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Why Do We Have Cannabinoid Receptors?

There's no doubt about it—cannabis is a mind-altering plant. But, why? Here's what causes the psychoactive and therapeutic effects of cannabis.
October 24, 2019
Written by Anna Wilcox, medically reviewed by Dr. Michael Verbora MBA, MD
What are cannabinoid receptors?

Photo by Zachary Tan on Unsplash

Have you ever wondered why the cannabis plant can produce such strong physical and mental effects?  As it turns out, the herb interacts with the human body in ways that no other plant can. 

Cannabis contains chemical compounds called cannabinoids, which are unique to the plant alone. These cannabinoids are able to engage with special landing locations on human cells called cannabinoid receptors. But, why do we have these cannabinoid receptors, anyway? Were we made to consume cannabis? 

Well, not exactly.

What Are Cannabinoid Receptors?

Cells detect signals from their surroundings through specialized sites called cell receptors. Cell receptors sit on the surface of cells and can be activated or blocked by incoming chemical messengers. 

There are many different types of cell receptors, and each of them responds to specific classes of chemical compounds—just like a lock only opens with the right key. 

Cannabinoid receptors are a class of specialized cell receptors that respond to chemicals called cannabinoids. Through cannabinoid receptors, cells can receive cannabinoid messages from their neighbors and their surroundings. 

Cannabinoids can come from both external and internal sources; exogenous cannabinoids come from sources like the cannabis plant. Endogenous cannabinoids, on the other hand, are produced naturally by the human body. 

Cannabinoids and cannabinoid receptors are a part of a more extensive endocannabinoid system (ECS). The ECS is a system that consists of cannabinoid messengers, cannabinoid receptors, and enzyme proteins. Together, these entities work to maintain homeostasis in the human body. Homeostasis is the scientific term for optimum balance or equilibrium. 

When cannabinoids engage with a cannabinoid receptor, they affect the natural equilibrium inside of the cell. In turn, the resulting change may have a cascading effect on the body’s internal harmony. 

For this reason, changes to the endocannabinoid system can have wide-ranging effects on human and animal health. These changes are true whether they come from consuming cannabis or from experiencing a pleasant or stressful event.

Why Do We Have Cannabinoid Receptors?

What do cannabinoid receptors do?

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Cannabinoid receptors are a part of an innate stress-management and learning system. In short, we have cannabinoid receptors to help us tolerate stress and to help us learn and respond to our environment. 

After a stressful event, whether a physical injury or an emotional shock, the endocannabinoid system works to bring the body back into a harmonious state. 

Endogenous cannabinoids, for example, are released in response to physical pain. After injury, cannabinoid receptors may increase in concentration. In terms of emotional stress, the endocannabinoid system may help us forget negative or traumatic memories

Without cannabinoid receptors, we might experience symptoms like chronic pain, chronic inflammation, seizure, lack of appetite, and difficulty regulating our mood. 

Where Are CB1 And CB2 Receptors Located?

There are two main types of cannabinoid receptors: cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). But, scientists heavily speculate that three or more cannabinoid receptors may exist, we just haven’t found them yet. 

The location of cannabinoid receptors says a lot about what they do. CB1 receptors, for example, are most abundant in the brain. CB2 receptors, on the other hand, are most abundant throughout the body. It’s not surprising, then, that both of these receptors have different functions. Here’s some more detail:

where are cannabinoid receptors located?

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Where Are CB1 Receptors Found?

The CB1 receptor is predominant throughout the nervous system, although the receptors are in other organs and other tissues as well, just in lower concentrations. 

In the central nervous system, the CB1 receptor is highly dense throughout brain tissue. But, the CB1 receptor is not evenly dispersed throughout the organ. Instead, it is particularly abundant in certain brain regions, like those responsible for:

  • cognition
  • movement
  • memory
  • emotion

For these reasons, the intoxicating effects of THC come as no surprise— look at where the receptors are located! The psychoactive molecule often causes slow movements, a skewed sense of time, and forgetfulness. Now, we can understand why.

Where Are CB2 Receptors Found?

CB2 receptors are located primarily in immune organs and on immune cells. Although, like CB1 receptors, CB2 is also in the brain. Unlike CB1 receptors, CB2 receptors are not associated with intoxication. Instead, these receptors help mediate responses to infection and injury. 

Cannabinoid Receptors In The Brainstem

There is a reason why it’s seemingly impossible to overdose on cannabis fatally: cannabinoid receptors are not found in the brainstem.

The brainstem is home to several vital reflex centers, which control your heartbeat and automatic breathing. 

Without cannabinoid receptors, cannabis compounds cannot affect these areas. As such, consuming cannabis will not stop your heartbeat or cause you to stop breathing. Other substances, like opioid pain medications and alcohol, can affect these reflex centers. So, it’s easier to overdose on these substances fatally.

What Do Cannabinoid Receptors Do?

cannabinoid receptor function

Photo by Toa Heftiba on Unsplash

What cannabinoid receptors do depends on where they’re located. In the brain, for example, cannabinoid receptors influence the tone of excitatory and inhibitory neurotransmitters. A neurotransmitter is a chemical messenger specific to nerve cells, like those found in the brain.  Excitatory neurotransmitters are stimulating, while inhibitory neurotransmitters are calming.

In the brain, cannabinoids act as a balancing mechanism for excitability and depression. This balancing is one way that the brain maintains homeostasis. After all, if a car is running too hot, it’s time to turn it off. 

Since cannabinoid receptors are found throughout the brain and body, they can influence a wide variety of bodily functions. These include,

  • Appetite
  • Growth and development
  • Inflammatory response
  • Learning
  • Memory
  • Metabolism
  • Mood
  • Movement
  • Pain sensation
  • Reproduction

It’s important to note, however, that this is not a comprehensive list of what cannabinoid receptors do. These receptors not only play different roles depending on where they’re located, but the role of the endocannabinoid system also changes throughout your life cycle. 

Cannabinoids, for example, may influence the growth and development of a fetus. After birth, cannabinoids are passed through breast milk to encourage a baby to suckle. Throughout childhood and old age, cannabinoids may influence learning and plasticity in the brain.

In old age, cannabinoid messengers may protect the brain from degeneration.

October 24, 2019 — Last Updated October 31, 2019
Written by Anna Wilcox
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