Cannabinoid receptor 1

Last updated

CNR1
Human cannabinoid receptor 1 (CB1) PDB 5XRA.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases CNR1 , CANN6, CB-R, CB1, CB1A, CB1K5, CB1R, CNR, cannabinoid receptor 1 (brain), cannabinoid receptor 1, cannabinoid CB1 receptor gene
External IDs OMIM: 114610; MGI: 104615; HomoloGene: 7273; GeneCards: CNR1; OMA:CNR1 - orthologs
Orthologs
SpeciesHumanMouse
Entrez

1268

12801

Ensembl

ENSG00000118432

ENSMUSG00000044288

UniProt

P21554

P47746

RefSeq (mRNA)

NM_007726
NM_001355020
NM_001355021
NM_001365881

RefSeq (protein)

NP_031752
NP_001341949
NP_001341950
NP_001352810

Location (UCSC) Chr 6: 88.14 – 88.17 Mb Chr 4: 33.92 – 33.95 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Cannabinoid receptor 1 (CB1), is a G protein-coupled cannabinoid receptor that in humans is encoded by the CNR1 gene. [5] And discovered, by determination and characterization in 1988, [6] and cloned in 1990 for the first time. [7] [8] [9] The human CB1 receptor is expressed in the peripheral nervous system and central nervous system. [5] It is activated by endogenous cannabinoids [10] called endocannabinoids, a group of retrograde neurotransmitters that include lipids, such as anandamide and 2-arachidonoylglycerol; plant phytocannabinoids, such as docosatetraenoylethanolamide found in wild daga, the compound tetrahydrocannabinol which is an active constituent of the psychoactive drug cannabis; and synthetic analogs of tetrahydrocannabinol. CB1 is antagonized by the phytocannabinoid tetrahydrocannabivarin at low doses and at higher doses, it activate the CB1 receptor as an agonist, but with less potency than tetrahydrocannabinol. [11] [12] [13]

The primary endogenous agonist of the human CB1 receptor is anandamide. [5]

Structure

The CB1 receptor shares the structure characteristic of all G-protein-coupled receptors, possessing seven transmembrane domains connected by three extracellular and three intracellular loops, an extracellular N-terminal tail, and an intracellular C-terminal tail. [14] [15] The receptor may exist as a homodimer or form heterodimers or other GPCR oligomers with different classes of G-protein-coupled receptors. Observed heterodimers include A2A–CB1, CB1–D2, OX1–CB1, μOR–CB1, while many more may only be stable enough to exist in vivo. [16] [17] The CB1 receptor possesses an allosteric modulatory binding site. [18]

The CB1 receptor is encoded by the gene CNR1, [19] located on human chromosome 6. [20] Two transcript variants encoding different isoforms have been described for this gene. [19] CNR1 orthologs [21] have been identified in most mammals.

The CNR1 gene has a structure consisting of a single coding-exon and multiple alternative 5' untranslated exons. The CB1 receptor is created by transcription of the last exon on the CNR1 gene. [22]

Mechanism

The CB1 receptor is a pre-synaptic heteroreceptor that modulates neurotransmitter release when activated in a dose-dependent, stereoselective and pertussis toxin-sensitive manner. [19] The CB1 receptor is activated by cannabinoids, generated naturally inside the body (endocannabinoids) or exogenously, normally through cannabis or a related synthetic compound.

Research suggests that the majority of CB1 receptors are coupled through Gi/o proteins. Upon activation, CB1 receptor exhibits its effects mainly through activation of Gi, which decreases intracellular cAMP concentration by inhibiting its production enzyme, adenylate cyclase, and increases mitogen-activated protein kinase (MAP kinase) concentration. Alternatively, in some rare cases CB1 receptor activation may be coupled to Gs proteins, which stimulate adenylate cyclase. [17] cAMP is known to serve as a second messenger coupled to a variety of ion channels, including the positively influenced inwardly rectifying potassium channels (=Kir or IRK), [23] and calcium channels, which are activated by cAMP-dependent interaction with such molecules as protein kinase A (PKA), protein kinase C (PKC), Raf-1, ERK, JNK, p38, c-fos, c-jun, and others. [24]

In terms of function, the inhibition of intracellular cAMP expression shortens the duration of pre-synaptic action potentials by prolonging the rectifying potassium A-type currents, which is normally inactivated upon phosphorylation by PKA. This inhibition grows more pronounced when considered with the effect of activated CB1 receptors to limit calcium entry into the cell, which does not occur through cAMP but by a direct G-protein-mediated inhibition. As presynaptic calcium entry is a requirement for vesicle release, this function will decrease the transmitter that enters the synapse upon release. [20] The relative contribution of each of these two inhibitory mechanisms depends on the variance of ion channel expression by cell type.

The CB1 receptor can also be allosterically modulated by synthetic ligands [25] in a positive [26] and negative [27] manner. In vivo exposure to tetrahydrocannabinol impairs long-term potentiation and leads to a reduction of phosphorylated CREB. [28]

The signaling properties of activated CB1 are furthermore modified by the presence of SGIP1, that hinders receptor internalization and decreases ERK1/2 signalling while augmenting the interaction with GRK3, β-arrestin-2. [29] [30]

In summary, CB1 receptor activity has been found to be coupled to certain ion channels, in the following manner: [17]

Expression

CB1 receptors are localized throughout the central and peripheral nervous systems, particularly on axon terminals in the cerebellum, hippocampus, basal ganglia, frontal cortex, amygdala, hypothalamus, and midbrain. [22] The CB1 receptor is primarily expressed in the presynaptic terminals of GABAergic (amygdala and cerebellum), glutamatergic (cortex, hippocampus and amygdala), dopaminergic, GABAergic interneurons, cholinergic neurons, noradrenergic, and serotonergic neurons. [31] Acting as a neuromodulator, the CB1 receptor inhibits the release of both excitatory and inhibitory neurotransmitters including acetylcholine, glutamate, GABA, noradrenaline, 5-HT, dopamine, D-aspartate, and cholecystokinin. [22] Repeated administration of receptor agonists may result in receptor internalization and/or a reduction in receptor protein signaling. [17]

The inverse agonist MK-9470 makes it possible to produce in vivo images of the distribution of CB1 receptors in the human brain with positron emission tomography. [32]

Brain

The CB1 receptor is recognized as the most abundant metabotropic receptor in the brain. [10] CB1 receptors are found moderately to highly expressed within the cerebral cortex (cingulate gyrus, prefrontal cortex, and hippocampus), periaqueductal gray, hypothalamus, amygdala, cerebellum, and basal ganglia (globus pallidus, substantia nigra). [31] Varying levels of CB1 can also be detected in the olfactory bulb, cortical regions (neocortex, pyriform cortex), parts of basal ganglia, thalamic, hypothalamic, and brainstem nuclei, as well as in subcortical regions (e.g., the septal region), and cerebellar cortex. [24]

Cnr1 is widely expressed in all major regions of the postnatal day 14 mouse brain, but is conspicuously absent in much of the thalamus. CNR1, ISH, mouse.jpg
Cnr1 is widely expressed in all major regions of the postnatal day 14 mouse brain, but is conspicuously absent in much of the thalamus.

CB1 receptors are expressed most densely in the central nervous system and are largely responsible for mediating the effects of cannabinoid binding in the brain. Endocannabinoids released by a depolarized neuron bind to CB1 receptors on pre-synaptic glutamatergic and GABAergic neurons, resulting in a respective decrease in either glutamate or GABA release. Limiting glutamate release causes reduced excitation, while limiting GABA release suppresses inhibition, a common form of short-term plasticity in which the depolarization of a single neuron induces a reduction in GABA-mediated inhibition, in effect exciting the postsynaptic cell. [20]

Brainstem

High expression of CB1 is found in brainstem medullary nuclei, including the nucleus of the solitary tract and area postrema. CB1 receptor is relatively low in medullary respiratory brainstem control centers. [31]

Hippocampal formation

CB1 mRNA transcripts are abundant in GABAergic interneurons of the hippocampus, indirectly reflecting the expression of these receptors and elucidating the established effect of cannabinoids on memory. These receptors are densely located in cornu ammonis pyramidal cells, which are known to release glutamate. Cannabinoids suppress the induction of LTP and LTD in the hippocampus by inhibiting these glutamatergic neurons. By reducing the concentration of glutamate released below the threshold necessary to depolarize the postsynaptic NMDA receptor, [20] a receptor known to be directly related to the induction of LTP and LTD, cannabinoids are a crucial factor in the selectivity of memory. These receptors are highly expressed by GABAergic interneurons as well as glutamatergic principal neurons. However, a higher density is found within GABAergic cells. [33] This means that, although synaptic strength/frequency, and thus potential to induce LTP, is lowered, net hippocampal activity is raised. In addition, CB1 receptors in the hippocampus indirectly inhibit the release of acetylcholine. This serves as the modulatory axis opposing GABA, decreasing neurotransmitter release. Cannabinoids also likely play an important role in the development of memory through their neonatal promotion of myelin formation, and thus the individual segregation of axons.

Basal ganglia

CB1 receptors are expressed throughout the basal ganglia and have well-established effects on movement in rodents. As in the hippocampus, these receptors inhibit the release of glutamate or GABA transmitter, resulting in decreased excitation or reduced inhibition based on the cell they are expressed in. Consistent with the variable expression of both excitatory glutamate and inhibitory GABA interneurons in both the basal ganglia's direct and indirect motor loops, synthetic cannabinoids are known to influence this system in a dose-dependent triphasic pattern. Decreased locomotor activity is seen at both higher and lower concentrations of applied cannabinoids, whereas an enhancement of movement may occur upon moderate dosages. [20] However, these dose-dependent effects have been studied predominately in rodents, and the physiological basis for this triphasic pattern warrants future research in humans. Effects may vary based on the site of cannabinoid application, input from higher cortical centers, and whether drug application is unilateral or bilateral.

Cerebellum and neocortex

The role of the CB1 receptor in the regulation of motor movements is complicated by the additional expression of this receptor in the cerebellum and neocortex, two regions associated with the coordination and initiation of movement. Research suggests that anandamide is synthesized by Purkinje cells and acts on presynaptic receptors to inhibit glutamate release from granule cells or GABA release from the terminals of basket cells. In the neocortex, these receptors are concentrated on local interneurons in cerebral layers II-III and V-VI. [20] Compared to rat brains, humans express more CB1 receptors in the cerebral cortex and amygdala and less in the cerebellum, which may help explain why motor function seems to be more compromised in rats than humans upon cannabinoid application. [33]

Spine

Many of the documented analgesic effects of cannabinoids are based on the interaction of these compounds with CB1 receptors on spinal cord interneurons in the superficial levels of the dorsal horn, known for its role in nociceptive processing. In particular, the CB1 is heavily expressed in layers 1 and 2 of the spinal cord dorsal horn and in lamina 10 by the central canal. Dorsal root ganglion also express these receptors, which target a variety of peripheral terminals involved in nociception. Signals on this track are also transmitted to the periaqueductal gray (PAG) of the midbrain. Endogenous cannabinoids are believed to exhibit an analgesic effect on these receptors by limiting both GABA and glutamate of PAG cells that relate to nociceptive input processing, a hypothesis consistent with the finding that anandamide release in the PAG is increased in response to pain-triggering stimuli. [20]

Other

CB1 is expressed on several types of cells in pituitary gland, thyroid gland, and possibly in the adrenal gland. [24] CB1 is also expressed in several cells relating to metabolism, such as fat cells, muscle cells, liver cells (and also in the endothelial cells, Kupffer cells and stellate cells of the liver), and in the digestive tract. [24] It is also expressed in the lungs and the kidney.

CB1 is present on Leydig cells and human sperms. In females, it is present in the ovaries, oviducts myometrium, decidua, and placenta. It has also been implicated in the proper development of the embryo. [24]

CB1 is also expressed in the retina. In the retina, they are expressed in the photoreceptors, inner plexiform, outer plexiform, bipolar cells, ganglion cells, and retinal pigment epithelium cells. [34] In the visual system, cannabinoids agonist induce a dose dependent modulation of calcium, chloride and potassium channels. This alters vertical transmission between photoreceptor, bipolar and ganglion cells. Altering vertical transmission in turn results in the way vision is perceived. [35]

Physiological and pathological conditions

The activation of CB1 in the human body generally inhibits neurotransmitter release, controls pain, regulates metabolism, and monitors the cardiovascular system. [36] CB1 receptors are implicated in a number of physiological processes related to the central nervous system (CNS) including brain development, learning and memory, motor behavior, regulation of appetite, body temperature, pain perception, and inflammation. [10]

The localization of CB1 receptors is expressed in several neuronal types, including GABAergic, glutamatergic, and serotonergic neurons. CB1 receptors localized in GABAergic neurons can modulate food intake, learning and memory processes, drug addiction, and related behaviors. CB1 receptors localized in glutamatergic neurons are capable of mediating olfactory processes, neuroprotection, social behaviors, anxiety, and fear memories. The localization of CB1 receptors in serotonergic neurons can regulate emotional responses. [10]

Clinically, CB1 is a direct drug target for addiction, pain, epilepsy, and obesity. [36] CB1 receptor function is involved with several psychiatric, neurological, neurodevelopmental, and neurodegenerative disorders including Huntington's disease (HD), multiple sclerosis (MS), and Alzheimer's disease (AD). Major loss of CB1 receptors is reported in patients with HD. However, stimulation of the CB1 receptor has potential to reduce the progression of HD. Improvements from use of CB agonist in MS are associated with the activation of CB1 and CB2 receptors, leading to dual anti-inflammatory and neuroprotective effects throughout the CNS. Similarly, activation of CB1 and CB2 receptors could provide neuroprotective effects against amyloid-β (Aβ) toxicity in AD. [37] In several brain regions, including the dorsolateral prefrontal cortex (DLPFC) and hippocampus, dysregulation of the CB1 receptor is implicated in the development of schizophrenia. Abnormal functioning of the CB1 receptor compromises intricate neural systems that are responsible for controlling cognition and memory, which contributes to the pathology. [22] PET imaging modalities implicate that alterations of CB1 levels in certain brain systems are strongly associated with schizophrenia symptoms. Neurobehavioral disorders, such as attention deficit hyperactivity disorder (ADHD), are associated with genetic variants of CNR1 in rat models of ADHD. [31]

Use of antagonists

Selective CB1 agonists may be used to isolate the effects of the receptor from the CB2 receptor, as most cannabinoids and endocannabinoids bind to both receptor types. [20] CB1 selective antagonists such as rimonabant are used for weight reduction and smoking cessation. A substantial number of antagonists of the CB1 receptor have been discovered and characterized. TM38837 has been developed as a CB1 receptor antagonist that is restricted to targeting only peripheral CB1 receptors.

Ligands

Agonists

Selective

Unspecified efficacy

Partial

Endogenous
Phyto

Full

Endogenous
Synthetic

Allosteric agonist

Antagonists

Inverse agonists

Allosteric modulators

Binding affinities

CB1 affinity (Ki)Efficacy towards CB1CB2 affinity (Ki)Efficacy towards CB2TypeReferences
Anandamide 78 nMPartial agonist370 nMPartial agonistEndogenous
N-Arachidonoyl dopamine 250 nMAgonist12000 nM ?Endogenous [41]
2-Arachidonoylglycerol 58.3 nMFull agonist145 nMFull agonistEndogenous [41]
2-Arachidonyl glyceryl ether 21 nMFull agonist480 nMFull agonistEndogenous
Tetrahydrocannabinol 10 nMPartial agonist24 nMPartial agonistPhytogenic [42]
EGCG 33600 nMAgonist50000+ nM ?Phytogenic
AM-1221 52.3 nMAgonist0.28 nMAgonistSynthetic [43]
AM-1235 1.5 nMAgonist20.4 nMAgonistSynthetic [44]
AM-2232 0.28 nMAgonist1.48 nMAgonistSynthetic [44]
UR-144 150 nMFull agonist1.8 nMFull agonistSynthetic [45]
JWH-007 9.0 nMAgonist2.94 nMAgonistSynthetic [46]
JWH-015 383 nMAgonist13.8 nMAgonistSynthetic [46]
JWH-018 9.00 ± 5.00 nMFull agonist2.94 ± 2.65 nMFull agonistSynthetic [47]

Evolution

The CNR1 gene is used in animals as a nuclear DNA phylogenetic marker. [21] This intronless gene has first been used to explore the phylogeny of the major groups of mammals, [48] and contributed to reveal that placental orders are distributed into five major clades: Xenarthra, Afrotheria, Laurasiatheria, Euarchonta, and Glires. CNR1 has also proven useful at lower taxonomic levels, such as rodents, [49] [50] and for the identification of dermopterans as the closest primate relatives. [51]

Paralogues

Source: [52]

See also

Related Research Articles

<span class="mw-page-title-main">Neurotransmitter</span> Chemical substance that enables neurotransmission

A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.

<span class="mw-page-title-main">Cannabinoid</span> Compounds found in cannabis

Cannabinoids are several structural classes of compounds found in the cannabis plant primarily and most animal organisms or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoactive compound in cannabis. Cannabidiol (CBD) is also a major constituent of temperate cannabis plants and a minor constituent in tropical varieties. At least 100 distinct phytocannabinoids have been isolated from cannabis, although only four have been demonstrated to have a biogenetic origin. It was reported in 2020 that phytocannabinoids can be found in other plants such as rhododendron, licorice and liverwort, and earlier in Echinacea.

<span class="mw-page-title-main">Cannabinoid receptor</span> Group of receptors to cannabinoid compounds

Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system of vertebrates– a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains. Cannabinoid receptors are activated by three major groups of ligands:

<span class="mw-page-title-main">Cannabinol</span> Naturally-occurring cannabinoid

Cannabinol (CBN) is a mildly psychoactive phytocannabinoid that acts as a low affinity partial agonist at both CB1 and CB2 receptors. This activity at CB1 and CB2 receptors constitutes interaction of CBN with the endocannabinoid system (ECS).

<span class="mw-page-title-main">Tetrahydrocannabivarin</span> Homologue of tetrahydrocannabinol

Tetrahydrocannabivarin is a homologue of tetrahydrocannabinol (THC) having a propyl (3-carbon) side chain instead of pentyl (5-carbon), making it non-psychoactive in lower doses. It has been shown to exhibit neuroprotective activity, appetite suppression, glycemic control and reduced side effects compared to THC, making it a potential treatment for management of obesity and diabetes. THCV was studied by Roger Adams as early as 1942.

<span class="mw-page-title-main">Neurotransmission</span> Impulse transmission between neurons

Neurotransmission is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron, and bind to and react with the receptors on the dendrites of another neuron a short distance away. A similar process occurs in retrograde neurotransmission, where the dendrites of the postsynaptic neuron release retrograde neurotransmitters that signal through receptors that are located on the axon terminal of the presynaptic neuron, mainly at GABAergic and glutamatergic synapses.

Depolarization-induced suppression of inhibition is the classical and original electrophysiological example of endocannabinoid function in the central nervous system. Prior to the demonstration that depolarization-induced suppression of inhibition was dependent on the cannabinoid CB1 receptor function, there was no way of producing an in vitro endocannabinoid mediated effect.

<span class="mw-page-title-main">WIN 55,212-2</span> Chemical compound

WIN 55,212-2 is a chemical described as an aminoalkylindole derivative, which produces effects similar to those of cannabinoids such as tetrahydrocannabinol (THC) but has an entirely different chemical structure.

<span class="mw-page-title-main">Endocannabinoid system</span> Biological system of neurotransmitters

The endocannabinoid system (ECS) is a biological system composed of endocannabinoids, which are neurotransmitters that bind to cannabinoid receptors, and cannabinoid receptor proteins that are expressed throughout the central nervous system and peripheral nervous system. The endocannabinoid system is still not fully understood, but may be involved in regulating physiological and cognitive processes, including fertility, pregnancy, pre- and postnatal development, various activity of immune system, appetite, pain-sensation, mood, and memory, and in mediating the pharmacological effects of cannabis. The ECS plays an important role in multiple aspects of neural functions, including the control of movement and motor coordination, learning and memory, emotion and motivation, addictive-like behavior and pain modulation, among others.

A heteroreceptor is a receptor regulating the synthesis and/or the release of mediators other than its own ligand.

<span class="mw-page-title-main">NAGly receptor</span> Protein-coding gene in the species Homo sapiens

N-Arachidonyl glycine receptor, also known as G protein-coupled receptor 18 (GPR18), is a protein that in humans is encoded by the GPR18 gene. Along with the other previously orphan receptors GPR55 and GPR119, GPR18 has been found to be a receptor for endogenous lipid neurotransmitters, several of which also bind to cannabinoid receptors. It has been found to be involved in the regulation of intraocular pressure.

<span class="mw-page-title-main">GPR55</span> Protein-coding gene in the species Homo sapiens

G protein-coupled receptor 55 also known as GPR55 is a G protein-coupled receptor that in humans is encoded by the GPR55 gene.

<span class="mw-page-title-main">Cannabinoid receptor 2</span> Mammalian protein found in Homo sapiens

The cannabinoid receptor 2(CB2), is a G protein-coupled receptor from the cannabinoid receptor family that in humans is encoded by the CNR2 gene. It is closely related to the cannabinoid receptor 1 (CB1), which is largely responsible for the efficacy of endocannabinoid-mediated presynaptic-inhibition, the psychoactive properties of tetrahydrocannabinol (THC), the active agent in cannabis, and other phytocannabinoids. The principal endogenous ligand for the CB2 receptor is 2-Arachidonoylglycerol (2-AG).

<span class="mw-page-title-main">JWH-015</span> Chemical compound

JWH-015 is a chemical from the naphthoylindole family that acts as a subtype-selective cannabinoid agonist. Its affinity for CB2 receptors is 13.8 nM, while its affinity for CB1 is 383 nM, meaning that it binds almost 28 times more strongly to CB2 than to CB1. However, it still displays some CB1 activity, and in some model systems can be very potent and efficacious at activating CB1 receptors, and therefore it is not as selective as newer drugs such as JWH-133. It has been shown to possess immunomodulatory effects, and CB2 agonists may be useful in the treatment of pain and inflammation. It was discovered and named after John W. Huffman.

A cannabinoid receptor antagonist, also known simply as a cannabinoid antagonist or as an anticannabinoid, is a type of cannabinoidergic drug that binds to cannabinoid receptors (CBR) and prevents their activation by endocannabinoids. They include antagonists, inverse agonists, and antibodies of CBRs. The discovery of the endocannabinoid system led to the development of CB1 receptor antagonists. The first CBR inverse agonist, rimonabant, was described in 1994. Rimonabant blocks the CB1 receptor selectively and has been shown to decrease food intake and regulate body-weight gain. The prevalence of obesity worldwide is increasing dramatically and has a great impact on public health. The lack of efficient and well-tolerated drugs to cure obesity has led to an increased interest in research and development of CBR antagonists. Cannabidiol (CBD), a naturally occurring cannabinoid and a non-competitive CB1/CB2 receptor antagonist, as well as Δ9-tetrahydrocannabivarin (THCV), a naturally occurring cannabinoid, modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. CBD is a very low-affinity CB1 ligand, that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant.

<i>N</i>-Acylethanolamine Class of chemical compounds

An N-acylethanolamine (NAE) is a type of fatty acid amide where one of several types of acyl groups is linked to the nitrogen atom of ethanolamine, and highly metabolic formed by intake of essential fatty acids through diet by 20:4, n-6 and 22:6, n-3 fatty acids, and when the body is physically and psychologically active,. The endocannabinoid signaling system (ECS) is the major pathway by which NAEs exerts its physiological effects in animal cells with similarities in plants, and the metabolism of NAEs is an integral part of the ECS, a very ancient signaling system, being clearly present from the divergence of the protostomian/deuterostomian, and even further back in time, to the very beginning of bacteria, the oldest organisms on Earth known to express phosphatidylethanolamine, the precursor to endocannabinoids, in their cytoplasmic membranes. Fatty acid metabolites with affinity for CB receptors are produced by cyanobacteria, which diverged from eukaryotes at least 2000 Million years ago (MYA), by brown algae which diverged about 1500 MYA, by sponges, which diverged from eumetazoans about 930 MYA, and a lineages that predate the evolution of CB receptors, as CB1 – CB2 duplication event may have occurred prior to the lophotrochozoan-deuterostome divergence 590 MYA. Fatty acid amide hydrolase (FAAH) evolved relatively recently, either after the evolution of fish 400 MYA, or after the appearance of mammals 300 MYA, but after the appearance of vertebrates. Linking FAAH, vanilloid receptors (VR1) and anandamide implies a coupling among the remaining ‘‘older’’ parts of the endocannabinoid system, monoglyceride lipase (MGL), CB receptors, that evolved prior to the metazoan–bilaterian divergence, but were secondarily lost in the Ecdysozoa, and 2-Arachidonoylglycerol (2-AG).

<span class="mw-page-title-main">Abnormal cannabidiol</span> Synthetic, cannabinoid-like compound

Abnormal cannabidiol (Abn-CBD) is a synthetic regioisomer of cannabidiol, which unlike most other cannabinoids produces vasodilator effects, lowers blood pressure, and induces cell migration, cell proliferation and mitogen-activated protein kinase activation in microglia, but without producing any psychoactive or sedative effects. Abn-CBD can be found as an impurity in synthetic cannabidiol.

<span class="mw-page-title-main">AM-630</span> Chemical compound

AM-630 (6-Iodopravadoline) is a drug that acts as a potent and selective inverse agonist for the cannabinoid receptor CB2, with a Ki of 32.1 nM at CB2 and 165x selectivity over CB1, at which it acted as a weak partial agonist. It is used in the study of CB2 mediated responses and has been used to investigate the possible role of CB2 receptors in the brain. AM-630 is significant as one of the first indole derived cannabinoid ligands substituted on the 6-position of the indole ring, a position that has subsequently been found to be important in determining affinity and efficacy at both the CB1 and CB2 receptors, and has led to the development of many related derivatives.

<span class="mw-page-title-main">SR-144,528</span> Chemical compound

SR144528 is a drug that acts as a potent and highly selective CB2 receptor inverse agonist, with a Ki of 0.6 nM at CB2 and 400 nM at the related CB1 receptor. It is used in scientific research for investigating the function of the CB2 receptor, as well as for studying the effects of CB1 receptors in isolation, as few CB1 agonists that do not also show significant activity as CB2 agonists are available. It has also been found to be an inhibitor of sterol O-acyltransferase, an effect that appears to be independent from its action on CB2 receptors.

References

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