Category Archives: Endocannabinoid System

The Endocannabinoid System and Its Role in Regulating the Intrinsic Neural Circuitry of the Gastrointestinal Tract.

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“Endocannabinoids are important neuromodulators in the central nervous system.

They regulate central transmission through pre- and postsynaptic actions on neurons and indirectly through effects on glial cells.

Cannabinoids (CBs) also regulate neurotransmission in the enteric nervous system (ENS) of the gastrointestinal (GI) tract.

The ENS consists of intrinsic primary afferent neurons, interneurons, and motor neurons arranged in two ganglionated plexuses which control all the functions of the gut.

Increasing evidence suggests that endocannabinoids are potent neuromodulators in the ENS.

In this review, we will highlight key observations on the localization of CB receptors and molecules involved in the synthesis and degradation of endocannabinoids in the ENS.

We will discuss endocannabinoid signaling mechanisms, endocannabinoid tone and concepts of CB receptor metaplasticity in the ENS. We will also touch on some examples of enteric neural signaling in relation neuromuscular, secretomotor, and enteroendocrine transmission in the ENS. Finally, we will briefly discuss some key future directions.”

The Endocannabinoid Signaling System in the CNS: A Primer.

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“The purpose of this chapter is to provide an introduction to the mechanisms for the regulation of endocannabinoid signaling through CB1 cannabinoid receptors in the central nervous system.

The processes involved in the synthesis and degradation of the two most well-studied endocannabinoids, 2-arachidonoylglycerol and N-arachidonylethanolamine are outlined along with information regarding the regulation of the proteins involved.

Signaling mechanisms and pharmacology of the CB1 cannabinoid receptor are outlined, as is the paradigm of endocannabinoid/CB1 receptor regulation of neurotransmitter release.

The reader is encouraged to appreciate the importance of the endocannabinoid/CB1 receptor signaling system in the regulation of synaptic activity in the brain.”

CB1 cannabinoid receptor enrichment in the ependymal region of the adult human spinal cord

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Figure 1

“Cannabinoids are involved in the regulation of neural stem cell biology and their receptors are expressed in the neurogenic niches of adult rodents.

In the spinal cord of rats and mice, neural stem cells can be found in the ependymal region, surrounding the central canal, but there is evidence that this region is largely different in adult humans: lacks a patent canal and presents perivascular pseudorosettes, typically found in low grade ependymomas.

Using Laser Capture Microdissection, Taqman gene expression assays and immunohistochemistry, we have studied the expression of endocannabinoid system components (receptors and enzymes) at the human spinal cord ependymal region.

We observe that ependymal region is enriched in CB1 cannabinoid receptor, due to high CB1 expression in GFAP+ astrocytic domains. However, in human spinal cord levels that retain central canal patency we found ependymal cells with high CB1 expression, equivalent to the CB1HIGH cell subpopulation described in rodents.

Our results support the existence of ependymal CB1HIGH cells across species, and may encourage further studies on this subpopulation, although only in cases when central canal is patent. In the adult human ependyma, which usually shows central canal absence, CB1 may play a different role by modulating astrocyte functions.”

http://www.nature.com/articles/srep17745

Prevention of Diet-Induced Obesity Effects on Body Weight and Gut Microbiota in Mice Treated Chronically with Δ9-Tetrahydrocannabinol.

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“Acute administration of cannabinoid CB1 receptor agonists, or the ingestion of cannabis, induces short-term hyperphagia. However, the incidence of obesity is lower in frequent cannabis users compared to non-users.

Gut microbiota affects host metabolism and altered microbial profiles are observed in obese states. Gut microbiota modifies adipogenesis through actions on the endocannabinoid system. This study investigated the effect of chronic THC administration on body weight and gut microbiota in diet-induced obese (DIO) and lean mice.

THC reduced weight gain, fat mass gain and energy intake in DIO but not lean mice. DIO-induced changes in select gut microbiota were prevented in mice chronically administered THC.

Chronic THC treatment reduced energy intake and prevented high fat diet-induced increases in body weight and adiposity; effects that were unlikely to be a result of sedation or altered gastrointestinal transit. Changes in gut microbiota potentially contribute to chronic THC-induced actions on body weight in obesity.”

http://www.ncbi.nlm.nih.gov/pubmed/26633823

“Prevention of Diet-Induced Obesity Effects on Body Weight and Gut Microbiota in Mice Treated Chronically with Δ9-Tetrahydrocannabinol… To follow up on our hypothesis that exposure to THC may produce weight loss, in the current study we investigated whether chronic THC inhibits weight gain in lean and diet-induced obese (DIO) mice… We present data showing that chronic administration of the CB1/CB2 receptor partial agonist, THC, prevents weight gain in DIO mice. Furthermore, we show evidence that DIO-mediated modifications in gut microbiota are prevented in chronically THC treated mice… In conclusion, we present data showing the CB1/CB2 receptor partial agonist THC, induces hypophagia and prevents weight gain in obesity and suggest these actions may be mediated in part by modifications of the gut microbiota.”  http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144270

Anandamide-induced Ca2+ elevation leading to p38 MAPK phosphorylation and subsequent cell death via apoptosis in human osteosarcoma cells.

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“The effect of anandamide on human osteoblasts is unclear. This study examined the effect of anandamide on viability, apoptosis, mitogen-activated protein kinases (MAPKs) and Ca2+ levels in MG63 osteosarcoma cells. Anandamide at 50-200 microM decreased cell viability via apoptosis as demonstrated by propidium iodide staining and activation of caspase-3. Immunoblotting suggested that anandamide induced expression of ERK, JNK and p38 MAPK. Anandamide-induced cell death and apoptosis were reversed by SB203580, but not by PD98059 and SP600125, suggesting that anandamide’s action was via p38 MAPK, but not via ERK and JNK. Anandamide at 1-100 microM induced [Ca2+]i increases. Removal of extracellular Ca2+ decreased the anandamide response, indicating that anandamide induced Ca2+ influx and Ca2+ release. Chelation of intracellular Ca2+ with BAPTA reversed anandamide-induced cell death and p38 MAPK phosphorylation. Collectively, in MG63 cells, anandamide induced [Ca2+]i increases which evoked p38 MAPK phosphorylation. This p38 MAPK phosphorylation subsequently activated caspase-3 leading to apoptosis.”

http://www.ncbi.nlm.nih.gov/pubmed/17222495

Cannabinoid receptors and their role in neuroprotection.

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“Evidence has accumulated over the last few years suggesting that endocannabinoid-based drugs may potentially be useful to reduce the effects of neurodegeneration. In fact, exogenous and endogenous cannabinoids were shown to exert neuroprotection in a variety of in vitro and in vivo models of neuronal injury via different mechanisms,”

http://www.ncbi.nlm.nih.gov/pubmed/16052037

The endocannabinoid system as a target for the treatment of neuronal damage.

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“Cannabinoids have been proposed as clinically promising neuroprotective molecules, based on their capability to normalize glutamate homeostasis, reducing excitotoxicity, to inhibit calcium influx, lowering intracellular levels and the subsequent activation of calcium-dependent destructive pathways, and to reduce the generation of reactive oxygen intermediates or to limit their toxicity, decreasing oxidative injury.

Cannabinoids are also able to decrease local inflammatory events by acting on glial processes that regulate neuronal survival, and to restore blood supply by reducing vasocontriction produced by several endothelium-derived factors.

Treatment of neurodegenerative disorders is a challenge for neuroscientists and neurologists. Unhappily, the efficacy of available medicines is still poor and there is an urgent need for novel neuroprotective agents. Cannabinoids can serve this purpose given their recognized antiexcitotoxic, antioxidant and anti-inflammatory properties.”

http://www.ncbi.nlm.nih.gov/pubmed/20230193

The endocannabinoid system in guarding against fear, anxiety and stress.

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“The endocannabinoid (eCB) system has emerged as a central integrator linking the perception of external and internal stimuli to distinct neurophysiological and behavioural outcomes (such as fear reaction, anxiety and stress-coping), thus allowing an organism to adapt to its changing environment.

eCB signalling seems to determine the value of fear-evoking stimuli and to tune appropriate behavioural responses, which are essential for the organism’s long-term viability, homeostasis and stress resilience; and dysregulation of eCB signalling can lead to psychiatric disorders.

An understanding of the underlying neural cell populations and cellular processes enables the development of therapeutic strategies to mitigate behavioural maladaptation.”

http://www.ncbi.nlm.nih.gov/pubmed/26585799

Cannabinoids in the management of chronic pain: a front line clinical perspective.

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“Chronic pain is an escalating public health problem. Currently available treatments are inadequate to control chronic pain conditions, and there is a critical need for novel treatments.

Over a half century of elegant preclinical research has identified the presence of a sophisticated endocannabinoid system that is part of our natural pain and immune defense network.

Convergent work has supported the significant potential to exploit this system to decrease pain and inflammation.

Although the clinical research remains in its infancy, recent systematic reviews have found that 25 of 30 randomized controlled trials have demonstrated a significant analgesic effect.

The authors concluded that cannabinoids currently available for clinical use demonstrate a modest analgesic effect and are safe for the management of chronic pain.

There is a critical need for more translational research so that the excellent work of Dr. Itai Bab and our basic science colleagues around the world can move forward in providing novel cannabinoid-based medicines.

This should include more potent analgesics that are limited in side effects with several routes of delivery. Our patients deserve additional agents for pain control with a novel mechanism of action, and cannabinoids are the new frontier.”

http://www.ncbi.nlm.nih.gov/pubmed/26581068

The cannabinoid system in the retrosplenial cortex modulates fear memory consolidation, reconsolidation, and extinction.

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“Despite the fact that the cannabinoid receptor type 1 (CB1R) plays a pivotal role in emotional memory processing in different regions of the brain, its function in the retrosplenial cortex (RSC) remains unknown. Here, using contextual fear conditioning in rats, we showed that a post-training intra-RSC infusion of the CB1R antagonist AM251 impaired, and the agonist CP55940 improved, long-term memory consolidation. Additionally, a post-reactivation infusion of AM251 enhanced memory reconsolidation, while CP55940 had the opposite effect. Finally, AM251 blocked extinction, whereas CP55940 facilitated it and maintained memory extinguished over time. Altogether, our data strongly suggest that the cannabinoid system of the RSC modulates emotional memory.”

http://www.ncbi.nlm.nih.gov/pubmed/26572648