Cannabinoid receptor Anandamide

1. Dr. Ashishkumar Baheti
20/07/2020
JR 2 Pharmacology
Cannabinoid receptor
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2. Introduction
History
Types
Cannabinoid receptor – Location/action/Mechanism
Agonists
Antagonists
Conclusion
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3. Introduction:
• The term Cannabinoid was originally used to describe the family of
naturally occurring chemicals found in cannabis plant e.g. Δ-9-
tetrahydrocannabinol (THC) which is the main active constituent of
cannabis sativa (Marijuana) plant.
• Now all those substances capable of activating cannabinoid
receptors are called cannabinoids.
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4. •At least 5000 years history
•1988 – CB1 receptor was discovered
•1992 – The first endogenous cannabinoid ligand
was discovered in 1992 and named Anandamide.
This name is derived from the Indian Sanskrit
word Anand, meaning bliss, joy or tranquility.
•1993 – CB2 receptors discovered
•1995 – The other EC discovered was 2-
arachidonoylglycerol (2- AG).
History
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5. Types of cannabinoids
cannabinoids
Organic/Natural
Phytocann
abinoids
Endocann
abinoids
Synthetic
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6. Phytocannabinoids
• These are plant derived cannabinoids from cannabis sativa/ hemp
plant. Hashish/Charas/ Bhang /ganja are prepared from various
parts of this plant. The term Marijuana is used to describe any
plant part or extract containing the active principle.
• It has been used for its psychoactive properties for thousands of
years.
• In 1964 tetrahydrocannabinol (THC) was identified as the main
psychoactive component.
• The other components are cannabidiol and cannabinol.
• Most of these compounds are water insoluble.
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7. Pharmacological effects
•CNS – Both psychotomimetic and depressant effects.
•Subjective experiences include euphoria and feeling of
relaxation, with sharpened sensory awareness.
•THC also shows analgesic and antiemetic activity.
•Peripheral actions include vasodilatation, reduction of
intraocular pressure and bronchodilatation.
•Cannabinoids are less liable than opiates, nicotine or alcohol
to cause dependence but may have long term psychological
effects.
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8. Endocannabinoid
Endogenous cannabinoid System (ECS) consists of the
1. Cannabinoid receptors,
2. Endogenous cannabinoids, and
3. Enzymes that synthesize and degrade endocannabinoids.
Endogenous cannabinoids that act as neurotransmitters include 2-arachidonyl
glycerol (2-AG) and anandamide, both of which bind to CB 1 receptors.
These compounds are released at the postsynaptic somatodendritic membrane,
and diffuse through the extracellular space to bind at presynaptic CB 1 receptors,
where they inhibit the release of either glutamate or GABA.
Because of such backward signaling, endocannabinoids are called retrograde
messengers.
1. Cannabinoid
receptor
2. Endogenous
cannabinoids
3. Enzymes that
synthesize and
degrade
endocannabinoid
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9. Endogenous cannabinoid
The endocannabinoids include
• Anandamide (N-arachidonoylethanolamine)
• 2-arachidonoylglycerol (2-AG),
• O-arachidonoylethanolamine (virodhamine),
• N-dihomo- γ-linolenoylethanolamine,
• N-docosatetraenoic-ethanolamine,
• oleamide,
• 2-arachidonyl-glyceryl-ether (2-AGE),
• N-arachidonoyl-dopamine (NADA),
• N-oleoyl-dopamine.
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10. Cannabinoid receptor - CB1 Receptor
1. Location and action in brain
 CB1 receptors are among the most abundant receptors in the brain.
 They are not homogeneously distributed.
 More concentrated in the
• Hippocampus (memory),
• Cerebellum (relevant to loss of coordination),
• Hypothalamus (control of appetite and body temperature),
• Substantia nigra, Mesolimbic dopamine pathways (psychological ‘reward’), and
• Association areas of the cerebral cortex.
 Less concentrated in the
• brain stem (explaining the lack of serious respiratory or cardiovascular toxicity
of the cannabinoids).
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12. CB1 receptors in the brain control appetite and modulate the
hypothalamic neuropeptides to control the size of meals,
and through the adipocytes, regulate lipid metabolism.
Their stimulation by EC increases the food consumption.
By acting at the hypothalamus, EC promote anabolic processes and
inhibit catabolic processes.
It is suggested that overweight and obesity in humans may be related
with hyperactive EC system.
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13. CB1 Receptor
2. Location and action in periphery
CB1 receptors are also expressed in peripheral tissues, for example on
Endothelial cells,
Adipocytes and
Peripheral nerves.
Cannabinoids promote lipogenesis through activation of CB1 receptors
(effect on body weight).
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14. CB2 receptor
 It has only 45% amino acid homology with CB1.
 Location :
Located mainly in lymphoid tissue (spleen, tonsils and thymus as well as
circulating lymphocytes, monocytes and tissue mast cells).
 CB2 receptors are also present on microglia—immune cells in the
CNS.
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15.  Action : little known.
 They are present in atherosclerotic lesions, and CB2 agonists have
antiatherosclerotic effects.
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16. Cannabinoid receptors – signaling mechanism
 Cannabinoid receptors are typical
members of the family of G-protein-
coupled receptors .
 CB1 receptors are linked via Gi/o to
inhibition of adenylyl cyclase and of
voltage-operated calcium channels,
and to activation of G-protein-
sensitive inward-rectifying potassium
(GIRK) channels, causing
hyperpolarisation.
 These effects are similar to those
mediated by opioid receptors. 16

17. Cannabinoid receptors – signaling mechanism
 CB receptors also influence gene
expression, both
 directly by activating mitogen-
activated protein kinase (MAPK),
and
 indirectly by reducing the
activity of protein kinase A (PKA)
as a result of reduced adenylyl
cyclase activity.
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18. Cannabinoid receptors – signaling mechanism
 CB2 Receptors are linked via
Gi/o to adenylyl cyclase, GIRK
channels and mitogenactivated
protein kinase similarly to CB1,
 But they are not linked to
voltage operated calcium
channels (which are not
expressed in immune cells).
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19. Cannabinoid receptors – signaling mechanism
 The actions of endocannabinoids
are terminated by their uptake
into cells, followed by hydrolysis.
 Two enzymes known to break
down anandamide and 2-AG are
fatty acid amide hydrolase
(FAAH)
and monoacylglycerol lipase
(MGL), respectively.
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20. Synthetic cannabinoids
•Cannabinoid receptor agonists were developed in the
1970s in the hope that they would prove useful non-
opioid/non-NSAID analgesics but adverse effects,
particularly sedation and memory impairment, were
problematic.
•Nabilone
•Dronabinol
•Rimonabant - The first selective CB1 receptor
antagonist,, also has inverse agonist properties in some
systems. 20

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27. Potential and actual clinical uses of cannabinoid agonists &
antagonists
Cannabinoid agonists and antagonists are undergoing evaluation for a wide
range of possible indications, including the following.
• Agonists:
– glaucoma (to reduce pressure in the eye)
– nausea/vomiting associated with cancer chemotherapy
– cancer and AIDS (to reduce weight loss)
– neuropathic pain
– head injury
– Tourette’s syndrome (to reduce tics—rapid involuntary movements that
are a feature of this disorder)
– Parkinson’s disease (to reduce involuntary movements caused as an
adverse effect of L-dopa).
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28. Potential and actual clinical uses of cannabinoid agonists and
antagonists
Cannabinoid agonists and antagonists are undergoing evaluation for a wide
range of possible indications, including the following.
• Antagonists:
– obesity
– tobacco dependence
– drug addiction
– alcoholism.
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29. Anandamide
 Endocannabinoid.
 It behaves as a partial cannabinoid receptor agonist in several
functional assays.
 More recent data seem to suggest that Anandamide might interact
directly also with other molecular targets, including non-CB1, non-
CB2 G-protein-coupled receptors (GPCRs) and various ion channels.
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30. NABILONE:
 It is a synthetic cannabinoid.
 It is used to treat nausea and vomiting caused by cancer chemotherapy,
unresponsive to conventional antiemetics.
 The adverse reactions are mainly neurological and comprise drowsiness,
vertigo, visual disturbances, headache, dysphoria, confusion,
hallucinations and psychosis. Hypotension, tachycardia and abdominal
pain may occur.
 Its use is contraindicated in severe hepatic impairment, pregnancy and
breast-feeding.
 The adult dose is 1-2 mg tid.
 Nabilone, was recently reintroduced in the USA for adjunctive therapy in
chronic pain management.
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31. DRONABINOL:
 Synthetic cannabinoid.
 It acts on CB receptors and is used orally to prevent and treat cancer-
chemotherapy-induced nausea and vomiting.
 Because of the availability of more effective agents, dronabinol now is
uncommonly used for the prevention of chemotherapy-induced nausea and
vomiting.
 It acts synergistically with phenothiazine antiemetics. The ADR are wider
than those of nabilone and include drug abuse.
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32. Rimonabant
 It is a selective CB1 antagonist, once promoted as antiobesity
drug.
 It has been, withdrawn from the market due to severe
depression and suicidal tendencies in patients.
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33. Conclusion :
 Cannabinoid receptors are widely distributed in the brain and are also
present in peripheral tissues.
 Most of the agonists and antagonists of the cannabinoid receptor are
under clinical trials.
 The cannabinoid system is likely to emerge as an important drug
target in the future because of its apparent involvement in several
therapeutically desirable effects.
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