The Endocannabinoid System ECS – Introduction and Mechanism 2026

The endocannabinoid system (ECS) is one of the youngest discoveries in mammalian physiology and one of the most widely distributed regulatory systems in the body. The first endogenous ligand of cannabinoid receptors, anandamide (AEA), was isolated by Devane, Hanus, and Mechoulam only in 1992 (Devane et al., Science, 1992). Since then, science has cataloged over 30,000 publications describing the ECS.

This system regulates homeostasis: temperature, mood, pain, sleep, appetite, immunity, and metabolism. The genes for CB1 and CB2 receptors have been evolutionarily conserved for over 600 million years (McPartland et al., PMC, 2006). This means that the ECS has accompanied vertebrates since the beginning of their evolution, and phytocannabinoids from cannabis fit into mammalian receptors by chance, not by design.

In this pillar guide, we describe the mechanism of ECS action at the molecular level: CB1 and CB2 receptors, endogenous lipid ligands AEA and 2-AG, synthesis and degradation enzymes (FAAH, MAGL), retrograde signaling, the clinical endocannabinoid deficiency theory (CECD) by Russo, and the allosteric modulation of CB1 by CBD described in the British Journal of Pharmacology in 2015.

KEY INFORMATION
– The ECS consists of three pillars: receptors (CB1, CB2 and auxiliary), endogenous lipid ligands (AEA, 2-AG) and enzymes (FAAH, MAGL).
– The first endocannabinoid, anandamide, was described by Devane, Hanus, and Mechoulam in 1992 (Science).
– The concentration of 2-AG in the brain is approximately 200 times higher than that of AEA (Sugiura, PMC, 2006), making it the dominant CB1 agonist.
– CBD is a negative allosteric modulator of CB1 (Laprairie et al., BJP, 2015), not an orthosteric agonist.
– The CECD theory (Russo, 2016) suggests a role for ECS dysfunction in migraine, fibromyalgia, and IBS.
– Retrograde signaling is a unique ECS mechanism that protects neurons from excitotoxicity.

broad spectrum category

What is the endocannabinoid system and what role does it play?

The endocannabinoid system is a lipid signaling network that maintains homeostasis by regulating the release of neurotransmitters and cytokines. According to a review in Pharmacological Reviews from 2010, the ECS regulates at least 12 physiological systems: mood, pain, sleep, appetite, immunity, reproduction, motor function, and many others (Pertwee, Pharmacol Rev, 2010). It acts like a biological dimmer, regulating the intensity of signals.

Homeostasis is the ability of the body to maintain stable internal conditions despite changes in the environment. The ECS intervenes when the body deviates from a state of balance: after stress, injury, infection, sleep deprivation, or overheating. Endocannabinoids are synthesized on demand from membrane phospholipids and act locally, in the vicinity of the synthesis site.

Unlike classic neurotransmitters such as dopamine or serotonin, endocannabinoids are not stored in synaptic vesicles. They are produced rapidly and undergo enzymatic degradation just as quickly. This "on-demand" mechanism ensures precise signaling in both time and space. This is a unique feature of the ECS on a physiological scale.

Four Pillars of the Endocannabinoid System

The system is based on four elements. First, receptors: CB1 and CB2, plus auxiliary GPR55, TRPV1, and PPARγ. Second, endogenous ligands: anandamide (AEA), 2-arachidonoylglycerol (2-AG), virodhamine, NADA, OEA, PEA. Third, synthesis enzymes: NAPE-PLD for AEA, DAGLα/β for 2-AG. Fourth, degradation enzymes: FAAH for AEA, MAGL for 2-AG.

All four pillars work together dynamically. A biological stimulus (neuron depolarization, oxidative stress, injury) activates synthesis. The endocannabinoid binds to the receptor, triggering a G-protein cascade, modifying synaptic transmission. Then, enzymes quickly inactivate the signal. The entire cycle lasts milliseconds to seconds in the synapse and minutes in peripheral tissues.

definition of ECS

The endocannabinoid system is a lipid signaling network that includes CB1, CB2, and auxiliary receptors (GPR55, TRPV1, PPARγ), endogenous ligands AEA and 2-AG, as well as enzymes NAPE-PLD, DAGL, FAAH, and MAGL. The ECS regulates at least 12 physiological systems, acting through retrograde signaling described in Nature in 2001 (Wilson and Nicoll, Nature, 2001).

What was the history of the discovery of ECS from 1964 to 1995?

The history of ECS is three decades of groundbreaking discoveries between 1964 and 1995. Raphael Mechoulam and Yechiel Gaoni isolated the structure of THC in 1964 at the Hebrew University (Gaoni and Mechoulam, JACS, 1964). This was the foundation for all subsequent discoveries in the field of cannabinoids. Without knowledge of the ligand, there would be no receptor research.

In 1988, Allyn Howlett and William Devane at St. Louis University identified a specific binding site for CP-55,940 (a synthetic analogue of THC) in the rat brain (Devane et al., Mol Pharmacol, 1988). Two years later, Lisa Matsuda et al. cloned the CB1 receptor and published the sequence in Nature in 1990 (Matsuda et al., Nature, 1990).

The year 1992 brought another breakthrough. Devane, Hanus, and Mechoulam described the first endogenous ligand of the CB1 receptor, named anandamide from the Sanskrit "ananda" (bliss). Three years later, Mechoulam and Ben-Shabat identified the second major endocannabinoid: 2-arachidonoylglycerol (Mechoulam et al., Biochem Pharmacol, 1995). These two discoveries closed the basic architecture of the ECS.

Cloning of the CB2 receptor in 1993

Sean Munro, Kerrie Thomas, and Mahmoud Abu-Shaar from the University of Cambridge cloned the second cannabinoid receptor in 1993, publishing the results in Nature (Munro et al., Nature, 1993). CB2 exhibits 44% sequence homology with CB1 and has a different distribution in the body. This is a key functional difference between the two receptors.

The opening of this chapter allowed for an understanding of why cannabinoids modulate both the nervous system (CB1) and the immune system (CB2). Previously, scientists treated cannabis solely as neuropsychopharmacology. After 1993, it became clear that cannabinoids affect the entire physiology, not just the brain.

FAAH and MAGL: enzymes discovered between 1996 and 2002

Cravatt et al. isolated FAAH in 1996, describing the mechanism of hydrolysis of AEA to arachidonic acid and ethanolamine (Cravatt et al., Nature, 1996). MAGL was characterized in the context of 2-AG degradation by Dinh, Carpenter, and Piomelli in 2002 (Dinh et al., PNAS, 2002).

These two enzymes have become therapeutic targets. FAAH inhibitors (e.g., URB597, PF-04457845) have been studied as analgesics and anxiolytics. MAGL inhibitors (JZL184) have been tested in models of inflammation and neuropathic pain. The tragic incident with BIA 10-2474 in France in 2016 halted some programs, but the area remains active in academic pharmacology.

What are CB1 receptors and where are they located?

CB1 receptors are G protein-coupled receptors (GPCR) of the Gi/o type. Their density in the hippocampus, prefrontal cortex, striatum, and cerebellum exceeds 100 times the density of mu opioid receptors in some regions (Mackie, BJP, 2008). This makes CB1 one of the most abundant GPCRs in the mammalian central nervous system.

CB1 localizes primarily to the presynaptic axon terminals of GABAergic and glutamatergic neurons. It acts as a "brake" on neurotransmitter release. CB1 activation reduces calcium influx through N- and P/Q-type channels, which reduces synaptic vesicle exocytosis. The effect is immediate and reversible.

Outside the central nervous system, CB1 is found in the liver (hepatocytes, Kupffer cells), adipose tissue, skeletal muscles, gastrointestinal tract, heart, blood vessels, gonads, and bones. This peripheral presence explains why the CB1 antagonist rimonabant (Acomplia) effectively reduced body weight but was withdrawn due to psychiatric effects.

Neuronal subpopulations expressing CB1

The highest expression of CB1 is found in GABAergic interneurons containing cholecystokinin (CCK+ interneurons) in the hippocampus and cortex. These cells control theta rhythm and network synchronization. Modulation of CB1 on these interneurons explains the effects of THC on short-term memory and time perception.

Another important subpopulation is glutamatergic neurons in the cortex and hippocampus. Their CB1 is expressed to a lesser extent, but its activation protects against excitotoxicity caused by excess glutamate. Selective removal of CB1 from these neurons in mice exacerbates cell death after stroke (Marsicano et al., Nature, 2003), confirming the neuroprotective role of the receptor.

CB1 receptors

CB1 receptors are primarily present on the presynaptic terminals of GABAergic and glutamatergic neurons in the central nervous system. Their activation inhibits neurotransmitter release by reducing calcium influx, which constitutes a retrograde signaling mechanism (Wilson and Nicoll, Nature, 2001). The density of CB1 in the hippocampus is among the highest of GPCRs in the mammalian brain.

What are CB2 receptors and what role do they play in immunity?

CB2 receptors are primarily located in immune system cells, where they modulate the inflammatory response. Their expression is 10-100 times higher in B and NK lymphocytes than in T lymphocytes (Galiegue et al., Eur J Biochem, 1995, cited in PMC, 2010). This makes CB2 a strategic target for immunomodulatory therapies.

Activation of CB2 inhibits the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and increases the secretion of anti-inflammatory cytokines (IL-10). The mechanism works through a Gi/o type G-protein cascade, inhibiting adenylate cyclase and modulating the NF-κB pathway. This is why CB2 is a target in research on autoimmune diseases: multiple sclerosis, rheumatoid arthritis, and IBD.

In the central nervous system, CB2 is expressed primarily on microglia, the resident macrophages of the brain. Expression is low under physiological conditions but increases dramatically during neuroinflammation. This mechanism of "induced expression" explains its therapeutic potential in Alzheimer's disease, Parkinson's disease, and ALS.

Osteoblasts and osteoclasts express functional CB2 receptors. Their activation reduces bone resorption and supports mineralization, as confirmed by studies in mouse models of osteoporosis (Ofek et al., PNAS, 2006). This opens a potential avenue for postmenopausal osteoporosis therapy, although clinical studies in humans are still limited.

In the gut, CB2 is expressed on immune cells of the mucosa, in Paneth cells, and on neurons of the enteric nervous system. Activation of CB2 reduces gut motility in inflammatory states and modulates intestinal barrier permeability. This is one of the mechanisms that explains the beneficial effects of cannabinoids in ulcerative colitis and Crohn's disease.

Auxiliary receptors: GPR55, TRPV1, PPARγ

In addition to CB1 and CB2, endocannabinoids interact with auxiliary receptors. GPR55, cloned in 1999, is sometimes referred to as the "third cannabinoid receptor," although it is activated more strongly by the phospholipid LPI than by AEA. The TRPV1 (vanilloid) receptor responds to anandamide at high concentrations, which explains the analgesic effect of AEA independent of CB1.

In addition to CB1 and CB2, endocannabinoids interact with accessory receptors. GPR55, cloned in 1999, is sometimes called the "third cannabinoid receptor," although it is activated more strongly by the phospholipid LPI than by AEA. The TRPV1 (vanilloid) receptor responds to high concentrations of anandamide, which explains the CB1-independent analgesic effect of AEA.

What is anandamide (AEA) and how does it work?

Anandamide (N-arachidonoylethanolamine, AEA) is the first discovered endogenous ligand of cannabinoid receptors. Its concentration in rat brain tissues ranges from 30-50 pmol/g (

Sugiura, PMC, 2006). This concentration is sufficient for tonic modulation of synapses but does not saturate receptors, allowing for dynamic regulation of the signal.AEA is a partial agonist of the CB1 receptor and a weak agonist of CB2. Partial agonism means that AEA activates the receptor to a lesser extent than THC (a full agonist) and significantly less than synthetic agonists like WIN 55,212-2. This partial action protects against excessive stimulation and explains why endogenous levels of AEA do not produce psychoactive effects.

The synthesis of AEA occurs from N-arachidonoylphosphatidylethanolamine (NAPE) with the involvement of NAPE-PLD, a phospholipase D specific for NAPE. Calcium stimuli, neuron depolarization, and activation of metabotropic receptors trigger synthesis. After fulfilling its task, AEA returns to the cell via a transporter (FAAT) and is hydrolyzed by FAAH.

Physiological functions of anandamide

AEA regulates mood, motivation, memory, and pain perception. Polymorphisms in the FAAH gene (e.g., C385A variant) correlate with elevated levels of AEA and reduced anxiety (

Dincheva et al., PNAS, 2015). Individuals with this variant extinguish fear responses more quickly, suggesting a role for AEA in PTSD therapy."Runner's high" is partly the result of elevated AEA during intense physical exertion. A 2003 study showed that AEA levels in plasma double after a 50-minute run (

„The "runner's high" is partly due to increased AEA during intense exercise. A 2003 study found that plasma AEA levels doubled after a 50-minute run (, 2003). This explains the beneficial effects of regular exercise on mood and well-being.Anandamide in chocolate and diet

Dark chocolate contains AEA and two congeners (N-oleoylethanolamine and N-linoleoylethanolamine), which inhibit the breakdown of AEA by competing for FAAH. The concentrations are too low to produce psychoactive effects but sufficient for gentle modulation of the ECS after a meal. This partly explains the "calming" effect of chocolate and cocoa.

Dark chocolate contains AEA and two congeners (N-oleylethanolamine and N-linoleylethanolamine), which inhibit AEA degradation by competing for FAAH. Concentrations are too low to produce psychoactive effects but are sufficient to gently modulate the ECS after a meal. This partially explains the "calming" effect of chocolate and cocoa.

What is 2-arachidonoylglycerol (2-AG)?

2-arachidonoylglycerol (2-AG) is the second major endocannabinoid, discovered by Mechoulam and Ben-Shabat in 1995 (

, 1995). Its concentration in the brain is about 200 times higher than that of AEA, reaching 5-10 nmol/g of tissue. This makes 2-AG the dominant agonist of both cannabinoid receptors in physiology.Mechoulam et al., Biochem Pharmacol2-AG is a full agonist of both CB1 and CB2. Unlike AEA, it induces stronger and fuller receptor activation. Synthesis occurs from diacylglycerols (DAG) with the involvement of two isoforms of DAGL: DAGLα (mainly in neurons) and DAGLβ (mainly in immune cells). Both isoforms are activated by calcium influx.

The degradation of 2-AG is tightly controlled. MAGL accounts for 85% of degradation in the brain, while ABHD6 and ABHD12 contribute in smaller amounts (

Blankman et al., Chem Biol, 2007). Inhibition of MAGL by JZL184 raises levels of 2-AG up to 8 times, leading to strong analgesic and anxiolytic effects in animal models.Retrograde signaling and 2-AG

2-AG is a key mediator of retrograde signaling at synapses. After depolarization of the postsynaptic neuron, calcium activates DAGLα. Newly synthesized 2-AG diffuses through the synaptic membrane to the presynapse, where it binds to CB1 and inhibits the release of GABA or glutamate. The entire cycle lasts 200-500 ms.

This mechanism has been described as DSI (depolarization-induced suppression of inhibition) and DSE (depolarization-induced suppression of excitation) by Wilson and Nicoll in 2001 (

, 2001). DSI/DSE allows the postsynaptic neuron to control its own input, a kind of synaptic feedback.Wilson and Nicoll, Nature2-AG and appetite and metabolism

The concentration of 2-AG in the hypothalamus increases during hunger and decreases after a meal. Activation of CB1 by 2-AG in the arcuate nucleus of the hypothalamus increases appetite and taste preference for high-calorie foods. This mechanism explains the "munchies" effect after THC, as THC acts on the same receptors as endogenous 2-AG.

Hypothalamic 2-AG concentrations increase during hunger and decrease after a meal. CB1 activation by 2-AG in the arcuate nucleus of the hypothalamus increases appetite and taste preference for high-calorie foods. This mechanism explains the "munchies" effect of THC, as THC acts on the same receptors as endogenous 2-AG.

How do FAAH and MAGL enzymes work in the ECS?

FAAH and MAGL enzymes act as "switches" for the endocannabinoid signal. FAAH (fatty acid amide hydrolase) hydrolyzes AEA to arachidonic acid and ethanolamine. MAGL (monoacylglycerol lipase) accounts for 85% of 2-AG degradation in the brain (

FAAH and MAGL enzymes are the "off switches" of the endocannabinoid signal. FAAH (fatty acid amide hydrolase) hydrolyzes AEA to arachidonic acid and ethanolamine. MAGL (monoacylglycerol hydrolase) is responsible for 85% degradation of 2-AG in the brain (, 2007). Inhibition of MAGL by JZL184 raises levels of 2-AG up to 8 times, leading to strong analgesic and anxiolytic effects in animal models.FAAH is a membrane enzyme located on the endoplasmic reticulum. It is abundant in the brain (cortex, hippocampus, cerebellum), liver, and intestines. The C385A polymorphism (rs324420) reduces FAAH activity by about 50% and correlates with better stress tolerance (

, 2015). This variant occurs in about 20% of the European population., 2015). Individuals with this variant extinguish fear responses more quickly, suggesting a role for AEA in PTSD therapy.MAGL is a cytosolic enzyme, although part of the pool binds to membranes. It is found in neurons, astrocytes, and immune cells. Selective MAGL inhibitors (JZL184, MJN110) are being intensively studied as analgesics because they raise 2-AG tone without the risk of tolerance typical of CB1 agonists.

FAAH and MAGL inhibitors as drugs

The FAAH inhibitor PF-04457845 reached phase III clinical trials in pain from osteoarthritis. Preliminary results showed good tolerance and moderate efficacy. The MAGL inhibitor ABX-1431 entered trials for Tourette syndrome and chronic pain. Both classes are promising, although no drug from this group has yet been registered.

The FAAH inhibitor PF-04457845 has reached Phase III clinical trials for pain associated with osteoarthritis. Preliminary results have shown good tolerability and moderate efficacy. The MAGL inhibitor ABX-1431 has entered trials for Tourette syndrome and chronic pain. Both classes show promise, although no drug in this class has yet been approved.

ECS enzymes

FAAH and MAGL control the duration of the endocannabinoid signal. MAGL accounts for 85% of 2-AG hydrolysis in the brain (

, 2007). The FAAH C385A polymorphism reduces enzyme activity by about 50% and correlates with better stress tolerance in genetic studies of the European population (Dincheva et al., PNAS, 2015)., 2007). Inhibition of MAGL by JZL184 raises levels of 2-AG up to 8 times, leading to strong analgesic and anxiolytic effects in animal models.Cannova CBG 15% - pure "mother of cannabinoids"

Retrograde signaling is a unique mechanism of the ECS, where the signal goes backward, from the postsynaptic neuron to the presynaptic one. Classical neurotransmission occurs in the opposite direction. The DSI/DSE (depolarization-induced suppression) mechanism was described by Wilson and Nicoll in Nature in 2001 (

, 2001). This is a revolution in understanding synaptic physiology.Wilson and Nicoll, NatureThe mechanism works as follows. The postsynaptic neuron depolarizes, calcium-dependent channels open. The increase in intracellular Ca²⁺ activates DAGLα, which synthesizes 2-AG from membrane diacylglycerols. 2-AG diffuses through the membrane and crosses the synaptic cleft backward, toward the presynapse.

In the presynapse, 2-AG binds to the CB1 receptor. Activation of CB1 by Gi/o inhibits adenylate cyclase, reduces cAMP, and blocks N and P/Q type calcium channels. Less calcium in the presynapse means less exocytosis of synaptic vesicles. The neurotransmitter signal (GABA or glutamate) weakens. The neuronal network is modulated.

Functional significance of DSI and DSE

DSI reduces GABAergic inhibition, effectively "releasing the brake" on pyramidal neurons in the hippocampus. This may enhance LTP (long-term potentiation) and memory consolidation under specific conditions. DSE reduces glutamatergic excitation, protecting neurons from excitotoxicity. Together, both mechanisms constitute a local system for controlling synaptic excitability.

DSI reduces GABAergic inhibition, meaning it "releases the brake" on the pyramidal neuron in the hippocampus. This may enhance long-term potentiation (LTP) and memory consolidation under specific conditions. DSE reduces glutamatergic excitation, protecting neurons from excitotoxicity. Together, these two mechanisms constitute a local control system for synaptic excitability.

Other forms of synaptic plasticity dependent on ECS

In addition to DSI/DSE, the ECS mediates endocannabinoid-dependent long-term depression (eCB-LTD). This mechanism operates over minutes and hours, while DSI/DSE lasts seconds. eCB-LTD is significant in motor learning, plasticity of visual circuits, and regulation of behavioral habits.

A synapse with an active ECS is not a static system but a dynamic structure. Endocannabinoids are synthesized "in real-time" in response to neuronal activity and degraded when activity decreases. This "feedback on demand" mechanism explains why the ECS is so precise in regulating brain homeostasis.

A synapse with an active ECS is not a static system, but a dynamic structure. Endocannabinoids are synthesized "in real time" in response to neuronal activity and degraded when activity decreases. This "feedback on demand" mechanism explains why the ECS is so precise in regulating brain homeostasis.

The ECS regulates at least 12 physiological systems, as confirmed by Pertwee's review in Pharmacological Reviews from 2010 (

, 2010). Major areas include mood, pain, sleep, appetite, immunity, reproduction, motor function, neuroprotection, metabolism, cardiovascular system, bones, and skin.Pertwee, Pharmacol RevEach of these systems has its own specific patterns of CB1/CB2 expression and its own dominant endocannabinoids. In the brain, 2-AG and CB1 dominate. In immunity, AEA and CB2 dominate. In the gut, both receptors are important, and in the skin, PEA and PPARγ are particularly prominent. This diversity makes the ECS a universal regulatory mechanism.

Dysfunction of the ECS can manifest in very different ways, depending on the affected system. Migraines, fibromyalgia, IBS, and chronic fatigue syndrome are classic examples of syndromes in which Russo's CECD theory postulates a role for ECS dysfunction. Newer studies add treatment-resistant depression and some neurodevelopmental disorders.

Mood and anxiety modulation

CB1 receptors in the prefrontal cortex, amygdala, and hippocampus modulate anxiety responses. Low ECS tone correlates with anxiety and depression. The FAAH C385A polymorphism, which raises AEA by about 50%, correlates with lower anxiety and better fear extinction (Dincheva et al., PNAS, 2015). This is why FAAH inhibitors are being studied in PTSD and generalized anxiety.

2-AG in the amygdala modulates the consolidation of aversive memories. Increasing 2-AG tone through MAGL inhibitors weakens the expression of traumatic memory in animals. This "pharmacological extinction" approach is one of the most promising strategies in treating PTSD resistant to classical antidepressants.

2-AG in the amygdala modulates the consolidation of aversive memories. Increasing 2-AG tone with MAGL inhibitors attenuates the expression of traumatic memories in animals. This "pharmacological extinction" approach is one of the most promising strategies for treating PTSD resistant to traditional antidepressants.

Pain control

Endocannabinoids are particularly effective in neuropathic pain, where classical opioids often fail. The "stress-induced analgesia" mechanism is partly mediated by increased AEA in the PAG after exposure to acute stress. This is one of the examples of the evolutionary role of the ECS in the survival of the organism.

Endocannabinoids are particularly effective in neuropathic pain, where classical opioids often fail. The mechanism of "stress-induced analgesia" is partially mediated by an increase in AEA in the PAG following exposure to acute stress. This is one example of the evolutionary role of the ECS in organismal survival.

The ECS regulates sleep rhythms by modulating monoaminergic neurons in the brainstem. Activation of CB1 in the dorsal raphe nuclei reduces serotonergic activity and prolongs REM sleep. AEA promotes REM sleep, while 2-AG has a greater influence on NREM phases. Hence the different subjective effects of phytocannabinoids on sleep.

In metabolism, the ECS regulates energy balance at three levels: central (appetite through the hypothalamus), hepatic (de novo lipogenesis), and peripheral (adipocytes, muscles). Obesity is associated with elevated ECS tone in adipose tissue. Selective peripheral CB1 antagonists that do not cross the blood-brain barrier are currently being tested as a safer alternative to rimonabant.

Immunity and inflammation

CB2 dominates in immune cells, where it inhibits the migration of leukocytes to sites of inflammation, reduces the production of pro-inflammatory cytokines, and induces apoptosis of activated lymphocytes. Together, these mechanisms suppress excessive inflammatory responses. Therefore, CB2 is a target for research on autoimmune diseases: MS, RA, psoriasis, and IBD.

Selective CB2 agonists, such as HU-308 and JWH-133, exhibit anti-inflammatory effects in animal models without the psychoactive effects typical of CB1. This makes them attractive candidates for drugs, although no selective CB2 agonist has yet been registered for clinical use in humans.

What is the clinical endocannabinoid deficiency (CECD) according to Russo?

The theory of clinical endocannabinoid deficiency (CECD) was formulated by Dr. Ethan Russo in 2004 and updated in 2016 in Cannabis and Cannabinoid Research (

Russo, Cannabis and Cannabinoid Research, 2016). The hypothesis suggests that migraine, fibromyalgia, and irritable bowel syndrome may result from reduced ECS tone.Russo noted that these three conditions share common features: a lack of structural changes in classical imaging studies, resistance to standard medications, and frequent co-occurrence in the same patient. When classical pathophysiology does not explain symptoms, the hypothesis of ECS signaling disorders becomes a logical candidate.

Supporting data for CECD include reduced levels of AEA in the cerebrospinal fluid of patients with chronic migraine (Sarchielli et al., Neuropsychopharmacology, 2007). In female patients with fibromyalgia, lower levels of 2-AG in serum have been observed. In IBS, polymorphisms in the CNR1 (CB1) and FAAH genes have been described that correlate with symptom severity.

Migraine and ECS

Migraine is one of the best-studied areas of the CECD hypothesis. Russo showed that patients with chronic migraine have reduced AEA in CSF. Activation of CB1 in the trigeminal nucleus inhibits the release of CGRP, a key mediator of migraine. Therefore, low ECS tone promotes uncontrolled activation of the trigeminal-vascular pathway.

Clinical studies on CBD and CBG in migraine are currently underway. Preliminary results indicate the potential of both cannabinoids in reducing the frequency and severity of attacks, although randomized clinical trials in large patient populations are still limited. The mechanism of action likely involves modulation of serotonin, CGRP, and ECS tone simultaneously.

Fibromyalgia and IBS in light of CECD

Fibromyalgia combines generalized musculoskeletal pain, fatigue, sleep disturbances, and cognitive symptoms. Russo argues that this symptom complex corresponds to a wide spectrum of functions modulated by the ECS. Low levels of endocannabinoids may explain why patients with fibromyalgia often respond positively to phytocannabinoid supplementation.

IBS (irritable bowel syndrome) is characterized by dysregulation of the gut-brain axis. CB1 and CB2 receptors are currently present in neurons of the enteric nervous system, immune cells of the mucosa, and Paneth cells. Modulation of the ECS may affect gut motility, barrier permeability, and interactions with the microbiota. This is another pathway where CECD finds support in the data.

CECD

Russo's theory of clinical endocannabinoid deficiency (CECD) posits that migraine, fibromyalgia, and IBS result from reduced ECS tone. Patients with chronic migraine exhibit reduced levels of anandamide in cerebrospinal fluid (Sarchielli et al., Neuropsychopharmacology, 2007). An update of the hypothesis appeared in Cannabis and Cannabinoid Research in 2016 (

Russo, CCR, 2016)., 2016).

Phytocannabinoids from cannabis (THC, CBD, CBG, CBN, CBC) modulate the ECS through various pharmacological mechanisms. THC is a partial agonist of CB1 and CB2. CBD is a negative allosteric modulator of CB1, as demonstrated by Laprairie et al. in the British Journal of Pharmacology in 2015 (

Laprairie et al., BJP, 2015). CBG activates α2-adrenergic receptors and weakly CB1.These pharmacological differences explain the varied clinical effects. THC induces psychoactivity and euphoria, while CBD does not. CBD can even weaken the effects of THC through allosteric modulation, as confirmed by studies on the co-administration of both compounds. CBG exhibits a "focusing" profile rather than a sedative one, resulting from its action on adrenergic receptors.

These pharmacological differences explain the varying clinical effects. THC induces psychoactivity and euphoria, while CBD does not. CBD can even mitigate the effects of THC through allosteric modulation, as confirmed by studies on co-administration of both compounds. CBG exhibits a "focusing" rather than a sedative profile, which results from its action on adrenergic receptors.

, 2011). Full-spectrum cannabis extract exhibits stronger effects than isolates of individual cannabinoids. This justifies the popularity of broad spectrum and full spectrum oils.Russo, BJPCBD as an allosteric modulator of CB1

Classical ligand binding to the receptor occurs at the orthosteric site. CBD does not bind orthosterically to CB1 with significant affinity. Instead, CBD binds at an allosteric site, which is separate from the binding site of THC. This interaction changes the conformation of the receptor and lowers its activity when stimulated by THC or endogenous 2-AG.

Negative allosteric modulation means that CBD does not block the signal but merely "dials it down." This is a gentler mechanism than orthosteric antagonism. Hence, CBD has a good safety profile and lacks psychoactive effects even at high doses. The WHO recognized CBD as a compound "well tolerated with a good safety profile" in a review from 2018 (

Negative allosteric modulation means that CBD doesn't block the signal, but merely "mutes" it. This is a more gentle mechanism than orthosteric antagonism. Hence, CBD's good safety profile and lack of psychoactive effects even at high doses. The WHO deemed CBD a "well-tolerated compound with a good safety profile" in a 2018 review (, 2018)., 2018).

CBD also inhibits FAAH, albeit with moderate strength. The net effect is elevated endogenous AEA levels in tissues, supporting ECS tone without direct receptor activation. This "tonic enhancement" mechanism is one of the theoretical explanations for why CBD acts anxiolytically and analgesically without psychoactivity.

CBD also inhibits FAAH, albeit with moderate potency. The net effect is increased endogenous AEA in tissues, which supports ECS tone without directly activating receptors. This "tonic enhancement" mechanism is one theoretical explanation for CBD's anti-anxiety and analgesic effects without psychoactivity.

THC, CBG, and other phytocannabinoids

THC is a partial agonist of CB1 with high affinity (Ki about 10 nM for CB1). This explains the psychoactive effects: euphoria, perception, increased appetite, analgesia. THC also activates CB2, contributing to the anti-inflammatory effect. Polish law allows trace amounts of THC (up to 0.3%) in hemp products.

CBG weakly activates CB1 and CB2 but strongly binds to the α2-adrenergic receptor. It also inhibits AEA reuptake and modulates 5-HT1A. CBN is formed from oxidized THC and has 5-10 times lower affinity for CB1 than THC. CBC primarily acts on TRPV1 and TRPA1. Each of these cannabinoids has a different pharmacological profile, although all indirectly affect the ECS.

SOOL CBD Oil 10% - stronger support for ECS

Unique observation: CBD is most often described as a "natural medicine" competing with anxiolytic drugs. However, at the molecular level, CBD doesn't directly activate receptors but rather enhances the body's own endocannabinoid tone. This is a strategy of "tuning the system" rather than "overriding the system." This explains its gentle and cumulative nature, requiring 2-4 weeks of regular supplementation to achieve its full effect.

How to support the endocannabinoid system naturally?

, 2003). Physical activity, omega-3 diet, cold exposure, and meditation are effective strategies for naturally supporting ECS tone., 2003). This explains the beneficial effects of regular exercise on mood and well-being.Moderate-intensity aerobic physical activity (60-70% of maximum heart rate) most strongly raises AEA. Higher intensities (above 80% HRmax) are less effective, likely due to sympathetic tone and increased cortisol. The optimal range is running, cycling, swimming for 30-50 minutes, 3-4 times a week.

A diet rich in omega-3 (DHA and EPA) provides substrates for the synthesis of AEA and 2-AG. The omega-6 to omega-3 ratio should be 4:1 or lower. The Western diet typically has a ratio of 15-20:1, which is unfavorable. Consuming fatty fish (salmon, mackerel, sardines) 2-3 times a week, plus walnuts and flaxseed, significantly improves this profile.

Beta-caryophyllene and dietary terpenes

Beta-caryophyllene is a unique terpene acting as a selective CB2 agonist (

Gertsch et al., PNAS, 2008). It is the first terpene from dietary plants that directly activates a cannabinoid receptor. It is found in black pepper, oregano, cinnamon, cloves, and hops. Daily use of these spices may subtly support CB2 tone.Other terpenes (myrcene, limonene, linalool, pinene) modulate the ECS indirectly, through effects on cell membranes and auxiliary receptors. Using fresh herbs in cooking, as well as herbal teas with lemon balm, lavender, or hops, may support the "entourage effect" at a physiological scale, although the strength of this effect is, of course, much less than in concentrated cannabis extracts.

Other terpenes (myrcene, limonene, linalool, pinene) modulate the ECS indirectly by affecting cell walls and accessory receptors. Using fresh herbs in cooking, as well as herbal teas with lemon balm, lavender, or hops, can support the "entourage effect" on a physiological scale, although the magnitude of this effect is obviously much less than that of concentrated cannabis extracts.

Chronic stress lowers AEA and 2-AG due to excess cortisol and activation of the HPA axis. Sleep deprivation acts similarly. Stress reduction practices, such as mindfulness meditation, yoga, breathing exercises, and contact with nature, support ECS tone by normalizing cortisol rhythm.

A 2019 study showed that an 8-week MBSR (mindfulness-based stress reduction) program raised AEA levels in participants' serum by 13-22%. The mechanism likely involves reducing sympathetic activity and increasing parasympathetic tone, which directly affects the release of endocannabinoids.

Cold exposure and hormesis

Cold exposure (ice baths, alternating showers) activates BAT (brown adipose tissue) and increases the secretion of endocannabinoids. The mechanism involves activation of TRPV1 and TRPM8, as well as stimulation of UCP1 in mitochondria. This is one of the mechanisms for why ice baths have become popular in sports and wellness.

Other forms of mild stress (intermittent fasting, physical exertion, sun exposure) act through similar hormetic pathways. All these stimuli, applied in moderate doses, support ECS tone by activating adaptive mechanisms. The key is "moderation" - excess becomes a chronic stressor that weakens the ECS.

Other forms of mild stress (intermittent fasting, exercise, sun exposure) operate through similar hormetic pathways. All of these stimuli, when applied in moderate doses, support ECS tone by activating adaptive mechanisms. The key is "moderate"—excess becomes a chronic stressor, which the ECS weakens.

The number of publications on ECS is growing exponentially. PubMed currently indexes over 30,000 papers with the term "endocannabinoid," and the annual increase is over 2,000 publications (

The number of publications on the ECS is growing exponentially. PubMed currently indexes over 30,000 papers with the term "endocannabinoid," and the annual growth is over 2,000 publications (PubMedEpidiolex (pure CBD) remains the only phytocannabinoid-based drug registered by the FDA, with registration in treatment-resistant childhood epilepsy (Dravet syndrome, Lennox-Gastaut syndrome, tuberous sclerosis). Sativex (THC:CBD 1:1) is available in Europe for spasticity in MS. Other cannabinoids are still in clinical trial phases.

Selective MAGL inhibitors (e.g., ABX-1431, Lu AG06466) are being studied in Tourette syndrome, multiple sclerosis, and neuropathic pain. Allosteric positive modulators of CB1 (PAMs) are candidates for safer analgesics than orthosteric agonists. Selective CB2 agonists (e.g., lenabasum) have been tested in SLE and scleroderma.

Selective MAGL inhibitors (e.g., ABX-1431, Lu AG06466) are being investigated in Tourette syndrome, multiple sclerosis, and neuropathic pain. CB1 positive allosteric modulators (PAMs) are candidates for safer analgesics than orthosteric agonists. Selective CB2 agonists (e.g., lenabasum) have been tested in SLE and scleroderma.

Polymorphisms in ECS genes affect individual responses to cannabinoid medications. The FAAH C385A variant (rs324420) increases AEA activity and correlates with better stress tolerance. CNR1 (CB1) polymorphisms influence the risk of obesity, depression, and addiction. CNR2 (CB2) polymorphisms are associated with autoimmunity and osteoporosis.

In the future, ECS genetic tests may help tailor cannabinoid medications to the individual patient's profile. Some companies already offer genetic panels for such personalization, although their clinical value is still subject to validation in prospective clinical studies.

ECS in the microbiome and gut-brain axis

Gut microbiota modulates the ECS through metabolites (bile acids, short-chain fatty acids) that affect the expression of CB1, CB2, and FAAH in the intestines. Probiotics Lactobacillus and Bifidobacterium raise ECS tone in the intestinal mucosa (

, 2020).Frontiers in Pharmacology, 2020).

In our store practice, we observe that customers are increasingly asking not about "what to buy," but about "how ECS works." Awareness of the mechanism we modulate with phytocannabinoids has significantly increased over the past 24 months. This is a positive trend, as informed supplementation yields better results than randomly trying out various products.

From the Bucha editorial office: In our in-store practice, we're seeing customers increasingly asking not "what to buy," but "how the ECS works." Awareness of the mechanism we modulate with phytocannabinoids has increased significantly over the past 24 months. This is a positive trend, as informed supplementation yields better results than randomly trying new products.

Frequently Asked Questions

The endocannabinoid system is a network of receptors, endogenous lipid ligands, and enzymes regulating the homeostasis of the body. The first CB1 receptor was cloned in 1990 (

, 1990). The first endocannabinoid, anandamide (AEA), was isolated by Devane, Hanus, and Mechoulam in 1992 (Matsuda et al., Nature, 1992).Devane et al., Science, 1992).

CB1 receptors dominate in the central nervous system, especially in the hippocampus, striatum, and cerebellum. Their density exceeds 100 times the density of mu opioid receptors in some regions (

, 2008). CB2 receptors are mainly located in immune system cells, the spleen, microglia, and bone tissue.Mackie, BJPWhat are anandamide (AEA) and 2-AG?

Anandamide (N-arachidonoylethanolamine, AEA) is the first discovered endocannabinoid, described in 1992 (Devane et al., Science). 2-arachidonoylglycerol (2-AG) was discovered by Mechoulam and Ben-Shabat in 1995. The concentration of 2-AG in the brain is about 200 times higher than that of AEA (

, 2006), making it the dominant agonist of CB1., 2006). This concentration is sufficient for tonic modulation of synapses but does not saturate receptors, allowing for dynamic regulation of the signal.How do FAAH and MAGL enzymes work in the endocannabinoid system?

FAAH (fatty acid amide hydrolase) hydrolyzes anandamide to arachidonic acid and ethanolamine. MAGL (monoacylglycerol lipase) accounts for 85% of 2-AG degradation in the brain (

, 2007). Inhibition of these enzymes raises endocannabinoid levels and is the subject of research for anxiolytic and analgesic drugs., 2007). Inhibition of MAGL by JZL184 raises levels of 2-AG up to 8 times, leading to strong analgesic and anxiolytic effects in animal models.What is Russo's theory of clinical endocannabinoid deficiency (CECD)?

CECD (Clinical Endocannabinoid Deficiency) is a hypothesis by Dr. Ethan Russo from 2004, updated in 2016 in Cannabis and Cannabinoid Research. It suggests that migraine, fibromyalgia, and irritable bowel syndrome may result from reduced ECS tone. In studies, patients with migraines exhibit reduced levels of AEA in cerebrospinal fluid (

CBD is a negative allosteric modulator of the CB1 receptor, as confirmed by studies by Laprairie et al. published in the British Journal of Pharmacology in 2015 (, 2016)., 2016).

How does CBD affect the endocannabinoid system?

, 2015). CBD does not bind orthosterically but alters the conformation of CB1, inhibiting THC activity. Additionally, CBD blocks the reuptake of anandamide and inhibits FAAH, raising the tone of endogenous endocannabinoids., 2015). CBG activates α2-adrenergic receptors and weakly CB1.Endocannabinoids are synthesized on demand in the postsynaptic neuron and move retrogradely to the presynapse, where they activate CB1, inhibiting the release of glutamate or GABA (

Retrograde signaling is a unique mechanism of the ECS, where the signal goes backward, from the postsynaptic neuron to the presynaptic one. Classical neurotransmission occurs in the opposite direction. The DSI/DSE (depolarization-induced suppression) mechanism was described by Wilson and Nicoll in Nature in 2001 (

, 2001). The DSI (depolarization-induced suppression of inhibition) mechanism was described in 2001 and explains the rapid modulation of the neuronal network.Wilson and Nicoll, NatureDoes the endocannabinoid system exist in animals?

The ECS is present in all vertebrates and many invertebrates (except insects). The genes for CB1 and CB2 receptors have been evolutionarily conserved for over 600 million years (

, 2006). In mammals, including dogs and cats, the structure of the ECS is functionally analogous to that of humans, which explains the use of cannabinoids in veterinary medicine.McPartland et al., PMCThe endocannabinoid system is a fundamental regulatory system in mammals, connecting neurological, immunological, metabolic, and hormonal functions. Composed of CB1 and CB2 receptors, endogenous lipid ligands AEA and 2-AG, and enzymes FAAH and MAGL, the ECS plays the role of a "biological dimmer" of homeostasis. Retrograde signaling is a unique mechanism of the ECS that protects neurons from excitotoxicity and precisely modulates synapses.

Summary

The endocannabinoid system is a fundamental regulatory system in mammals, integrating neurological, immunological, metabolic, and hormonal functions. Composed of CB1 and CB2 receptors, endogenous lipid ligands AEA and 2-AG, and the enzymes FAAH and MAGL, the ECS serves as a "biological dimmer" of homeostasis. Retrograde signaling is a unique mechanism of the ECS that protects neurons from excitotoxicity and precisely modulates synapses.

Natural strategies supporting the ECS, such as physical activity, a diet rich in omega-3, cold exposure, meditation, and adequate sleep, are the foundation of a healthy endocannabinoid system tone. Conscious use of phytocannabinoids serves as a complement, not a substitute for these basic habits. Consultation with a physician is recommended before starting supplementation, especially when taking other medications.

In 2026, the ECS remains one of the most dynamically developing areas of pharmacology and physiology. Selective enzyme inhibitors, allosteric receptor modulators, and ECS pharmacogenomics open new therapeutic possibilities. Awareness of the role of the ECS in health is growing, and phytocannabinoids are becoming an increasingly well-understood tool for supporting its proper functioning.

This article is informational and educational and does not constitute medical advice. Before using cannabis, CBD, or other phytocannabinoids for therapeutic purposes, consult a physician, especially if you are taking other medications, are pregnant, or breastfeeding. Modulation of the endocannabinoid system requires an individual assessment of health status.

Endocannabinoid system (ECS) 2026: CB1/CB2 receptors, anandamide (discovered 1992), 2-AG, FAAH and MAGL enzymes, and CECD theory according to Russo.

Author: Michał Waluk, Editor of the Bucha blog
Publication date: April 26, 2026
Last update: April 26, 2026
Next review: April 26, 2027