Happy Cannabinoid New Year

neurocircuits segment

Every year ends the same way. Journalists look back over the preceding 12 months and make arbitrary lists — the 10 top food stories, the 5 most promising discoveries, and so on. They weigh and assess, and pick the biggest health story of the year, or sum up how pitifully few states of the union have actually shown any improvement in the realm of childhood obesity reduction. Then, the winter holidays happen, and food limitation is a concept nobody wants to think about.

But even so, we decide to clean up our act and make this upcoming year the healthiest one ever. But New Year’s Day falls on a Tuesday, and you’ve found that new programs work better if you start them on a Saturday. So now it’s the 5th, only you think you’re coming down with a cold. So besides the orange juice, you have to indulge in a certain amount of comfort food, no matter how laden with carbohydrates, sugar and fat it may be.

By the time you feel better, it’s the 10th, but this is not the time to start worrying about every little thing you eat. You’ve been sick, and have to rebuild your strength. And next, the thought comes — “You know what? On my birthday, that would be the perfect time to make a new start. The 20th will be the beginning of a whole new life…” And so on, and so forth, until the winter holidays roll around again.

Here we are, several days into the new year, and for a lot of well-intentioned people, it already looks pretty much like the old year. Vows of change usually involve exercise, and people with disposable incomes often fall prey to the fallacy of thinking that if they spend money on it, the job is done. For example, a person might buy a gym membership and then rationalize that paying for the opportunity is somehow the same as actually showing up at the gym every couple of days and working up a sweat.

“Why Good Resolutions About Taking Up a Physical Activity Can Be Hard to Keep” is the eloquently descriptive title of a ScienceDaily piece about a study completed in Bordeaux, France, by two neuroscientists, Francis Chaouloff and François Georges, and a graduate student, Sarah Dubreucq.

Despite the ecstatic testimonials of devoted athletes to how good it makes you feel, most people don’t really enjoy exercise. They suffer from what the researchers describe as “the inability to experience pleasure during physical activity.” Why? What are the neurobiological mechanisms that make people act this way? The team knew from previous research that if the CB1 cannabinoid receptor is missing from a mouse’s brain, it will run on the exercise wheel only about two-thirds as much as a mouse whose CB1 cannabinoid receptors are present.

Why? The article says:

They began by demonstrating that the CB1 receptor controlling running performance is located at the GABAergic nerve endings. They went on to show that the receptor is located in the ventral tegmental area of the brain, which is an area involved in motivational processes relating to reward, whether the reward is natural (food, sex) or associated with the consumption of psychoactive substances.

This is by no means the first time that data has pointed to interactions between the endocannabinoid system, which is the target of delta9-tetrahydrocannabinol (the active ingredient of cannabis), and physical exercise. It was discovered ten years ago that physical exercise activated the endocannabinoid system in trained sportsmen, but its exact role remained a mystery for many years.

The explanation of how they think it works is worth reading for sheer amazement value. They’re talking about a reaction that “inhibits inhibition.” The bottom line is, lacking CB1 receptors leads to reduced performance levels. The report specifies the freshness of these discoveries:

What is original about this research is that it shows that physical exercise can be added to the array of natural rewards regulated by the endocannabinoid system… This work reveals that the endocannabinoid system plays a major role in physical exercise performance through its impact on motivational processes. It thus opens up new avenues of research into the mediators of pleasure — and even addiction — associated with regular physical exercise.

Pictured on this page is a segment from a Medscape chart, and from that page you can click to a large image of the whole chart. Notice how prominently the cannabinoid receptors are listed in the lateral hypothalamus area. The red arrows indicate inhibitory signals the brain gets from the adipose tissue. Messages also come indirectly, via other parts of the hypothalamus. The blue arrows show where stimulatory signals come from — the liver, and indirectly from other parts of the hypothalamus that take their cues from activity in the stomach, intestines, adipose tissue, and muscle. In other words, the pathways are many and subtle.

Your responses and feedback are welcome!

Source: “Why Good Resolutions About Taking Up a Physical Activity Can Be Hard to Keep,” ScienceDaily, 01/04/13
Image by Medscape.com.

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