Cannabinoids impair working memory through astroglial CB1 receptor modulation of hippocampal LTD (Han, 2012):
The hippocampus is an area of the brain that contains a high concentration of cannabinoid receptors and is involved in the formation of memories. Long-term depression (LTD) is a form of synaptic plasticity (cell signaling between neurons) that involves persistent weak synaptic stimulation that ultimately leads to decreased efficacy at a synaptic connection by decreasing a cell’s likelihood of firing. Conversely, Long-term Potentiation (LTP) is a form of synaptic plasticity that increases the likelihood of a cell to fire.
Both LTP and LTD are processes that contribute to memory formation and LTD specifically is altered by the activation of Cannabinoid Type 1 Receptors (CB1Rs) in the hippocampus. In this study researchers studied the connections between CA1 and CA3 regions of the hippocampus to determine what cell type was causing this difference.
To study these connections, researchers selectively blockaded CB1R’s in specific subtypes of neurons. In this case they blocked CB1R’s on glutaminergic neurons, GABAergic neurons, and non-neuronal cells called astrocytes. By selectively blocking each type in mice and subsequently observing their performance in a memory test researchers were able to determine the subtype of brain cell that caused this deficit in memory.
In summary: “We conclude that the impairment of working memory by marijuana and cannabinoids is due to the activation of astroglial CB1R and is associated with astroglia-dependent hippocampal LTD in vivo.”
To watch a video of researchers explaining the studies findings check out this link:
Acetaminophen, also known as Tylenol, is one of the most commonly used non-steroidal anti-inflammatory drugs (NSAIDs) for pain relief. But did you know that its compound’s pain fighting activity arises partially through its activity on the endocannabinoid system?
The acidic cannabinoids (THCA and CBDA) along with non-acidic CBD exhibit anti-inflammatory properties by inhibiting enzymes called cyclooxygenases (COX’s). These enzymes are responsible for the production of pro-inflammatory factors called prostaglandins. This same inhibition occurs when an NSAID is taken.
Isn’t it ironic that cannabis, a compound that is significantly less toxic and harsh on the liver is illegal yet it acts on the same pathways as a commercial pain reliever? Here’s how it works:
The Prostaglandin Synthesis Pathway:
Prostaglandins are synthesized from arachidonic acid. This compound is also the precursor for the synthesis of endogenous cannabinoids.
When acetaminophen is metabolized it results in a compound p-aminophenol that is conjugated to arachidonic acid to form N-Arachidonylphenolamine (also known as AM-404).
This compound is a CB1 receptor agonist and is partially responsible for the anti-inflammatory and analgesic effects of Tylenol.
The Endocannabinoid System in Stress-Related Psychiatric Illness
What is the endocannabinoid system (ECS)?
For centuries cannabis has been used for relief from stress and anxiety suggesting that the compounds found in the plant regulate the body’s stress response, and in fact that’s just what researchers are finding. The endocannabinoid system (ECS) is a system of receptors and molecules that regulate a variety of responses in our bodies. These cannabinoid receptors coined CB1 and CB2 are like special locks only allowing the binding of molecules with specific configurations called endocannabinoids (eCBs). Cannabinoids produced in the cannabis plant can also bind to these receptors, producing a similar, but longer-lived effect than eCBs. The binding of these compounds to these receptors induces eCB signaling which serves as a means to buffer the body’s stress response.
How does the endocannabinoid system work?
Following exposure to stressful environments eCBs are released into the synapse, the space between two neuronal connections. Here they bind to cannabinoid receptors, causing the release of neurotransmitters to be inhibited in that particular neuron (presynaptic neuron).
The ECS could be compared to your brain’s climate control. When too much activity is occurring in the brain your ECS kicks in and quiets this activity, bringing levels back to base line. This eCB signaling occurs in a retrograde (backwards) fashion meaning the eCB is released from the post-synaptic neuron and acts on the cannabinoid receptors of the pre-synaptic neuron. Ultimately, this leads to an overall decrease in neurotransmitter release, quieting this activity.
The ECS and its relationship to depression and anxiety
The action of eCBs at cannabinoid receptors has been implicated in variety of mood and stress related illnesses such as depression and PTSD. To study how these receptors play a role in these disorders researchers created mice lacking the cannabinoid receptor CB1. These mice exhibit increased anxiety suggesting that these receptors are important for regulating these behaviors. Additional support for this idea came from the observation that increased levels of eCBs in blood is associated with reduced anxiety and depression while lowered levels have the opposite effect. Based on studies of these mice and the observation that cannabis alleviates stress, researchers believed that cannabinoid receptors could be an ideal target for the treatment of PTSD. They found that when they stimulated these receptors in models of PTSD using compounds similar to THC there was a significant improvement in symptoms, confirming their hunch.
Further confirmation of the involvement of cannabinoid receptors in depression and anxiety came about because of a weight loss drug that came to market in 2006 called Rimonabant. Rimonabant acts by blocking the CB1 receptor causing a significant reduction in eCB signaling. Though the drug worked well for weight loss it was promptly removed from the market after it resulted in numerous reports of severe anxiety, depression, and in some cases suicide.
Taken together, this data shows that the ECS plays a critical role in the regulation the body’s stress response with deficient eCB levels being associated with anxiety behaviors and depression, while elevated levels of eCBs are associated with reduced anxiety and stress. Through this deeper understanding of the ECS researchers can now focus on developing new compounds that act on this system to alleviate and hopefully cure some of these debilitating ailments.
Source: Hill, 2013. "Translational evidence for the involvement of the endocannabinoid system in stress-related psychiatric illnesses" Biol Mood Anxiety Disord. 2013; 3: 19.