Lecture 13. Cannabinoids

Question 1

What is marijuana/cannabis?

Answer 1

The dried leaves, flowers, stems, and seeds from the hemp plant, Cannabis sativa

Question 2

When was serious interest for the medicinal use of cannabis first shown and why?

Answer 2

1964, identification of the psychoactive ingredient tetrahydrocannabinol (THC)

Question 3

How many compounds do C. sativa and C. indica contain and how many are cannabinoids?

Answer 3

~400 compounds
~100 cannabinoids

Question 4

What is the difference between THC and cannabidiol (CBD)?

Answer 4

CBD has no psychoactive properties

Question 5

What are the central effects of THC?

Answer 5

Impairment of short term memory
Impairment of motor coordination
Altered sense of time
Changes in mood (euphoria/dysphoria)
Impaired cognition
Catalepsy (trance like state)
Hypothermia (often used as a readout of THC action)
Analgesia
Antiemetic
Increase in appetite

Question 6

What are the peripheral effects of THC?

Answer 6

Tachycardia: (even modest doses raise 20 -30 BPM), may increase the chance of myocardial infarction. Older people and those with heart problems are at higher risk
Vasodilation (bloodshot eyes)
Fall in IOP
Bronchodilation

Question 7

What are the pharmacokinetics of cannabis?

Answer 7

Routes of admin: smoking/oral (add to food, edibles)
Effects are very rapid to develop (from smoking) and last for 1-2 hours
Orally takes 30 mins to 2 hours to have effects and then lasts for 4-8 hours
Subject to conjugation and enterohepatic circulation (prolongs duration)
Highly lipohillic, sequestered in body fat and detectable excretion occurs for several weeks after admin

Question 8

What was THC originally thought to do?

Answer 8

THC is highly lipophilic so originally thought to change membrane properties (like general anaesthetics) or act at intracellular receptors

Question 9

When was the first cannabinoid receptor discovered (CB₁)?

Answer 9

1988

Question 10

How was the cannabinoid receptor first discovered?

Answer 10

Used a cannabinoid analogue CP-55,940 (tritium-labeled)
Binding to brain membranes was linear within the range of 10 to 50 micrograms of protein/ml
Specific binding, displaced by tetrahydrocannabinol (Δ-9-THC), and was saturable
Binding decreased by a non-hydrolysable GTP analog, consistent with an allosteric regulation of the putative receptor by a G protein
Suggests that receptor is a GPCR

Question 11

How many cannabinoid receptors are there?

Answer 11

2, CB₁ and CB₂

Question 12

When was CB₂ discovered and why was it discovered?

Answer 12

CB₂ was cloned in 1993 looking for a second cannabinoid receptor that could explain the effects of THC

Question 13

What did the discovery of CB₂ help provide?

Answer 13

A molecular explanation for the effects of cannabinoids on the immune system

Question 14

What do CB₂ receptors inhibit?

Answer 14

The activity of adenylyl cyclase

Question 15

What is the distribution of the cannabinoid receptors within the body?

Answer 15

CB₁ = wide spread distribution in the brain (possibly involved with pain, memory, appetite and euphoria)
CB₂ = more defined pattern: predominantly in cells and tissues of the immune system

Question 16

What is CB₁ coupled to within the brain?

Answer 16

Voltage gated Ca²⁺ and K⁺ channels

Question 17

What does activation of CB₁ result in?

Answer 17

Inhibition of voltage gated Ca²⁺ channels
Activation of K⁺ channels (membrane potential hyperpolarisation)
Inhibits PKA
Some effect on vesicle release
Inhibition of synaptic transmission

Question 18

What happens when CB₁ receptors have been knocked out in mice?

Answer 18

Increased mortality
Leanness, resistance to diet induced obesity, enhanced leptin sensitivity
Loss of THC induced hypothermia
Less pain sensitive in some tests of supraspinal pain responses

Question 19

What was the first endocannabinoid discovered and how and when was it discovered?

Answer 19

Anandamide (N-arachidonyl ethanolamide) was the first endocannabinoid discovered in 1992 by screening porcine brain extracts for compounds that bound to the cannabinoid receptor

Question 20

What does anandamide stimulate?

Answer 20

Cannabinoid receptor-mediated signal transduction

Question 21

What was the second endocannabinoid identified?

Answer 21

The second endocannabinoid identified was 2-arachidonoyl glycerol (2-AG), which was isolated from canine gut and shown to have in vivo effects similar to THC

Question 22

What are all endocannabinoids?

Answer 22

Lipids

Question 23

What are the properties of anandamide and 2-AG?

Answer 23

Produced on demand and not stored in vesicle (unlike classical neurotransmitters)
Produced following elevation of intracellular [Ca²⁺] by calcium-sensitive enzymes

Question 24

How is anandamide obtained?

Answer 24

From the enzymatic hydrolysis of a family of membrane phospholipids, the N-arachidonoyl-phosphatidylethanolamines (NArPE)

Question 25

What catalyses the hydrolysis of NArPE to anandamide?

Answer 25

N-acyl-phosphatidylethanolamine specific phospholipase D (NAPE-PLD), which is Ca²⁺ sensitive

Question 26

How is 2-AG obtained?

Answer 26

The sn-1-acyl-2-arachidonoylglycerols (DAGs) can be directly converted into 2-AG through the action of either of two Ca²⁺ sensitive sn-2-selective DAG lipases (DAGLs), i.e. DAGL-α and DAGL-β

Question 27

Where are the CB receptors on the neurone?

Answer 27

On both the presynaptic and postsynaptic neurone

Question 28

What enzymes remove/break down the endocannabinoids following release?

Answer 28

Monoacylglycerol lipase (MAGL)
Fatty acid amide hydrolase (FAAH)

Question 29

What other cells are CB receptors located on?

Answer 29

Glial cells

Question 30

What is fatty acid amide hydrolase (FAAH)?

Answer 30

FAAH is the main metabolising enzyme for the fatty acid amides (FAAs) which include anandamide

Question 31

What are the differences between normal and FAAH KO mice?

Answer 31

FAAH KO have an analgesic phenotype, showing reduced pain sensation (hot plate test, formalin test, and tail flick test)
FAAH KO display super-sensitivity to exogenous anandamide (as it cannot be broken down)

Question 32

What is the endocannabinoid membrane transporter (EMT) and what does it do?

Answer 32

Fatty-acid–binding protein 5, allows for both signalling from the presynaptic to the postsynaptic and vice versa

Question 33

What is retrograde signalling?

Answer 33

Depolarisation of the postsynaptic neurone triggering the release of cannabinoids to inhibit further GABA release from the presynaptic neurone

Question 34

What causes a calcium rise in glial cells, resulting in ATP and D-serine release?

Answer 34

Cannabinoids

Question 35

What are HU210 and JWH-018?

Answer 35

The first synthetic cannabinoids produced that are much more potent than THC (high affinity and efficacy)
Got out of labs and derivatives and became substances of abuse

Question 36

What is Spice (K2)?

Answer 36

Synthetic chemicals either sprayed on dried, shredded plant material so they can be smoked or sold as liquids to be vaporised and inhaled in e-cigarettes and other devices (liquid incense)

Question 37

Why is Spice so dangerous?

Answer 37

They are not easily detectable in urine and blood samples

Question 38

What does abuse of synthetic cannabinoids lead to?

Answer 38

Associated with a higher prevalence of severe adverse effects, such as hypertension, tachycardia, hallucinations, agitation, seizures, and panic attacks that often require immediate medical care

Question 39

What are the three effects that CBD doesn’t have?

Answer 39

Stimulate appetite
Aid with sleep
Treat fungal infections

Question 40

What is the strongest evidence for a medical effect caused by cannabis?

Answer 40

Anti-emetic effects
Nausea and vomiting associated with cancer chemotherapy a significant problem
Nabilone prescribed in UK (for patients unresponsive to conventional anti-emetics)
Systemic review of oral nabilone, dronabinol. Significantly more effective than standard anti-emetics
Some side effects that are desirable: sedation, drowsiness, euphoria.
Some undesirable side effects: dizziness, dysphoria, depression, hallucinations, paranoia, hypotension

Question 41

Why are cannabinoid derivatives not used for analgesia?

Answer 41

Few human studies, difficult to do research on illegal drugs without proper licenses

Question 42

How can cannabinoids help with appetite stimulation?

Answer 42

Modulates reward pathways to grant a greater reward when the patient eats

Question 43

Why are cannabinoids such as Sativex used to treat multiple sclerosis, but ultimately not recommended?

Answer 43

Several clinical trials show reduction in motor dysfunction and pain, but Sativex is not recommended because it is not a cost effective treatment

Question 44

Why is it thought that cannabinoids are anti-cancer?

Answer 44

Evidence from cell cultures/animal models that THC inhibits the growth of some tumours
Studies on mice and rats suggested that some cannabinoids may have a protective effect against tumour development

Question 45

What are the reported benefits of CBD?

Answer 45

Relieve pain
Treat depression and anxiety
Alleviate cancer-related symptoms
Reduce acne
Neuroprotective properties
Increase cardiac health
Other reported effects include Antipsychotic effects, substance abuse treatment, anti-tumour effects and anti-diabetic actions

Question 46

Do we know how the CBD mechanism of action works?

Answer 46

No

Question 47

What are the side effects and long term risks of taking marijuana?

Answer 47

Temporary hallucinations
Temporary paranoia—extreme and unreasonable distrust of others
Worsening symptoms in patients with schizophrenia
Linked to other mental health problems, such as depression, anxiety, and suicidal thoughts among teens. However, study findings have been mixed