Cannabis assists the endocannabinoid system in supporting the process of neurogenesis.
Neurogenesis (growing new brain cells), in adults, is critical to learning, mood regulation and maintaining brain health; the endocannabinoid system plays an active role in this process. Interestingly, many psychiatric disorders, like depression and schizophrenia, are accompanied by impaired neurogenesis.
The brain begins the neurogenesis process immediately following injury. It does so by increasing its proliferation of neural progenitor cells (NPCs). In this way, the brain attempts to heal the injury and prevent further damage.
What Role Does the Endocannabinoid System Play in Neurogenesis?
The endocannabinoid system is the body’s own system of cannabinoid molecules and cannabinoid receptors that are predominantly found in the brain and throughout the immune system, although these receptors are also found throughout the organs and tissues of your body. When the brain is injured, as in a stroke or force related traumatic injury, the endocannabinoid system ramps up production of endocannabinoid molecules and receptors. Scientists believe this is evidence that the endocannabinoid system is involved in neural regeneration.
As soon as brain injury occurs, there is an increase in NPCs to try to stop the damage from spreading and to start healing.
In animal studies, the participation of the endocannabinoid system in neurogenesis has been confirmed. In an animal model of brain injury, mice bred to lack cannabinoid receptor CB1 or mice with the activity of the CB1 receptor blocked, had reduced neurogenesis. In in vitro studies on neural cells, growth and division of NPCs were inhibited when the activity of the CB1 and CB2receptors were blocked
Cannabidiol (CBD) has been shown to increase neurogenesis in animals. For example, one study on an animal model of chronic stress found that CBD could undo the reduced neurogenesis and the anxiety. Animal studies have also shown that neurogenesis only occurs after long term administration of cannabinoids, so it doesn’t have an immediate effect.
CBD increases neurogenesis.
Further evidence for the role of the endocannabinoid system in neurogenesis was found by looking more closely at the brain.High levels of CB1 and CB2 receptors were found in the part of the brain that is known to be responsible for containing NPCs and promoting neuron growth and differentiation, the subventricular zone (SVZ). The two kinds of diacylglycerol lipases (DAGLs), enzymes that help synthesize the endocannabinoid 2-arachidonoylglycerol (2-AG), were also found in this part of the brain. Their presence also points to an active role of the endocannabinoid system in neurogenesis.
The mechanism seems to involve both cannabinoid receptors, CB1 and CB2. A variety of protein signalling cascades have been found to result in neural regeneration in both animals and brain cells studied in vitro. These signaling pathways, once activated by cannabinoid molecules binding to the cannabinoid receptors, first encourage NPCs to grow and divide, a process called proliferation.
After the population of NPCs has grown, they then begin to migrate to different parts of the brain and undergo a transformation into the type of brain cell that is needed. This is called differentiation, and it is also mediated by cannabinoids. After differentiation, cannabinoid receptors remain on the cells and are thought to play a part in the signalling pathways that decide whether the cell should continue to live or should undergo programmed cell death, or cell maintenance.
However, the practical use of cannabis for encouraging neural regeneration is going to be limited by the psychoactive side effects of activating the CB1 receptor by THC. Some researchers are examining other ways of manipulating the endocannabinoid system to encourage neurogenesis by administering drugs that prevent endocannabinoids from being broken down in the brain. This would increase the numbers of endocannabinoids present in the brain and exert proliferative effects while limiting any undesirable psychoactive effects.