Medical marijuana is known to ease pain in cancer patients of all ages and is used for that purpose in Israel and many other countries. Now University of Haifa researchers, working with rodents, have found that administering cannabis after a traumatic experience prevents the development of post-traumatic stress symptoms in a rat model.

They discovered that while the drug does not erase the traumatic experience, it does prevent the development of post-trauma symptoms. If clinical studies show that cannabinoids accomplish the same in humans, they could be boon to Israel, where wars, terror attacks, road accidents and other traumatic events have often occurred, as well as to the rest of the world.

Dr. Irit Akirav of the of the university’s psychology department and colleagues published her findings in the journal Neuropsychopharmacology.

“We found that there is a ‘window of opportunity’ during which administering synthetic marijuana helps deal with symptoms simulating post-traumatic stress disorder [PTSD] in rats,” said Akirav, who led the study. In the study, which she conducted with research student Eti Ganon-Elazar, the researchers set out to examine how administering cannabinoids (synthetic marijuana) affects the development of PTSD-like symptoms in rats, whose physiological reactions to traumatic and stressful events are 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 human PTSD, such as an enhanced startle reflex, impaired extinction learning and disruption of the negative feedback cycle of the stress-influenced HPA axis.

The rats were then divided into four groups. Some were given no marijuana at all; the second group were given a marijuana injection two hours after being exposed to a traumatic event; the third group after 24 hours; and the fourth group after 48 hours.

A week later, the researchers examined the rats and found that the group that had not been given marijuana and the group that got the injection 48 hours after experiencing trauma continued to display PTSD symptoms as well as a high level of anxiety.

By contrast, PTSD symptoms disappeared in the rats that were given marijuana two or 24 hours after experiencing 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 Akirav, who added that the results suggest there is a particular window of time during which administering marijuana is effective.

Because the human life span is significantly longer than that of rats, the Haifa psychologist explained, one could assume that this window of time would be longer for humans.

The second stage of the study sought to understand the brain mechanism that is put into operation during the administering of marijuana. To do this, they repeated stage one of the experiment, but after the trauma they injected the synthetic marijuana directly into the amygdala area of the brain that is known to be responsible for trauma response. The researchers found that the marijuana blocked development of PTSD symptoms in these cases as well.

From this the researchers were able to conclude that the effect of the marijuana is mediated by a CB1 receptor in the amygdala.

HU LIFE SCIENCES SEMINAR BROUGHT THE BEST Prof. Roger Kornberg of Stanford University, who was awarded the Nobel Prize in Chemistry in 2006, spent five days in Jerusalem recently to direct a “School for Life Sciences” at the Hebrew University of Jerusalem’s Institute for Advanced Studies' School for Life Sciences that focused on cancer research.

Increased understanding the molecular basis of cancer diseases has significantly improved the ability of doctors to treat certain types of the disease and prolong the life of patients – but many aspects of cancer still remain a mystery. Data gathered by the the Central Bureau of Statistics in Jerusalem indicate that cancer is now the number-one killer in Israel; heart disease used to top the list.

The “school” presented various achievements in cancer research, numerous research challenges, innovative treatment approaches and advanced developments in cancer medication. The classes explained the differences among various types of cancer – why some can be treated, while in others the research is just beginning – and why some types of cancer are more complex than others.

The event has taken place for the past 19 years.

Kornberg, who says the event leads to the sharing of knowledge and can lead to future cooperation, annually comes to HU as a guest professor at the faculty of sciences and as an associate of the biological chemistry department. The 200 participants, most of them Israeli masters and doctoral students, heard more than two dozen lectures by leading cancer researchers from here and abroad.

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