Tag Archives: cannabinoid receptors

Crucial Roles of the Endocannabinoid 2-Arachidonoylglycerol in the Suppression of Epileptic Seizures.

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“Endocannabinoid signaling is considered to suppress excessive excitability of neural circuits and to protect the brain from seizures. However, the precise mechanisms of this effect are poorly understood.

Here, we report that 2-arachidonoylglycerol (2-AG), one of the two major endocannabinoids, is crucial for suppressing seizures.

We found that kainate-induced seizures in mice lacking the 2-AG synthesizing enzyme, diacylglycerol lipase α, were much more severe compared with those in cannabinoid CB1 receptor knockout mice and were comparable to those in mice lacking both CB1– and CB2-receptor-mediated signaling.

In the dentate gyrus, 2-AG suppressed excitatory input around the inner and middle molecular layers through CB1 and presumably CB2 receptors, respectively.

This 2-AG-mediated suppression contributed to decreased granule cell excitability and the dampening of seizures. Furthermore, lack of 2-AG signaling enhanced kindling epileptogenesis and spontaneous seizures after kainate-induced status epilepticus.

These results highlight critical roles of 2-AG signaling in the suppression of epileptic seizures.”

http://www.ncbi.nlm.nih.gov/pubmed/27452464

Peripheral interactions between cannabinoid and opioid receptor agonists in a model of inflammatory mechanical hyperalgesia.

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“Activation of opioid and cannabinoid receptors expressed in nociceptors induces effective antihyperalgesia.

In this study, we examined whether combinations of opioid and cannabinoid receptor agonists directed at the injured site would enhance therapeutic effectiveness.

Our findings showed that MOR and CB1 agonists directed at the inflamed site effectively attenuate mechanical hyperalgesia when administered individually, but exert opposing effects when administered together.

The antagonistic interactions between the two classes of drugs at the inflamed site suggest distinct mechanisms unique to peripheral nociceptors or inflamed tissue, and therefore require further studies to investigate whether the therapeutic utility of the combined drug treatments in chronic pain conditions can be optimized.”

http://www.ncbi.nlm.nih.gov/pubmed/27450703

A study of cannabinoid-1 receptors during the early phase of excitotoxic damage to rat spinal locomotor networks in vitro.

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“Endocannabinoids acting on cannabinoid-1 receptors (CB1Rs) are proposed to protect brain and spinal neurons from excitotoxic damage.

The ability to recover from spinal cord injury (SCI), in which excitotoxicity is a major player, is usually investigated at late times after modulation of CB1Rs whose role in the early phases of SCI remains unclear.

Using the rat spinal cord in vitro as a model for studying SCI initial pathophysiology, we investigated if agonists or antagonists of CB1Rs might affect SCI induced by the excitotoxic agent kainate (KA) within 24 h from a transient (1 h) application of this glutamate agonist.

The present data indicate that the early phases of excitotoxic SCI could not be arrested by pharmacologically exploiting the endocannabinoid system, consistent with the notion that AEA and its derivatives are more useful to treat late SCI phases.”

http://www.ncbi.nlm.nih.gov/pubmed/27450568

Type-2 Cannabinoid Receptors in Neurodegeneration.

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“Based on its wide expression in immune cells, type 2 cannabinoid (CB2) receptors were traditionally thought to act as “peripheral receptors” with an almost exclusively immunomodulatory function. However, their recent identification in mammalian brain areas, as well as in distinct neuronal cells, has opened the way to a re-consideration of CB2 signaling in the context of brain pathophysiology, synaptic plasticity and neuroprotection. To date, accumulated evidence from several independent preclinical studies has offered new perspectives on the possible involvement of CB2signaling in brain and spinal cord traumatic injury, as well as in the most relevant neurodegenerative disorders like Alzheimer’s disease, Parkinson’s disease and Huntington’s chorea. Here, we will review available information on CB2 in these disease conditions, along with data that support also its therapeutic potential to treat them.”

http://www.ncbi.nlm.nih.gov/pubmed/27450295

Discovery of novel Tetrahydrobenzo[b]thiophene and pyrrole based scaffolds as potent and selective CB2 receptor ligands: The structural elements controlling binding affinity, selectivity and functionality.

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“CB2-based therapeutics show strong potential in the treatment of diverse diseases such as inflammation, multiple sclerosis, pain, immune-related disorders, osteoporosis and cancer, without eliciting the typical neurobehavioral side effects of CB1 ligands.

For this reason, research activities are currently directed towards the development of CB2 selective ligands. Herein, the synthesis of novel heterocyclic-based CB2 selective compounds is reported.

The present findings thus pave the way to the design and optimization of heterocyclic-based scaffolds with lipophilic carboxamide and/or retroamide substituent that can be exploited as potential CB2 receptor activity modulators.”

http://www.ncbi.nlm.nih.gov/pubmed/27448919

Cannabinoid Modulation of Cutaneous Aδ Nociceptors During Inflammation

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“Previous studies have demonstrated that locally administered cannabinoids attenuate allodynia and hyperalgesia through activation of peripheral cannabinoid receptors (CB1 and CB2).

These results suggest that attenuation of mechanically evoked responses of Aδ nociceptors contributes to the behavioral antinociception produced by activation of peripheral CB1 receptors during inflammation.

Several studies have demonstrated that locally administered cannabinoids produce antinociception in animal models of both acute and persistent pain through peripheral mechanisms.

Taken together, our data suggest that peripherally acting cannabinoids could be a potential therapeutic treatment for chronic inflammatory pain.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2585399/

 

Allosteric modulation of heterodimeric G-protein-coupled receptors.

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“G-protein-coupled receptors (GPCRs) are, and will probably remain, the most tractable class of targets for the development of small-molecule therapeutic medicines.

Currently, all approved GPCR-directed medicines are agonists or antagonists at orthosteric binding sites – except for the calcimimetic cinacalcet, which is a positive allosteric modulator of Ca(2+)-sensing receptors, and maraviroc, an allosteric inhibitor of CC-chemokine receptor (CCR) 5.

It is now widely accepted that GPCRs exist and might function as dimers, and there is growing evidence for the physiological presence and relevance of GPCR heterodimers.

Molecules that can regulate a GPCR within a heterodimer, through allosteric effects between the two protomers of the dimer or between a protomer or protomers and the associated G protein, offer the potential to function in a highly selective and tissue-specific way.

Despite the conceptual attraction of such allosteric regulators of GPCR heterodimers as drugs, they cannot be identified by screening approaches that routinely use a ‘one GPCR target at a time’ strategy.

In our opinion, this will require the development of new approaches for screening and a return to the use of physiologically relevant cell systems at an early stage in compound identification.”

http://www.ncbi.nlm.nih.gov/pubmed/18022255

Allosteric modulation of the cannabinoid CB1 receptor.

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“We investigated the pharmacology of three novel compounds, Org 27569 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)-ethyl]-amide), Org 27759 (3-ethyl-5-fluoro-1H-indole-2-carboxylic acid [2-94-dimethylamino-phenyl)-ethyl]-amide), and Org 29647 (5-chloro-3-ethyl-1H-indole-2-carboxylic acid (1-benzyl-pyrrolidin-3-yl)-amide, 2-enedioic acid salt), at the cannabinoid CB1 receptor.

These data suggest that the Org compounds bind allosterically to the CB1 receptor and elicit a conformational change that increases agonist affinity for the orthosteric binding site.

The data presented clearly demonstrate, for the first time, that the cannabinoid CB1 receptor contains an allosteric binding site that can be recognized by synthetic small molecule ligands.”

http://www.ncbi.nlm.nih.gov/pubmed/16113085

Cannabidiol is an allosteric modulator at mu- and delta-opioid receptors.

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“The mechanism of action of cannabidiol, one of the major constituents of cannabis, is not well understood but a noncompetitive interaction with mu opioid receptors has been suggested on the basis of saturation binding experiments.

The aim of the present study was to examine whether cannabidiol is an allosteric modulator at this receptor, using kinetic binding studies, which are particularly sensitive for the measurement of allosteric interactions at G protein-coupled receptors.

In addition, we studied whether such a mechanism also extends to the delta opioid receptor. For comparison, (-)-Delta9-tetrahydrocannabinol (THC; another major constituent of cannabis) and rimonabant (a cannabinoid CB1 receptor antagonist) were studied.

The present study shows that cannabidiol is an allosteric modulator at mu and delta opioid receptors. This property is shared by THC but not by rimonabant.”

http://www.ncbi.nlm.nih.gov/pubmed/16489449

Arachidonylcyclopropylamide increases microglial cell migration through cannabinoid CB2 and abnormal-cannabidiol-sensitive receptors.

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“Microglial cells, the macrophages of the brain, express low, yet detectable levels of cannabinoid CB(1) receptors, which are known to modulate cell migration.

To determine if cannabinoid CB(1) receptors expressed by microglial cells modulate their migration, we assessed whether arachidonylcyclopropylamide (ACPA, an agonist shown to selectively activate CB(1) receptors) affects the migration of BV-2 cells, a mouse microglial cell line.

Our results suggest that cannabinoid CB(2) receptors and abn-CBD receptors, rather than cannabinoid CB(1) receptors, regulate microglial cell migration, and that ACPA is a broad cannabinoid receptor agonist.”

http://www.ncbi.nlm.nih.gov/pubmed/12921861