Why Are Our Bodies Awash With Endocannabinoids?

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Key Points

• Endocannabinoids, marijuana-like chemicals called AEA and 2-AG, modulate the brain’s reward circuitry.
• These chemicals influence the degree of pleasure you experience.
• The entire body is awash in these chemicals and they influence your experiences.

It is widely recognized today that two endocannabinoid chemicals, called AEA and 2-AG, modulate the brain’s reward circuitry. They achieve this effect by indirectly influencing the release of dopamine in the brain’s reward centers. Through these interactions, the endocannabinoids influence the degree of pleasure that you experience. Scientists have speculated that the release of these chemicals in the brain underlies the pleasure we feel when socializing with friends. A recent study has discovered that endocannabinoids that are not inside the brain also influence the pleasure of social interactions. Apparently, the entire body is awash in these marijuana-like chemicals and their moment-to-moment fluctuations in blood and brain significantly influence the experience of daily pleasures.

Endocannabinoids in the Blood May Influence How We Feel
Endocannabinoids are also present in the serum and plasma. Lots of different tissues in the body, including fat cells, endothelial cells, immune cells, and some visceral organs, release endocannabinoids into the blood. Why would these bodily tissues release endocannabinoids? AEA, for example, controls a series of critical biological functions such as cell proliferation, survival, or programmed cell death. Some of these endocannabinoids in the blood might have also originated in the brain and then easily exited through the blood-brain barrier. Although this is possible, the very short half-lives of endocannabinoids suggest that a large contribution from the brain is unlikely. Fluctuations in the levels of endocannabinoids in the blood are thought to influence how we feel. The levels of these endocannabinoids fluctuate throughout the day and correlate with our mood.

One study reported that women with major depression showed that the concentrations of AEA in the blood were inversely correlated with their level of anxiety. This discovery suggests that fluctuations in the release of peripheral AEA may influence the degree of anxiety in humans with affective disorders. When a similar study was performed on healthy, non-depressed, volunteers, basal serum levels of AEA were again inversely correlated with subjective ratings of anxiety. Anxiety is not the only mood that these molecules influence; your subjective ratings of sexual arousal are significantly related to the level of 2-AG in your blood.

Your Brain Is Informed About Fluctuations in the Blood Levels of AEA
What is happening here? Is your brain truly influenced by endocannabinoids that are released into the blood from your fat cells, kidneys, and other tissues? A recent study investigated the effects of peripheral endocannabinoids, those floating around in our blood, on brain function when we experience something pleasurable. This MRI study of young healthy human subjects discovered that basal concentrations of AEA, but not 2-AG, were positively correlated with increased activity in reward-associated brain centers in response to reward. Essentially, your brain is somehow informed about fluctuations in the blood levels of AEA and responds to rewards accordingly. The scientists speculated that the endocannabinoids in the blood were either indirectly acting upon the brain or actively crossing the blood-brain barrier.

This study also discovered that blood levels of AEA were inversely correlated with a personality measure called “reward dependence.” Why is this important? Reward dependence characterizes the individual’s dependency on signals of mainly social reward, in particular verbal signals of social approval and social support. This finding suggests that endocannabinoids in the blood that originate throughout your body significantly influence the pleasure you experience when socializing with others.