The administration of marijuana cannabinoids after experiencing a traumatic event blocks the development of post-traumatic stress disorder (PTSD)-like symptoms in rats, according to a new study published in the medical journal Neuropsychopharmacology.
“We found that there is a ‘window of opportunity’ during which administering synthetic marijuana helps deal with symptoms simulating PTSD in rats,” said Dr. Irit Akirav of the University of Haifa
‘s Department of Psychology, which led the study.
In the study, conducted by Dr. Akirav with research student Eti Ganon-Elazar, the researchers set out to investigate how cannabinoids affect the development of PTSD-like symptoms jun rats, whose physiological reactions to traumatic and stressful events is similar to human reactions.
In the first part of the study, the researchers exposed a group of rats to extreme stress, and observed that the rats did indeed display symptoms resembling PTSD in humans, such as enhanced startle reflex, impaired extinction learning, and disruption of the negative feedback cycle.
|Dr. Irit Akirav: “[Marijuana] specifically prevented the development of post-trauma symptoms”
The rats were then divided into four groups. One was given no marijuana at all; the second was given a marijuana injection two hours after being exposed to a traumatic event; the third group was given marijuana after 24 hours, and the fourth group after 48 hours.
A week later, researchers examined the rats and found that the group which had been given no marijuana, as well as the group that got the injection 48 hours after experiencing trauma, continued to display PTSD symptoms as well as a high level of anxiety.
But the PTSD symptoms disappeared in the rats that were given marijuana 2 or 24 hours after trauma, even though these rats had also developed a high level of anxiety.
“This indicates that the marijuana did not erase the experience of the trauma, but that it specifically prevented the development of post-trauma symptoms in the rat model,” said Dr. Akirav, who said the results suggest a particular window of time during which marijuana is effective against PTSD.
Because the human lifespan is significantly longer than that of rats, Dr. Akirva said, one could assume that this window of opportunity would be longer for humans.
The second stage of the study sought to understand the brain mechanism put into operation during the administration of marijuana. To do this, researchers repeated stage one of the experiment, but after the trauma they injected the synthetic cannabinoids directly into the amygdala area of the brain, the area known to be responsible for response to trauma.
The researchers found that the cannabinoids blocked development of PTSD symptoms in those cases as well. From this the researchers were able to conclude that the effects of marijuana on PTSD is mediated by a CB1 receptor in the amygdala.
Dr. Akirav is confident that psychiatrists will take her research forward to implement on humans, reports AFP