Marijuana plants are seen in a MedReleaf facility..
(photo credit: ALEXANDER REPETSKI)
Giving rats synthetic cannabinoids soon after a traumatic event can prevent post-traumatic stress disorder-like symptoms caused by the trauma and by reminders of it.
This was discovered by Nachshon Korem and Dr. Irit Akirav of the University of Haifa’s psychology department, as just published in the journal Neuropsychopharmacology.
“The importance of this study is that it contributes to the understanding of the brain basis of the positive effect cannabis has on PTSD. This thus supports the necessity of performing human trials to examine potential ways to prevent the development of PTSD and anxiety disorders in response to a traumatic event,” the researchers said.
About 9 percent of the population suffer from PTSD; in some groups, such as Holocaust survivors, combat soldiers, prisoners, victims of assault and citizens in lines of confrontation, the prevalence is even higher.
A common phenomenon among those who suffer from trauma is that exposure to a “trauma reminder” – an event that is not essentially traumatic but evokes the memory of the experience of the traumatic event – can further heighten the negative effects of the trauma.
For example, for a person who has developed PTSD syndrome as a result of Color Red rocket-warning sirens, a trauma reminder can occur following a loud car alarm.
In previous studies by Akirav, she discovered that the use of cannabinoids within a specific time window after the traumatic event occurred reduces PTSD symptoms in rats. In this study, together with doctoral student Korem, she aimed to examine whether the use of cannabinoids may also moderate the effects of trauma in cases of exposure to trauma reminders. The researchers chose rats because of their great physiological similarity to humans in the way they respond to stressful and traumatic events.
During the first half of the experiment, the rats underwent the traumatic event of getting an electric shock and were exposed to trauma reminders on the third and fifth days of the trial.
After the event, and within the time window found in earlier studies, some of the rats were injected with a cannabinoid substance. The rats then went through extinction procedures for trauma (a conditional psychological procedure similar to exposure therapy in humans, the purpose of which is to cope with PTSD symptoms).
It became clear that the rats that were injected with the cannabinoid substance showed no PTSD symptoms such as impaired extinction learning, increased startle response, changes in sensitivity to pain and impaired plasticity in the brain’s reward center (the nucleus accumbens), compared to those not injected with the drug. The researchers added that the rats injected with the cannabinoid substance showed better results compared to rats who received the antidepressant drug sertraline, a substance used with limited success in reducing PTSD symptoms.
In fact, for some of the symptoms, the rats that were injected with the cannabinoid substance showed behavior similar to that of rats exposed to trauma but not exposed to trauma reminders.
In other words, cannabis made the effects of trauma reminders “disappear.”
Once they found the moderating effect of cannabis on behavioral aspects, the study examined the neurobiological basis for the improvement caused by the drug.
It was found that rats exposed to trauma and trauma reminders showed an increase in the expression of two receptors in the brain associated with emotional processing – the CB1 receptor, a receptor in the brain that cannabinoids bind with, and receptor GR, which is associated with exposure to stress.
On the other hand, in rats that received cannabinoids, the increase in the expression of these two receptors was prevented in the hippocampus and prefrontal cortex – areas involved in forming and saving traumatic memories.
“The findings of our study suggest that the connectivity within the brain’s fear circuit changes following trauma, and the administration of cannabinoids prevents this change from happening.
This study can lead to future trials in humans regarding possible ways to prevent the development of PTSD and anxiety disorders in response to a traumatic event,” the researchers concluded.