A Medical Look at How Our Brains Process Cannabis

Euphoria, enhanced sensation, increased appetite, and occasionally paranoia. These are the common physical effects of cannabis use. But do you know how cannabis affects our brains to produce these effects?

The cannabis plant contains at least 483 different chemical compounds. At least 100 of these compounds are cannabinoids, such as delta-9-tetrahydrocannibinol (THC), the main psychoactive ingredient in cannabis. These compounds act on the endocannabinoid system, which consists of receptors that are distributed throughout the brain and body. Receptors are proteins that can be localized to the surface of a cell and bind specific compounds, or ligands, that are found outside the cell. When the ligand binds to the receptor, this triggers a pathway inside the cell to affect cell function.

In the endocannabinoid system, there are two primary types of receptors: cannabinoid receptor type 1 (CB1) and cannabinoid receptor type 2 (CB2). These receptors can bind a number of  ligands, including endocannabinoids, which are naturally produced in the body, and external cannabinoids such as THC. In the brain, CB1 receptors are predominant and mediate the psychoactive effects of cannabinoids. CB1 receptors are found at the terminals of neurons and play an important role in the communication between neurons by mediating neurotransmitter release. Upon the binding of cannabinoids, the receptors inhibit the release of neurotransmitters from the neuron, thereby altering the signals that are sent between neurons.

CB1 receptors are enriched in many brain regions, including the cerebellum, hippocampus, hypothalamus, and amygdala, which are areas that regulate important functions such as movement, memory, appetite, and emotion, respectively. Therefore, activation of CB1 receptors by THC can alter the neural activity of these areas to affect their function. For example, CB1 receptors are present in the reward pathway of the brain, which is regulated by the neurotransmitter dopamine. Activation of CB1 receptors affects dopamine release and production in this pathway, which is likely the cause of the positive, euphoric feelings associated with cannabis use.

The role of CB2 receptors in the brain is still somewhat of a mystery. Originally, it was thought that CB2 receptors were not present in the brain. However, recent studies suggest that these receptors are present at low levels and might mediate the effects of cannabinoids through the reward pathway. More importantly, CB2 receptors are found primarily in systems outside the brain, such as the gastrointestinal tract, immune system, liver, and muscle. The ubiquitous expression of cannabinoid receptors throughout the body means that cannabis use may affect these systems and have more of an impact on overall health.

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