Salon

What does marijuana do in the brain? It produces some excitatory behavioural changes, including euphoria, but it is not generally regarded as a stimulant. It can also produce some sedative effects, but not to the extent of a barbiturate or alcohol. It produces mild analgesic effects (pain relief ) as well, but this action is not related pharmacologically to the pain-relieving effects of opiates or aspirin. Finally, marijuana produces hallucinations at high doses, but its structure does not resemble LSD or any other drug formally categorized as a hallucinogen. Thus, marijuana’s effects on our body and brain are complex. Just how does it achieve these effects?

The very high potency and structure of the cannabinoids contained within the marijuana plant enable them to cross the blood-brain barrier and bind to a receptor for the brain’s very own endogenous cannabinoid neurotransmitter system. If this were not true, then the marijuana plant would be popular only for its use in making rope, paper, and cloth. The two currently identified neurotransmitter compounds (and there are probably more) in this system are anandamide, from the Sanskrit word ananda meaning “bliss,” and 2-AG (2-arachidonoyl-glycerol). Unlike the other neurotransmitters that I’ve discussed, these two “endocannabinoids” are not stored in synaptic vesicles.

Rather, they are both produced within neurons and released to flow back across the synapse to find their receptors, designated as CB1 and CB2. There are probably more of these CB receptors for marijuana in the human brain than for any other known neurotransmitter. The great abundance of these receptors and their widespread location gives an indication of the importance of the endocannabinoid system in the regulation of the brain’s normal functioning.

Let’s take a look at what these endocannabinoids do in the brain, to gain some insight into the consequences of smoking (or eating) marijuana. For example, anandamide inhibits the release of glutamate and acetylcholine within the cortex and hippocampus, an action that may underlie the ability of marijuana to impair one’s capacity to form new memories when using the drug. The presence of cannabinoid receptors in the parts of the brain that control movement may explain the stumbling behavior that some marijuana users experience. Cannabinoid receptors greatly enhance the release of dopamine; this action plays a critical role in the ability of marijuana to produce euphoria. Finally, stimulation of cannabinoid receptors in the feeding centers of the hypothalamus may underlie the classic marijuana side effect known as the “munchies.”

In contrast, stimulating the brain’s cannabinoid receptors may offer protection from the consequences of stroke, chronic pain, and neuroinflammation. Surprisingly, it may also protect against some aspects of age-associated memory loss. Ordinarily, we do not view marijuana as being good for our brain and certainly not for making memories. How could a drug that clearly impairs memory while people are under its sway protect their brains from the consequences of aging?

The answer likely has everything to do with the way that young and old brains function and the age-related changes in the actions of the neurotransmitters acetylcholine and glutamate. These two neurotransmitters are involved in making new memories and destroying old or unnecessary ones. Early in life, this process of creation and destruction is in balance, and so interfering with it-which occurs when using marijuana- might impair memory. But later in life, the roles of these neurotransmitters change in significant ways. In addition, the aged brain displays increasing evidence of inflammation and a dramatic decline in the production of new neurons, called neurogenesis. Marijuana may offer protection in at least three different ways: by preventing the damaging actions of glutamate, by reducing brain inflammation, and by restoring neurogenesis. Thus, later in life, marijuana might actually help your brain, rather than harm it. Research in my laboratory by Dr. Yannick Marchalant suggests that it takes very little marijuana to produce benefits in the older brain; his motto is “a puff is enough.”The challenge for pharmacologists in the future will be to isolate the beneficial aspects of marijuana from its psychoactive effects, which themselves can be an additional burden to those suffering from the consequences of an aging brain.

Food for thought — well, if you didn’t already have, “The Munchies…”

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Ok, seriously, read the full article. There’s some research ground being covered here that may shoot dementia dead in its tracks — along with other benefits — and fundamentally rewrite our thinking on what used to be considered a terrible, horrible, no good, very bad thing…