by plant cannabinoids, especially THC, from cannabis.

Dopamine is an organic chemical produced in several areas of the brain. Many brain functions involve dopamine, especially learning, voluntary movement, reward and motivation. We feel higher dopamine levels as enjoyment and are rewarded by the experience, making us want to continue or repeat. Drugs like cocaine increase and prolong dopamine levels. The Bordeaux, France researchers studied dopamine producing nerve cells in the brain’s ventral tegmental area (VTA) known to play an important role in motivation. By working with mice with CB1 receptors present or absent or blocked, they found marked difference in how much running wheel time the rodents would spend.

The researchers had previously found “that the endogenous stimulation of cannabinoid type-1 (CB1) receptors is a prerequisite for voluntary running in mice,” but did not understand the mechanisms. In experiments involving “in vivo electrophysiology, the consequences of wheel running on VTA dopamine (DA) neuronal activity” on mice with combinations of CB1 blockage and GABA blockage. GABA is an inhibitory neurotransmitter that reduces levels of dopamine produced by other neurons. Cannabinoid receptor activation in GABA neurons inhibits this inhibitory effect on dopamine. This “inhibition of inhibition” results in an increased level of dopamine produced in this motivation area of the brain.

Exercise promotes endocannabinoid activation of CB1 receptors and this activation encourages continued exercise. If we exercise enough to allow them, our bodies reward us for the physical activities that are so good for us.

Not mentioned in this research, the “runner’s high” is likely a function of endocannabinoids, along with the endorphins. For earlier evidence of the runner’s high association with the endocannabinoid system check Runner’s high – your body rewarding exercise.

Bliss out (and pump up) your brain with exercise.

Just as doing push-ups pumps up the size of your triceps, so does aerobic exercise appear to increase the volume of your brain! American researchers reporting in the British Journal of Sports Medicine show that physical exercise, especially aerobic activity, improves the functioning and structure of the brains of older people.

Improvements in brain size, with increased volumes of grey and white matter, and better brain function were found in both those with and without dementia. The so called functions of “executive control,” that help us carry on our lives planning, remembering and changing tasks are those first attacked by dementia. But study co-author Art Kramer of the University of Illinois notes that these functions are those most helped with exercise. Dementia is not only forestalled, but in some ways actually reversed with 6 months of aerobic activity. Brains benefiting from the exercise exertions of their owners maintained plasticity, essentially the capabilities to continue growing, developing and learning.

Although huge rewards accrue to both brain and body from simply walking, these researchers point out the increased benefit from more rigorous aerobic activities, such as jogging, that cause increases in heart rate and rate of breathing. So by all means walk your 10,000 steps a day, at least 5 miles, but also pick up the pace for some of those steps.  Jogging one of those five miles and moving your heart rate up into your age-appropriate training zone will yield great benefits, toning your body and growing your brain. Professor Kramer summarized, “We can safely argue that an active lifestyle with moderate amounts of aerobic activity will likely improve cognitive and brain function, and reverse the neural decay frequently observed in older adults.”

If you bliss out your brain with exercise, there is now good evidence your brain will return the favor. “Runner’s high,” is a flowing, blissful, pain-free experience associated with aerobic exercise. Formerly, the enjoyable mental and physical state was associated solely with endorphins, the body’s natural opiates. With the discovery of the endocannabinoid receptor system and endogenous cannabinoids produced by our own bodies, such as anandamide and 2-AG, this explanation is taking a new turn. After you begin exercising, your level of natural bliss cannabinoid anandamide elevates, and more of these bliss molecules float in your bloodstream, ready to jump the blood-brain barrier and activate CB1receptors on your nerve cells. The result is pain reduction and mood elevation.  So, in addition to endorphins, endocannabinoids such as anandamide reward you for your exercise efforts.

Better adaptive functioning and increased brain volumes are, at least in part, due to neurogenesis, the birth of new brain cells. Both exercise and cannabinoids promote neurogenesis. So, to gain huge health rewards, second-by-second, year-by-year, for your entire life, bliss out your brain with exercise. Walk every day, run some too, lift some weights, and every cell in your brain and body benefits.