Cannabis on the brain

Psychoactive drugs

A psychoactive drug is a chemical substance that alters brain functions and leads to a change in perception, moods, consciousness and behaviors. Psychoactive drugs lead often to dependency. When the molecules of these substances enter the body, they are called exogenous because they are not produced by the organism.

All psychoactive drugs act on the brain, especially at the synapse level that modifies the transmission of the nervous message.

These substances can act in three different ways on the synapse :

  • They can increase the production of an endogenous neurotransmitter ;

  • Stop the passage of an endogenous neurotransmitter ;

  • And, when their molecule structure is similar to an endogenous one, bind on its specific receptor instead of it.

 

Cannabis, as a psychoactive drug, acts on the brain that makes a lot of effects in the organism. The principal active component of cannabis is tetra9-hydro-cannabinol (THC) : a cannabinoid (specific molecule to cannabis) isolated by Raphael Mechoulam and Yechiel Gaoni in 1964. Cannabis effects are principally due to THC.

In the brain, there is a system called the « endocannabinoid system ». It is composed of two cannabinoid receptors : the CB1 and CB2. The activation of these receptors alters the nervous message and so behaviors, memory, pain, emotions etc. It is important to know that the number of cannabinoid receptors in the organism is really more numerous than any other classical receptor.
The endogenous molecule that binds to these receptors is anandamide. It was discovered by Mechoulam in 1992 but its role and effects are not totaly known yet.

However, THC molecule is nearly similar to anandamide one. Thus, THC is able to bind on anandamide specific receptors (cannabinoids receptors) and in this way, to activate them.

 

Difference between anandamide and THC effects

Even if anandamide role and effects are not absolutely understood yet, a lot of differences can be established between effects caused by cannabis and effects caused by anandamide. Indeed, anandamide secretion takes place in a small and specific part of the brain and in a little quantity. So, there are only certain functions of the brain which would be changed and in a weakly way. Whereas when THC is released, it acts on all cannabinoids receptors in the brain and in a big quantity. Thus, all the endocannabinoid system istimulated in the same time that creates much more effects than anandamide do. Moreover, anadamide is quickly eliminated contrary to THC, that differentiates their effects on the body. 


How it alters the nervous message

As we said, cannabis effects are due to the activation of endocannabinoid receptors. The activation of these receptors provokes modifications in the post-synaptic neuron, which leads to the braking of the neurotransmitters released and therefore induces the modification of the nerve impulse transmission in the nervous system.

Action of THC

First, THC binds on the receptors CB1. Then, these receptors modifies the activity of many intracellular enzymes : it principally reduces the activity of AMPc (which is an intracellular messenger) which leads to reduce the release of neurotransmitters in the synapse.
The transmission of the nervous message is therefore reduced or even suppressed. This process acts on all kinds of neurotransmitters but one : dopamine which plays a role in euphoria sensation.

Indeed, the euphoric effets of cannabis are due to an increase of dopamine in a certain part of the brain : the Reward System.


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