Research Can cannabis rejuvenate our brains?

Cannabis reverses aging processes in the brain: Researchers at the University of Bonn put the memory of Methuselaus mice back to a youthful stage
The older we become, the more the ability to remember becomes less. In the course of a study, researchers from the University of Bonn and the Hebrew University in Israel succeeded in reversing the aging processes in the brain of mice. Older animals could be restored to the condition of two months young mice by prolonged low dose treatment with a cannabis drug. This opens up new options for the treatment of dementia, for example. The results will now be presented in the journal "Nature Medicine".

Like any other organ, our brain ages too. As a result, cognitive performance decreases with age. One notices this for example by the fact that it becomes harder to learn something new or to pay attention to several things at the same time. This process is normal but may also promote dementia. Researchers have long been searching for ways to slow down or even reverse this process.

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This has now been achieved by scientists from the University of Bonn and the Hebrew University of Jerusalem (Israel) in mice. These animals have only a relatively short lifetime in nature and show strong cognitive deficits already at the age of twelve months. The researchers administered a small amount of THC, the active ingredient of the hemp plant (cannabis), to mice at the age of two, twelve or 18 months over a period of four weeks..

Then they tested the learning and memory skills of the animals - including, for example, the ability to orientate and recognize fellows. Mice given only placebo showed natural age-related learning and memory loss. On the other hand, the cognitive functions of the cannabis-treated animals were as good as those of two-month-old control animals. "The treatment completely reversed the performance loss of the old animals", reported Prof. Dr. med. Andreas Zimmer from the Institute of Molecular Psychiatry at the University of Bonn, member of the Cluster of Excellence ImmunoSensation.

Years of meticulous research
This treatment success is the result of years of meticulous research. First, the scientists found that the brain ages much faster if mice do not have a functional receptor for THC. These so-called cannabinoid 1 (CB1) receptors are proteins to which substances dock and thereby trigger a signal chain. CB1 is also the cause of the intoxicating effect of THC in cannabis products, such as hashish or marijuana, that attach to the receptor. THC mimics the effects of endogenous cannabinoids that perform important functions in the brain. "With increasing age, the amount of cannabinoids naturally formed in the brain decreases," says Prof. Zimmer. "If the activity of the cannabinoid system decreases, then we find a rapid aging of the brain."

In order to find out exactly what causes the THC treatment of old mice, the researchers examined the brain tissue and the gene activity of the treated mice. The findings were surprising: the molecular signature no longer corresponded to that of old animals, but was rather similar to young animals. The number of nerve cell connections in the brain also increased again, which is an important prerequisite for learning ability. "It looked like the THC treatment had reset the molecular clock," says Zimmer.

Next step: clinical study in humans
The dosage of THC administered was chosen to be low enough to preclude any noise effect in the mice. Cannabis products are already approved as medications, for example for pain relief. In a next step, the researchers want to investigate in a clinical study whether THC can reverse the aging process of the brain in humans and increase cognitive performance.

The North Rhine-Westphalian Science Minister Svenja Schulze was enthusiastic about the study: "The promotion of knowledge-led research is irreplaceable, because it is the breeding ground for all questions in the application. Although it is a long way from mouse to human, the prospect of THC being used to treat dementia makes me extremely positive. "(Sb)

Publication: A chronic low dose of delta9-tetrahydrocannabinol (THC) restores cognitive function in old mice, Nature Medicine, DOI: 10.1038 / nm.4311