Cannabinoid receptor type 1 (CB₁), also known as cannabinoid receptor 1, is a G protein-coupled cannabinoid receptor that in humans is encoded by the ''CNR1''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. The human CB₁ receptor is expressed in the

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain ...

and

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

. It is activated by: endocannabinoids, a group of retrograde neurotransmitters that include anandamide and

2-arachidonoylglycerol 2-Arachidonoylglycerol (2-AG) is an endocannabinoid, an endogenous agonist of the CB1 receptor and the primary endogenous ligand for the CB2 receptor. It is an ester formed from the omega-6 fatty acid arachidonic acid and glycerol. It is present ...

(2-AG); plant phytocannabinoids, such as the compound THC which is an active ingredient of the

psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent or psychotropic drug is a chemical substance, that changes functions of the nervous system, and results in alterations in perception, mood, consciousness, cognition or behavior. ...

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: ''Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternatively ...

; and, synthetic analogs of THC. CB1 is antagonized by the phytocannabinoid tetrahydrocannabivarin (THCV). The primary endogenous agonist of the human CB₁ receptor is anandamide.

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. The receptor may exist as a homodimer or form

heterodimer In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has ...

s or other GPCR oligomers with different classes of G-protein-coupled receptors. Observed heterodimers include A_2A–CB₁, CB₁–D₂, OX₁–CB₁, μOR–CB_1, while many more may only be stable enough to exist in vivo. The CB₁ receptor possesses an

allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a Receptor (biochemistry), receptor to change that receptor's response to stimulus. Some of them, like benzodiazepines, are drugs. The site that an allos ...

y binding site.

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. The CB₁ receptor is activated by

cannabinoids Cannabinoids () are several structural classes of compounds found in the cannabis plant primarily and most animal organisms (although insects lack such receptors) or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tet ...

, generated naturally inside the body ( endocannabinoids) or introduced into the body as

or a related

synthetic Synthetic things are composed of multiple parts, often with the implication that they are artificial. In particular, 'synthetic' may refer to: Science * Synthetic chemical or compound, produced by the process of chemical synthesis * Synthetic o ...

compound. Research suggests that the majority of CB₁ receptors are coupled through G_i/o proteins. Upon activation, CB₁ receptor exhibits its effects mainly through activation of G_i, which decreases intracellular cAMP concentration by inhibiting its production

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

, adenylate cyclase, and increases

mitogen-activated protein kinase A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of protein kinase that is specific to the amino acids serine and threonine (i.e., a serine/threonine-specific protein kinase). MAPKs are involved in directing cellular responses to ...

(MAP kinase) concentration. Alternatively, in some rare cases CB₁ receptor activation may be coupled to G_s proteins, which stimulate adenylate cyclase. 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), and

calcium channel A calcium channel is an ion channel which shows selective permeability to calcium ions. It is sometimes synonymous with voltage-gated calcium channel, although there are also ligand-gated calcium channels. Comparison tables The following tables e ...

s, which are activated by cAMP-dependent interaction with such molecules as protein kinase A (PKA),

protein kinase C In cell biology, Protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and t ...

(PKC),

Raf-1 RAF proto-oncogene serine/threonine-protein kinase, also known as proto-oncogene c-RAF or simply c-Raf or even Raf-1, is an enzyme that in humans is encoded by the ''RAF1'' gene. The c-Raf protein is part of the ERK1/2 pathway as a MAP kinase ( ...

, ERK,

JNK c-Jun N-terminal kinases (JNKs), were originally identified as kinases that bind and phosphorylate c-Jun on Ser-63 and Ser-73 within its transcriptional activation domain. They belong to the mitogen-activated protein kinase family, and are ...

, p38,

c-fos Protein c-Fos is a proto-oncogene that is the human homolog of the retroviral oncogene v-fos. It is encoded in humans by the ''FOS'' gene. It was first discovered in rat fibroblasts as the transforming gene of the FBJ MSV (Finkel–Biskis–Jinkin ...

c-jun Transcription factor Jun is a protein that in humans is encoded by the ''JUN'' gene. c-Jun, in combination with protein c-Fos, forms the AP-1 early response transcription factor. It was first identified as the Fos-binding protein p39 and only lat ...

, and others. 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. 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

allosteric In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site. The site to which the effector binds is termed the ''allosteric site ...

ally modulated by synthetic ligands in a positive and negative manner. ''

In vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and ...

'' exposure to THC impairs long-term potentiation and leads to a reduction of phosphorylated CREB. The signaling properties of activated CB₁ are furthermore modified by the presence of

SGIP1 SH3-containing GRB2-like protein 3-interacting protein 1 is a protein that in humans is encoded by the ''SGIP1'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredi ...

, that hinders receptor internalization and decreases ERK1/2 signalling while augmenting the interaction with GRK3, β-arrestin-2. In summary, CB₁ receptor activity has been found to be coupled to certain ion channels, in the following manner: * Positively to inwardly rectifying and A-type outward potassium channels. * Negatively to D-type outward potassium channels * Negatively to N-type and P/Q-type calcium channels.

Expression

The CB₁ receptor is encoded by the gene ''CNR1,'' located on human chromosome 6. Two transcript variants encoding different isoforms have been described for this gene. CNR1 orthologs have been identified in most mammals. The CB₁ receptor is expressed pre-synaptically at both glutaminergic and GABAergic interneurons and, in effect, acts as a neuromodulator to inhibit release of

glutamate Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can syn ...

and GABA. Repeated administration of receptor agonists may result in receptor internalization and/or a reduction in receptor protein signalling. The

inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agon ...

MK-9470 MK-9470 is a synthetic compound, which binds to the CB1 cannabinoid receptor and functions as an inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response ...

makes it possible to produce ''in vivo'' images of the distribution of CB₁ receptors in the human brain with

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in Metabolism, metabolic processes, and in other physiological activities including bl ...

Brain

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 Plasticity may refer to: Science * Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load * Neuroplasticity, in neuroscience, how entire brain structures, and the brain it ...

in which the depolarization of a single neuron induces a reduction in GABA-mediated inhibition, in effect exciting the postsynaptic cell. Varying levels of CB₁ expression can be detected in the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...

, cortical regions (

neocortex The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, sp ...

, pyriform cortex,

hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, a ...

, and

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verteb ...

), several parts of

basal ganglia The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei, of varied origin, in the brains of vertebrates. In humans, and some primates, there are some differences, mainly in the division of the globus pallidus into an extern ...

thalamic The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

and

hypothalamic The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus i ...

nuclei, and other subcortical regions (e.g., the

septal region The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loca ...

), cerebellar cortex, and

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...

nuclei (e.g., the periaqueductal gray).

Hippocampal formation

CB₁

mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of Protein biosynthesis, synthesizing a protein. mRNA is ...

transcripts are abundant in GABAergic interneurons of the

, indirectly reflecting the expression of these receptors and elucidating the established effect of cannabinoids on

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, ...

. These receptors are densely located in cornu ammonis pyramidal cells, which are known to release

. 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 receptor NMDA, 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. 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 Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...

. 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 Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...

formation, and thus the individual segregation of axons.

Basal ganglia

CB₁ receptors are expressed throughout the

and have well-established effects on movement in

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are nat ...

. As in the

, these receptors inhibit the release of

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 Synthetic cannabinoids are a class of designer drug molecules that bind to the same receptors to which cannabinoids (THC, CBD and many others) in cannabis plants attach. These novel psychoactive substances should not be confused with synthetic ...

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

, whereas an enhancement of movement may occur upon moderate dosages. 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 The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...

and

, 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. 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.

Spine

Many of the documented analgesic effects of cannabinoids are based on the interaction of these compounds with CB₁ receptors on

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

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.

Other

CB₁ is expressed on several types of cell in

pituitary gland In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The ...

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue cal ...

, and possibly in the

adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which ...

. CB₁ is also expressed in several cells relating to metabolism, such as

fat cells Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. I ...

, muscle cells, liver cells (and also in the endothelial cells, Kupffer cells and

stellate cells Stellate cells are neurons in the central nervous system, named for their star-like shape formed by dendritic processes radiating from the cell body. Many stellate cells are GABAergic and are located in the molecular layer of the cerebellum. S ...

of the

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

), and in the digestive tract. It is also expressed in the

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of th ...

and the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...

. CB₁ is present on Leydig cells and human

sperms Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...

. In females, it is present in the

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

, oviducts myometrium, decidua, and

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...

. It has also been implicated in the proper development of the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

. CB₁ is also expressed in the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

. In the retina, they are expressed in the photoreceptors, inner plexiform, outer plexiform, bipolar cells, ganglion cells, and retinal pigment epithelium cells. 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.

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. CB₁ selective antagonists are used for weight reduction and smoking cessation (see

Rimonabant Rimonabant (also known as SR141716; trade names Acomplia, Zimulti) is an anorectic antiobesity drug that was first approved in Europe in 2006 but was withdrawn worldwide in 2008 due to serious psychiatric side effects; it was never approved in t ...

). A substantial number of antagonists of the CB1 receptor have been discovered and characterized.

TM38837 TM-38837 is a small molecule inverse agonist/antagonist of the CB1 cannabinoid receptor, with peripheral selectivity. It is being developed for the treatment of obesity and metabolic disorders by 7TM Pharma. The company has announced phase I cl ...

has been developed as a CB1 receptor antagonist that is restricted to targeting only peripheral CB1 receptors.

Ligands

Agonists

Minocycline Minocycline, sold under the brand name Minocin among others, is a tetracycline antibiotic medication used to treat a number of bacterial infections such as pneumonia. It is generally less preferred than the tetracycline doxycycline. It is also ...

* Dronabinol

Selective

* Epigallocatechin *

Epicatechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from ''catechu'', which is the tannic ...

Kavain Kavain is the main kavalactone found mostly in the roots of the kava plant. Pharmacology Kavain has anticonvulsive properties, attenuating vascular smooth muscle contraction through interactions with voltage-dependent and channels. How this ef ...

Yangonin Yangonin is one of the six major kavalactones found in the kava plant. It has been shown to possess binding affinity for the cannabinoid receptor CB1 (Ki = 0.72 μM), and selectivity vs. the CB2 receptor (Ki >10 μM) where it behaves as an ago ...

Oleamide Oleamide is an organic compound with the formula CH3(CH2)7CH=CH(CH2)7CONH2(. It is the amide derived from the fatty acid oleic acid. It is a colorless waxy solid and occurs in nature. Sometimes labeled as a fatty acid primary amide (FAPA), it is ...

Unspecified efficacy

* N-Arachidonoyl dopamine *

Cannabinol Cannabinol (CBN) is a mildly psychoactive cannabinoid 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). CBN w ...

* HU-210 *

11-Hydroxy-THC 11-Hydroxy-Δ9-tetrahydrocannabinol (11-OH-Δ9-THC, alternatively numbered as 7-OH-Δ1-THC), usually referred to as 11-hydroxy-THC, is the main active metabolite of tetrahydrocannabinol (THC), which is formed in the body after THC is consumed. A ...

Levonantradol Levonantradol (CP 50,556-1) is a synthetic cannabinoid analog of dronabinol (Marinol) developed by Pfizer in the 1980s. It is around 30x more potent than THC, and exhibits antiemetic and analgesic effects via activation of CB1 and CB2 cannabinoi ...

Partial

=Endogenous

= *

2-Arachidonyl glyceryl ether 2-Arachidonyl glyceryl ether (2-AGE, Noladin ether) is a putative endocannabinoid discovered by Lumír Hanuš and colleagues at the Hebrew University of Jerusalem, Israel. It is an ether formed from the alcohol analog of arachidonic acid and gl ...

=Phyto/synthetic

= *

JWH-073 JWH-073, a synthetic cannabinoid, is an analgesic chemical from the naphthoylindole family that acts as a partial agonist at both the CB1 and CB2 cannabinoid receptors. It is somewhat selective for the CB1 subtype, with affinity at this subtype ap ...

Tetrahydrocannabinol Tetrahydrocannabinol (THC) is the principal psychoactive constituent of cannabis and one of at least 113 total cannabinoids identified on the plant. Although the chemical formula for THC (C21H30O2) describes multiple isomers, the term ''THC'' ...

Hexahydrocannabinol Hexahydrocannabinol (HHC) is a hydrogenated derivative of tetrahydrocannabinol. It is a naturally occurring phytocannabinoid that has rarely been identified as a trace component in ''Cannabis sativa'', but can also be produced synthetically by hy ...

Full

=Endogenous

= *

2-Arachidonoylglycerol 2-Arachidonoylglycerol (2-AG) is an endocannabinoid, an endogenous agonist of the CB1 receptor and the primary endogenous ligand for the CB2 receptor. It is an ester formed from the omega-6 fatty acid arachidonic acid and glycerol. It is present ...

=Phyto/synthetic

= * AM-2201 * CP 55,940 * JWH-018 * WIN 55,212-2

Allosteric agonist

* GAT228

Antagonists

* Cannabigerol *

Ibipinabant Ibipinabant (SLV319, BMS-646,256) is a drug used in scientific research which acts as a potent and highly selective CB1 antagonist. It has potent anorectic effects in animals, and was researched for the treatment of obesity, although CB1 antagon ...

Otenabant Otenabant (CP-945,598) is a drug which acts as a potent and highly selective cannabinoid receptor 1, CB1 Antagonist (pharmacology), antagonist. It was developed by Pfizer for the treatment of obesity, but development for this application has bee ...

* Tetrahydrocannabivarin *

Virodhamine Virodhamine (''O''-arachidonoyl ethanolamine; O-AEA) is an endocannabinoid and a nonclassic eicosanoid, derived from arachidonic acid. ''O''-Arachidonoyl ethanolamine is arachidonic acid and ethanolamine joined by an ester linkage, the opposite of ...

(Endogenous CB1 antagonist and CB2 agonist)

Inverse agonists

Taranabant Taranabant (codenamed MK-0364) is a cannabinoid receptor type 1 (CB1) inverse agonist that was investigated as a potential treatment for obesity due to its anorectic effects. It was discovered by Merck & Co. In October 2008, Merck has stopped ...

INV-202

Allosteric modulators

* Lipoxin A4 – endogenous, PAM *

ZCZ-011 ZCZ-011 is a positive allosteric modulator of the cannabinoid CB1 receptor. See also * GAT100 * Org 27569 * PSNCBAM-1 PSNCBAM-1 is a negative allosteric modulator of the cannabinoid CB1 receptor. See also * GAT100 * Org 27569 * ZCZ-011 ...

– PAM *

Pregnenolone Pregnenolone (P5), or pregn-5-en-3β-ol-20-one, is an endogenous steroid and precursor/ metabolic intermediate in the biosynthesis of most of the steroid hormones, including the progestogens, androgens, estrogens, glucocorticoids, and mineraloc ...

– endogenous, NAM * Cannabidiol – NAM * Fenofibrate – NAM *

GAT100 GAT100 is a negative allosteric modulator of the cannabinoid CB1 receptor. See also * Org 27569 * PSNCBAM-1 * ZCZ-011 ZCZ-011 is a positive allosteric modulator of the cannabinoid Cannabinoids () are several structural classes of compou ...

– NAM *

PSNCBAM-1 PSNCBAM-1 is a negative allosteric modulator of the cannabinoid CB1 receptor. See also * GAT100 * Org 27569 * ZCZ-011 ZCZ-011 is a positive allosteric modulator of the cannabinoid Cannabinoids () are several structural classes of compound ...

– NAM *

RVD-Hpα RVD-Hpα (pepcan-12) is an endogenous neuropeptide found in human and mammalian brain, which was originally proposed to act as a selective agonist for the CB1 cannabinoid receptor. It is a 12-amino acid polypeptide having the amino acid seque ...

– NAM

Binding affinities

Evolution

The CNR1 gene is used in animals as a nuclear DNA phylogenetic marker. This intronless gene has first been used to explore the phylogeny of the major groups of mammals, and contributed to reveal that placental orders are distributed into five major clades: Xenarthra, Afrotheria, Laurasiatheria, Euarchonta, and

Glires Glires (, Latin ''glīrēs'' 'dormice') is a clade (sometimes ranked as a grandorder) consisting of rodents and lagomorphs (rabbits, hares, and pikas). The hypothesis that these form a monophyletic group has been long debated based on morphologic ...

. CNR1 has also proven useful at lower

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

levels, such as

, and for the identification of dermopterans as the closest primate relatives.

References

External links

*
Cannabinoid receptor 1
(CNR1) Human Protein Atlas {{DEFAULTSORT:Cannabinoid Receptor Type 1 G protein-coupled receptors