Marijuana might cause new cell growth in the brain, reads the headline, but the reality is that a synthetic cannabinoid (HU210) increases neurogenesis in the hippocampus in rats:
In mammals, new nerve cells are constantly being produced in a part of the brain called the hippocampus, which is associated with learning, memory, anxiety and depression. Other recreational drugs, such as alcohol, nicotine and cocaine, have been shown to suppress this new growth. Xia Zhang of the University of Saskatchewan in Saskatoon, Canada, and colleagues decided to see what effects a synthetic cannabinoid called HU210 had on rats’ brains.They found that giving rats high doses of HU210 twice a day for 10 days increased the rate of nerve cell formation, or neurogenesis, in the hippocampus by about 40%.
A previous study showed that the antidepressant fluoxetine (Prozac) also increases new cell growth, and the results indicated that it was this cell growth that caused Prozac’s anti-anxiety effect. Zhang wondered whether this was also the case for the cannabinoid, and so he tested the rats for behavioural changes.
When the rats who had received the cannabinoid were placed under stress, they showed fewer signs of anxiety and depression than rats who had not had the treatment. When neurogenesis was halted in these rats using X-rays, this effect disappeared, indicating that the new cell growth might be responsible for the behavioural changes.
In another study, Barry Jacobs, a neuroscientist at Princeton University, gave mice the natural cannabinoid found in marijuana, THC (D9-tetrahydrocannabinol). But he says he detected no neurogenesis, no matter what dose he gave or the length of time he gave it for.