The Endocannabinoid System

Thanks to the cannabis plant, scientists managed to decipher the primordial language that our cells use to communicate. From the womb to the coffin, for countless generations, the Endocannabinoid System guides and protects organisms. However, a strong gap existed between the world of science and the general public during the 1990s. Except for a few reps in the scientific community, few people knew about the Endocannabinoid System. Doctors, journalists, public representatives ... hardly anyone was updated on the latest evidence of scientific research that went as far as to discover and explain why Cannabis is such a versatile remedy, and why it is, by far, the most popular illicit substance in the world.   

The Endocannabinoid System: its history and discoveries

From the plant to the human body: how and when the Endocannabinoid System was discovered

Using a plant that has been around for thousands of years, we have discovered a new physiological system of immense importance.

Raphael Mechoulam says, believed to be the father of the international community on cannabinoid research. "We wouldn't have been able to get there if we hadn't looked at the plant."

In the two decades that followed the identification and synthesis of THC, the psychoactive molecule of Cannabis, by scientists Mechoulam and colleague Yoel Gaoni in Israel in 1964, scientists have learned a great deal about the pharmacology, biochemistry and clinical effects of Cannabis. But nobody yet really knew how this plant worked, what it really did (at a molecular level) on the brain to alter consciousness, stimulate appetite, decrease nausea, quell seizures (epileptic), and relieve pain. Nobody understood why smoking marijuana could block muscle spasms in multiple sclerosis patients in seconds; nobody knew why it improved the mood.

When American researchers at John Hopkins University in 1973 identified receptor sites capable of binding to opioids (substances such as morphine and heroin) in the brain, some scientists expected that the discovery of cannabis receptor sites would follow shortly thereafter. Yet 15 years passed before a study funded by the United States government at the School of Medicine of St. Louis University determined that the mammalian brain has receptor sites, or specialized proteins, which, incorporated in cell membranes, respond pharmacologically to the molecules present in the resin of cannabis. 

How and when the cannabinoid receptor discovery occurred

A powerful molecule analogous to THC and synthesized by Pfizer (the CP55,940) allowed researchers to begin mapping the precise positions of cannabinoid receptors in the brain, following the signals emanating from a radioactive tag "linked" to this molecule. It will not be surprising to find that the regions of maximum receptor concentration have been identified in the hippocampus (memory), cerebral cortex (cognition), cerebellum (motor coordination), basal ganglia (movement), hypothalamus (appetite) and amygdala (emotions) and gray matter periaqueductal (pain), i.e. the main effects of cannabis on the brain.

Cannabinoid receptors are not present in the areas of the brain that control cardiovascular and respiratory functions, which coincides with the lack of lethality of an overdose of THC (unlike, for example, high doses of opioids).

On July 18, 1990 at a conference of the Institute of Medicine of the National Academy of Science, Dr. Lisa Matsuda announced that she and her colleagues from the NIMH (National Institute of Mental Health) had reached a fundamental discovery, locating the precise sequence of the DNA encoding THC-sensitive receptors in a mouse brain.

Dr. Matsuda also disclosed that she had successfully cloned the cannabis sensitive receptor, and that she had named it with the acronym CB1. People have the same receptor, which consists of a string of 472 amino acids strung like pearls in a chain that sways in and out of the cell membrane seven times.

CB1 and CB2 receptors.

Cannabinoid receptors function as tools for coding changes, small scanners perpetually prepared to collect biochemical signals that flow around the cell.

These electrifying innovations opened the doors to the "decade of the brain", as defined during the meeting of the National Academy of Science.

During the 1990s, in fact, there was more progress in neuroscience than in all the years previously combined.

How and when did the discovery of endocannabinoids occur

Just as studies on opium resulted in the discovery of endorphins, (the natural morphine-like of our brains), equally, research on Cannabis would have led to the discovery of a natural substance, produced by our bodies, similar to THC: our "Internal cannabis", so to speak.

In 1992, a collaboration between researchers William Devane, Lumir Hanus, Roger Pertwee and Raphael Mechoulam brought to light a new neurotransmitter, therefore called an "endogenous cannabinoid" or, in short, "endocannabinoid", a molecule that binds to the same brain receptors that are sensitive to THC.

The researchers called this substance "Anandamide", (abbreviated as AEA), deriving the word from Ananda, the Sanskrit for "happiness", "bliss". (5)

In 1995, the Mechoulam group discovered, in parallel with another group of Japanese researchers, a second important endocannabinoid, 2-arachidonylglycerol, abbreviated with the acronym "2-AG". This new endocannabinoid binds not only to receptors present mainly in the brain, but also to a second type, called CB2 receptors.

When is the Endocannabinoid System recognized by the international scientific community?

Endocannabinoids and their receptors emerged as "hot topics" among scientists who shared their findings in hyper-specialized journals and at annual symposia hosted by the International Cannabinoid Research Society (ICRS).

Since 1990, annual meetings of specialized scientists began studying the Endocannabinoid System, which were later formalized as a scientific research company since 1992 under the name of ICRS.

The company, born in the United States from about fifty delegates (there are now more than 500 from all over the world), was originally supported by research funds from the American government.

The exchanges within ICRS began to draw the attention of the big pharmaceutical companies, which were paying attention to the latest discoveries on cannabinoid science, while still few people outside the scientific community were aware of it.

Progress in this nascent expanding field would pave the way for new therapy strategies for various pathologies, including cancer, diabetes, neuropathic pain, arthritis, osteoporosis, obesity, Alzheimer's, Multiple Sclerosis, depression and many other diseases that seemed beyond the scope of conventional treatments.

The 1990s: the new scientific era for cannabis

Cloning the cannabinoid receptor in 1990 was crucial for this to happen. Since that extraordinary discovery, the doors were opened to scientists to test receptors with various substances, testing them as keys in a lock.

Some keys, called "agonist" molecules in pharmacology, managed to open the padlock; others, the "antagonists", to block it.


The researchers also developed genetically modified mice, called knockouts, that lack the cannabinoid receptor. When THC was administered to a knockout mouse, this molecule had no effect, as THC had no padlock to attach to, and therefore could not trigger any activity.

This was further evidence that THC worked by activating cannabinoid receptors in the central nervous system. 

Finally, after 50 centuries of medicinal use, the scientific basis for therapeutic cannabis was starting to emerge. 

Endocannabinoid system: what it is and what its functions are

Was the cannabis plant or the endocannabinoid system born first?

By tracing the molecular pathways of THC, scientists accidentally discovered a unique and hitherto unknown molecular signage that is involved in the regulation of a wide range of biological functions.

Scientists call it the "Endocannabinoid System" (abbreviated to ECS from English), from the plant that led to its identification. The name may suggest that the plant came first, but in reality, as explained by Dr. John McPartland, physician and phytochemist and cannabis researcher from the early 1980s:


By comparing the genetics of cannabinoid receptors in different species, we estimate that the Endocannabinoid System evolved into primitive animals over 600 million years ago. This ancient internal signage existed long before Cannabis appeared on Earth, when the most complex forms of life were sponges.

Dr. John McPartland


Why does the Endocannabinoid System exist?

The Endocannabinoid System is present in fish, reptiles, worms, leeches, amphibians, birds and mammals - in all animals except insects.

Given its long evolutionary history, scientists have deduced that the Endocannabinoid System should serve for functions of fundamental importance to animal physiology.

From sea urchins, to small nematodes, and all vertebrate species share the Endocannabinoid System as an essential part of life and adaptation to environmental changes.

Mauro Maccarrone, biochemist and UCBM professor in Rome shows the Mechoulam Award 2016, the ICRS annual award

The discovery of the Endocannabinoid System brings extraordinary implications for almost every area of ​​medical science, including reproductive biology. Dr. Mauro Maccarone, professor of biochemistry and one of the leading experts in the field, describes the Endocannabinoid System as "the guardian angel" of reproduction.

Endocannabinoid signage proves decisive throughout the reproductive process, and, in mammals, from spermatogenesis to fertilization, transportation of the zygote to the oviduct, nesting of the embryo in the womb, fetal development, and even the development of the baby once born.

The receptors of this system proliferate in the placenta and facilitate the so-called "cross-talk", that is, the blow and response that exists between the embryo and the mother.

It is for this reason that the Endocannabinoid System exists in so many different species and has survived millennia of evolution: a jam in the system could result in serious problems, including (in women) an ectopic pregnancy and abortions.

Israeli neuroscientist Ester Fride showed that so-called "knockout" mice, that is, with the Endocannabinoid System blocked, resemble children who suffer from staturo-ponderal growth retardation. Without Cannabinoid receptors, mice lose vitality and die prematurely.

We know that the levels of endocannabinoids in breast milk have a critical importance for the initiation of feeding in infants and the interaction between the endocannabinoids present in milk and the receptors present on the tongue, allows to maintain balanced appetite and assimilation of food, ensuring the child survival. 

Endocannabinoids are the substances that our bodies naturally create to stimulate the receptors of the Endocannabinoid System and life itself would not be possible for those of us who do not have cannabinoid receptors.

What functions does the Endocannabinoid System perform?

In each tissue, the Endocannabinoid System performs different tasks, but the goal is always the same: homeostasis, or bio-balance, that is the maintenance of a stable internal environment, despite the oscillations of the external environment.

Cannabinoids promote homeostasis at all levels of biological life, from subcellular to organs and organism and, probably, to the interaction between organisms.

Here is an example: autophagy, a process in which a cell seizes part of its content to be self-digested and recycled, is mediated by the Endocannabinoid System.

This process keeps normal cells alive, allowing them to maintain a balance between synthesis, decomposition, and subsequent recycling in cellular products; on the other hand, however, it has a deadly effect on malignant tumor cells, causing them to have programmed cell suicide.

Of course, the death of cancer cells promotes homeostasis and survival throughout the body.

Professor Vincenzo Di Marzo, one of the most influential pharmacologists in the world, has been conducting research on the Endocannabinoid System since the late 1980s, publishing hundreds of pioneering discoveries; he, together with colleagues Tiziana Bisogno and Luciano DePetrocellis, summarized the functions of the Endocannabinoid System such as:


A central regulator capable of modulating and balancing the main activities of organisms such as eating, sleeping, relaxing, protecting and forgetting. 

Vincenzo Di Marzo, Tiziana Bisogno and Luciano DePetrocellis

Although these observations have now been integrated for twenty years of scientific research, the description of Italian researchers from '98 remains an excellent simplification of the main functions of the ECS.

How the Endocannabinoid System protects the Nervous System

Before the discovery of the Endocannabinoid System it was known that the signs called in neurobiology "antegrade" (or from the Greek, antodromic, which we will illustrate in "How does a cannabinoid receptor work?") Occurred only during the developmental stages of the embryonic brain. Discovering and studying the Endocannabinoid System has overturned this concept, as it has been shown that it also uses this signaling method in the brain of adults.

We know that endocannabinoids choreograph "a wide range of processes in the development of the embryonic brain", thanks to the definition of MacPartland, including the proliferation of stem cells and their differentiation, a process guided by extracellular signals transmitted to cannabinoid receptors. 

Since the late 1990s, scientists learned that cannabinoid signage can also regulate neurogenesis in adults (i.e. the growth of brain cells) and the migration of stem cells. 

We also know that following strokes and other neurological traumas, high levels of endocannabinoids are released in the brain, testifying to the neuroprotective properties of ECS, which are described by Professor Mechoulam as:

A general protection network, which works jointly with the immune system and various other physiological systems.

Professor Mechoulam

Mechoulam's discoveries, worthy of the Nobel nomination, posed a direct challenge to scientific orthodoxy by revealing that the brain has a natural repair kit, an innate mechanism of protection and regeneration that can heal brain cells.

The cannabinoid receptors CB1 & CB2

Cannabinoid receptors are present throughout the body, embedded in cell membranes; it is believed to be among the most numerous receptor systems.

When cannabinoid receptors are stimulated, they initiate a variety of physiological processes.

The two classic cannabinoid receptors are: CB1 & CB2.

Many tissues contain both CB1 and CB2 receptors, each linked to a different action.

Other receptor classes besides CB1 and CB2 are now being studied as inherent in the Endocannabinoid System, such as the class of ionic vanilloid receptors (TRPs), "orphan" receptors (GPR55, GPR18, GPR3, GPR6), nuclear receptors PPARs and many more.

 Where cannabinoid receptors are distributed

 Initially identified in 1988 thanks to the work of Allyn Howlett and William Devane, cannabinoid receptors were found to be much more abundant in the brain than practically any other type of receptor. 

Cannabinoid receptors are widely and variously distributed in the brain and other parts of the body, and therefore cannabinoids have a vast therapeutic profile.


The CB1 receptor is expressed in the central nervous system (brain) and peripheral (nerves) and other peripheral organs. CB1 receptors are present in lower densities in the heart, lungs, testes, ovary, bone marrow, thymus, uterus and immune cells.

CB2 receptors are mainly expressed at high density on cells of the immune system, including macrophages, mast cells and spleen. In the central nervous system they are mainly found in the spinal cord.

What functions do cannabinoid receptors perform? 

Using genetically modified rodents so that their cannabinoid receptors are missing (a standard procedure in scientific research that allows you to understand the functions of the receptors themselves), researchers have been able to demonstrate that cannabinoid-based compounds can alter the progression of diseases and attenuate experimentally induced symptoms.

The so-called "animal models" of osteoporosis, for example, were created in normal mice and in "knockout" mice (without cannabinoid receptors).

When a synthetic cannabinoid was administered to both groups of mice with osteoporosis, bone damage was mitigated in normal mice but not in those without cannabinoid receptors - highlighting that cannabinoid receptors are instrumental in regulating bone density.

In fact, a group of German researchers later found that the activation of CB2 receptors restrains the formation of cells that reabsorb the bone (known as osteoclasts), down-regulating, that is, decreasing the precursors of osteoclasts and reversing the balance in favor osteoblasts, i.e. cells that facilitate bone formation. 

Other experiments established that the signs triggered by cannabinoid receptors modulate pain, inflammation, appetite, glucose metabolism, gastrointestinal motility and sleep cycles, along with the rhythms of immune cells, hormones, and other neurotransmitters that alter the mood, such as serotonin, dopamine and glutamate.

How does a cannabinoid receptor work?

Retrograde signage works as an inhibitory feedback system that tells cells to "cool down" when they are getting too active.

When stimulated by THC or its endocannabinoid "cousins", cannabinoid receptors trigger a cascade of biochemical changes at the cellular level that puts the brakes on excessive physiological activity.

Endocannabinoids are the only neurotransmitters that take part in "retrograde" signage, a form of intracellular communication "on the contrary", in which stimulation starts from the post-synaptic neuron and which reduces the immune response, reduces inflammation, relaxes the muscles , decreases blood pressure, dilates the pathways of the bronchi and normalizes the over-stimulated nerves (as in neuropathic pain, or epilepsy). 

Endocannabinoids: Anandamide & 2 ‐ AG

What is an endocannabinoid?

The endocannabinoids, molecules that our body produces, activate their receptors, which are present throughout the body: in the brain, organs, connective tissues, glands and immune cells.

The two best studied endocannabinoid molecules are called Anandamide (AEA) and 2-Arachidonoylglycerol (2-AG).

These molecules are synthesized when necessary from arachidonic acid derivatives in the cell membrane, have a local effect and a short bioavailability. They are in fact rapidly degraded by specific enzymes for endocannabinoids (or called fatty acid amide hydrolase, FAAH, and monoacylglycerol lipase, MAGL). 

Chemically, endocannabinoids are eicosanoids (20 carbon atoms fatty acids), and for this reason during the ICRS Symposium of 2014 in Baveno, on Lake Maggiore, it was proposed to change the nomenclature of "endocannabinoids" to "eicosanoids" in order to prevent the stigma surrounding the Cannabis plant for therapies based on these molecules. However, this change never occurred.

What functions do endocannabinoids perform?

Formed "on order" (on request) from fatty acids in areas in need, Anandamide and 2-AG impact the organism in "mainly local and specific", says Mechoulam. “Their actions are ubiquitous. They are involved in most of the physiological systems examined ".

Endocannabinoids are protagonists of the multidimensional biochemical balance ability of life, known as homeostasis

 Robert Melamede

Says international microbiologist and medicinal cannabis activist Robert Melamede, who describes the Endocannabinoid system as the "master broker": in continuous multitasking, adjusting and readjusting the complex network of molecular thermostats that controls our physiological rhythm. 

Endocannabinoids are also neuromodulators, allowing communication and coordination between different types of cells.

For example, when we get hurt, cannabinoids can be found in the area where there is a wound, the function of which is:

●     reduce the release of activators and sensitizers from injured tissue

●     stabilize nerve cells to prevent them from discharging at excessively high frequencies 

●     calm the nearby immune cells to prevent the release of pro-inflammatory substances

These are three different mechanisms of action, on three different types of cells for a single purpose: to minimize the pain and damage caused by the wound. 

To learn more about endocannabinoids as analgesics, we recommend reading "Pain and endocannabinoids: word to the neuropharmacologist"

What is clinical endocannabinoid deficiency?

Endocannabinoid deficiency can result from too few cannabinoid receptors or insufficient presence of Anandamide and / or 2-AG.

Individuals have different congenital levels and sensitivity of endocannabinoids. 

The human immune system, one of the wonders of physiology, ignites like a furnace when fever is needed to fry a virus or bacterial invasion. When the job is done, endocannabinoid signage lowers the flame, cools the fever, and restores homeostasis.

Cannabinoids (endogenous, plant or synthetic) are anti-inflammatory and literally cool the body. But if the feedback circuit is out of control, if the pilot lights too high fires, if the immune system reacts excessively to chronic stress or confuses his body for a foreign body, then the scenario is predisposed to the development of an autoimmune disease or an inflammatory pathology.

Whether it is due to a poor quality diet, lack of exercise, environmental toxins or genetic factors, endocannabinoid deficits are associated with a reduced ability or inability to adapt to chronic stress.

Prolonged exposure to stress exhausts the tone of endocannabinoid signage and this, in turn, generates unfavorable effects for a plethora of physiological processes.

The neurologist and researcher on Medicinal Cannabis Ethan Russo first hypothesized that the "clinical deficiency from endocannabinoids" is the basis of migraine, fibromyalgia, chronic inflammation of the intestine (MICI) and a group of other conditions, which respond favorably to cannabinoid-based therapies. 

Deficiencies in endocannabinoid enzymes can also have serious effects on pregnancies, we know that a deficiency of FAAH, with a consequent increase in Anandamide can cause spontaneous abortions; infant colic has been attributed to a lack of endocannabinoids.

Ethan Russo, neurologist and medical cannabis researcher


The Endocannabinoid System is a complex set of circuits that coordinates many other physiological systems. In this article we have summarized the main knowledge.