The human body is not a passive object that foreign substances act upon from the outside. It is an active biological system that maintains its own internal equilibrium through a continuous process of chemical signalling between cells, organs, and systems. The nervous system regulates movement, sensation, and cognition. The immune system regulates the response to infection and injury. The endocrine system regulates hormones, metabolism, and reproduction. Each of these systems was identified, named, and understood by medical science over the past two centuries, and that understanding transformed medicine. The endocannabinoid system is the most recently identified of the major regulatory systems of the human body. It was discovered in 1988. Its existence had not been suspected before the 1960s, when Raphael Mechoulam's isolation of THC gave researchers the molecular tool they needed to find it. What the endocannabinoid system does, where it operates, and why its existence makes the "unnatural drug" argument against cannabis scientifically unsustainable is the subject of this article.

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The endocannabinoid system operates through two primary receptors: CB1 and CB2. Both are G-protein coupled receptors, a class of protein structures embedded in the outer membrane of cells that receive chemical signals from outside the cell and translate them into changes in the cell's internal activity. G-protein coupled receptors are the most common type of receptor in the human body and the target of approximately 34 percent of all approved pharmaceutical drugs. The cannabinoid receptors are members of this family. They are not exotic or anomalous features of human biology. They are mainstream components of the body's standard chemical communication architecture.

The concentration of CB1 receptors in the brain stem is directly relevant to one of the most important facts about cannabis safety. The brain stem controls respiration: the automatic process of breathing that continues during sleep and unconsciousness. Opioids such as morphine and heroin bind to receptors that are densely concentrated in the brain stem's respiratory control centres, which is why opioid overdose kills through respiratory depression. The person stops breathing. CB1 receptors are present in the brain stem but are not concentrated in the respiratory control centres. This is why cannabis cannot cause fatal respiratory depression, regardless of dose. It is not a matter of cannabis being a weaker drug. It is a matter of receptor distribution. The plant interacts with a system that is not located in the part of the brain that controls breathing. This is why the zero-death-from-overdose record has held across five thousand years of documented use and will continue to hold. The biology does not permit a fatal overdose in the way opioids permit it.

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The CB1 and CB2 receptors exist because the body produces its own molecules to activate them. These molecules are the endocannabinoids: cannabis-like compounds produced internally by the human body. Two have been most thoroughly studied. The first is anandamide, isolated by Mechoulam and Devane in 1992 and named from the Sanskrit word for bliss. The second is 2-arachidonoylglycerol, known as 2-AG, isolated by Mechoulam's group in 1995.

Both anandamide and 2-AG are lipid-based neurotransmitters: they are made from fatty acids in the cell membrane rather than from amino acids like most classical neurotransmitters. This means they cannot be stored in vesicles and released on demand the way dopamine or serotonin are stored and released. Instead, they are synthesised on demand, at the precise moment and location where they are needed, released, bind to the receptor, perform their function, and are then rapidly broken down by specific enzymes. Anandamide is broken down by an enzyme called FAAH (fatty acid amide hydrolase). 2-AG is broken down by MAGL (monoacylglycerol lipase). This rapid synthesis-and-degradation cycle means the endocannabinoid system operates with great precision: its signals are local, immediate, and self-terminating.

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The most important and most distinctive feature of how endocannabinoids work is their direction of travel. Most neurotransmitters are released by the presynaptic neuron (the sending cell) and travel forward across the synapse to bind to receptors on the postsynaptic neuron (the receiving cell). This is the standard direction of neural communication: signal travels from sender to receiver. Endocannabinoids do the opposite. They are released by the postsynaptic neuron and travel backward across the synapse to bind to receptors on the presynaptic neuron. This is called retrograde signalling, and it is the mechanism through which the endocannabinoid system performs its primary regulatory function.

The significance of this retrograde direction becomes clear when you understand what happens at the synapse that the postsynaptic neuron is responding to. When a neuron is being over-stimulated, receiving too many signals, running too hot, the postsynaptic neuron produces endocannabinoids and sends them backward to the presynaptic neuron. The endocannabinoids bind to the CB1 receptor on the presynaptic neuron and reduce the amount of neurotransmitter being released. The over-excited neuron is told, by the receiving cell, to calm down. The signal is modulated. The system returns to balance.

This retrograde modulation operates on two of the brain's most important neurotransmitters: glutamate and GABA. Glutamate is the brain's primary excitatory neurotransmitter. It accelerates neural activity. It is essential for learning, memory formation, and alertness. But excessive glutamate activity is damaging and in extreme cases fatal: it is the mechanism through which stroke causes brain damage, and the mechanism that produces epileptic seizures. GABA is the brain's primary inhibitory neurotransmitter. It calms neural activity, reduces anxiety, promotes sleep, and moderates the stress response. Endocannabinoids, through retrograde signalling, modulate the release of both glutamate and GABA at synapses throughout the brain, fine-tuning the balance between excitation and inhibition that governs virtually every aspect of neurological function.

This is why cannabis is effective in treating epilepsy: it reduces excessive glutamate-driven seizure activity. This is why it is studied in PTSD: it modulates the amygdala's over-activated fear response by reducing glutamate excitation in the fear circuit. This is why it reduces anxiety: it enhances GABA-mediated inhibition in the circuits associated with the stress response. These are not speculative mechanisms. They are documented in peer-reviewed literature and, in the case of epilepsy, validated by regulatory approval. The FDA approved Epidiolex (purified CBD) in 2018 for two rare and severe forms of childhood epilepsy. The European Medicines Agency followed. The pharmacological mechanism is the endocannabinoid system. The retrograde modulation that El Guindy described in 1925 as "furious delirium" is, in therapeutic doses and in therapeutic contexts, the reduction of seizures in children.

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The overarching function of the endocannabinoid system is homeostasis: the maintenance of the body's internal equilibrium across multiple physiological parameters. Mechoulam described this in his 2013 Annual Review of Psychology paper with his colleague Linda Parker, writing that the endocannabinoid system serves as a "universal regulator" of the body's response to physiological and psychological stress. The system does not have a single function. It has a coordinating function: it moderates the activity of other systems, pulling them back toward equilibrium when they deviate too far in either direction.

The specific physiological processes regulated by the endocannabinoid system include pain perception and modulation, appetite and metabolic regulation, memory formation and extinction, immune response and inflammation, stress response and emotional regulation, sleep architecture, nausea and vomiting, eye pressure, and reproductive function. This is not a peripheral list. These are central functions of daily human life. The endocannabinoid system is not the system that governs one obscure process in one organ. It is a regulatory system that touches virtually every major aspect of human physiology.

The relevance to Mauritius is direct. One in five Mauritians has type 2 diabetes, a condition associated with chronic pain (diabetic neuropathy) and metabolic dysregulation. The endocannabinoid system is involved in both pain modulation, through CB1 receptors in the spinal cord and peripheral nervous system, and metabolic regulation, through CB1 and CB2 receptors in fat tissue, the liver, and the pancreas. THCV, a minor cannabinoid in the cannabis plant, has been studied specifically for its role in insulin sensitivity and pancreatic function. The Dangerous Drugs Act 2000 classifies as a criminal offence the external activation of the biological system that is directly relevant to the most prevalent chronic disease in the country it governs.

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The endocannabinoid system makes one argument with the force of biological fact rather than political opinion. The human body did not evolve a system for interacting with a foreign intoxicant. It evolved a system for regulating its own internal chemistry, and that system uses molecules whose structure and function are closely replicated by compounds in the cannabis plant. The relationship between the cannabis plant and the endocannabinoid system is not the relationship between a dangerous external substance and a vulnerable organism. It is the relationship between a plant and a biological system that developed in parallel over hundreds of millions of years.

When someone says cannabis is an "unnatural" substance, the endocannabinoid system is the rebuttal. The body produces anandamide. Anandamide binds to the same receptor that THC binds to. The difference between anandamide and THC is a matter of molecular structure and half-life: anandamide is broken down rapidly by the FAAH enzyme; THC is not broken down as quickly and therefore produces a more sustained effect. But the receptor they activate, the biological pathway they engage, and the homeostatic function they serve are the same. When cannabis is consumed, it does not introduce an alien chemical process into the body. It amplifies and extends a process the body was already performing with its own molecules.

The Dangerous Drugs Act 2000 criminalises this amplification. It does so without having engaged, in any documented parliamentary deliberation, with the question of the endocannabinoid system. The system had been known to science for twelve years when the Act was passed. The Act treats cannabis as a substance with no relationship to the human body's normal biological function. The science has known for thirty-eight years that this description is incorrect. The law has not caught up with the biology. In Mauritius, as in every jurisdiction where cannabis remains a criminal offence, citizens are being prosecuted for stimulating a biological system that their own bodies were designed to use.

This is the fifth article in The Colonised Plant: The Cannabis Edition, June 2026, and the second in Chapter Two: The Science. The next article examines the full chemical profile of the cannabis plant: THC, CBD, and the more than 100 cannabinoids, including THCV and its specific relevance to the diabetic neuropathy epidemic in Mauritius. The complete edition is published at themeridian.info/june-2026.