Effect of cannabis: How do the psychoactive properties work?
How is it that a plant that emerged on what is now the Tibetan Plateau can change the perception of reality by humans? The secret lies in a class of compounds called cannabinoids. While cannabis plants are known to produce at least 140 types of cannabinoids, there is one that is largely responsible for many of the high sensation effects. This is tetrahydrocannabinol, or THC.
Have you ever looked at your hands? but really looked at your hands? You might think so, but people who are under the influence of cannabis may perceive mundane objects to be far more fascinating than usual.
When a person smokes or inhales cannabis, THC "goes into your lungs and is absorbed into the blood," according to Daniele Piomelli, professor of anatomy and neurobiology, biological chemistry and pharmacology at the School of Medicine. 'Irvine from the University of California. Food takes a little longer to pass through the liver, where enzymes turn the THC into a different compound that takes a little longer to have an effect on how people perceive reality.
The THC that is inhaled "reaches quite high levels quite quickly," Piomelli told Live Science. Within 20 minutes, the circulatory system transports THC molecules to all tissues in the body, including the brain, where it can alter neural chemistry.
"From the lungs, it's a pretty direct hit to the brain," said Kelly Drew, professor of chemistry and biochemistry at the University of Alaska Fairbanks.
THC molecules that cross the blood-brain barrier integrate seamlessly with receptors that usually receive compounds called endocannabinoids, which the body produces on its own. These receptors are part of the endocannabinoid system, which is involved in several functions, including stress, diet, metabolism and pain, according to Piomelli, who also heads the University of Cannabis Center for Study. Irvine.
The neuron at the receptor end of the synapse is called the postsynaptic neuron, and he "decides whether to shoot based on the input he receives," Drew (professor of chemistry and biochemistry at the University of Alaska at Fairbanks) told Live Science. These neural signals are cascaded through complex circuits of neural connections that operate on a huge scale; there are about 85 billion neurons in the brain and up to 100 trillion connections between them.
Le presynaptic neuron sends neurotransmitters through the synapse to the postsynaptic neuron, Piomelli said. But the presynaptic neuron can also receive information. When a postsynaptic neuron has fired, it can send a message through the synapse that says, "The neuron I came from has been activated," stop sending neurotransmitters, Piomelli said. It sends this "stop" message in the form of endocannabinoids that bind to a receptor called cannabinoid 1 (CB1).
"Like a blacksmith's hammer"
When THC enters the brain, the molecules diffuse into synapses where they “activate CB1 receptors,” Drew said. THC does not elicit the most extreme response possible like some synthetic cannabinoids such as K2 or the spice, but it “turns up the volume” and increases the likelihood that the presynaptic neuron it affects will temporarily stop sending neurotransmitters. , did she say.
“The high is a very simple phenomenon,” said Ms. Piomelli. “THC comes in like a mass,” flooding the endocannabinoid system with signals that postsynaptic neurons haven't sent. When presynaptic neurons in the brain are notified to stop sending neurotransmitters, it changes the normal flow of information between neurons and results in a high.
Scientists have yet to decipher exactly what is going on during this euphoria, however.
Part of the reason is that US legal restrictions make it difficult to study cannabis. But from what researchers have gathered so far, THC appears to temporarily “unplug” the network in default mode. It is the brain network that allows us to dream and think about the past and the future. When our brain is focused on a specific task, we put that network on the back burner to let our executive function take control.
THC has been shown to have a significant effect on the neural network, but researchers are not sure exactly how this happens. There are cannabinoid receptors all over the brain, including "the areas that are key nodes in the [default mode network]," Piomelli said. It is possible that THC "turns off the [network in default mode] by combining with these receptors", but it is also possible that THC stops the network by an "indirect effect that involves the cannabinoid receptors in others. regions of the brain ”.
Scientists are still working to find the mechanisms that make a person feel high, but there is reason to believe that this effect on the network in default mode is an important piece of the puzzle.
Disconnecting the network in default mode “brings us into a mental state where the function of the things we experience is less important than the things themselves: our hands are no longer just something we use to touch or grab, but something. something that has an inner existence and intrinsic value, ”said Mr. Piomelli. Psychedelics, like LSD or dried mushrooms containing psilocybin, do the same.
However, people can experience highs in different ways. The feeling of being fascinated and 'connected' to ordinary things, to things that we see and consume every day, is not universal but occurs, especially when high doses of cannabis containing THC are used ” , said Mr. Piomelli.
THC doesn't just affect the network in default mode. It can also, in the short term, flood the brain with dopamine, the brain's reward signal, according to a 2017 study published in the journal Nature. (In the long term, it may lessen the effects of dopamine, the study found.) This may partly explain the euphoria associated with high consumption and put cannabis alongside other drugs that people use. to feel pleasure.
“Any drug that has rewarding properties affects this system,” Drew said.
The effects of a “high” produced by smoked or inhaled cannabis usually last a few hours, although it takes almost as long for the effects to start to be felt. And if cannabis is not the dangerous substance attributed to it in the twentieth century, its consumption carries certain risks. On the one hand, while cannabis is legal for recreational and medical use in some states, it is still illegal in many parts of the country.
It is also important to keep in mind that cannabis is a potent pharmacological substance. Cannabis can cross the placenta, which is why pregnant women should avoid it. And "heavy drinking during adolescence can be problematic," Piomelli said. For example, cannabis - and especially synthetic cannabinoids like spices - can exacerbate psychosis. “People at risk should not smoke it,” said Drew.
Finally, cannabis affects the ability to drive, especially among occasional users. Mr Drew warned that people should not drive for three hours after smoking.
The THC will eventually leave the brain; the profusion of blood that has brought the THC to the brain will carry it to the liver, where it will be destroyed and expelled in the urine. And you won't believe it, but your hands were the same all the time.