Lecture 22; Endocannabinoids

Question 1

What is the pot plant?

Answer 1

Cannibis sativa

Question 2

What is the psycho active substance in POT and what does it do?

Answer 2

–Psychoactive compound Δ9-THC
–hunger
–mood
•Euphoria/anxiety
–other effects

Question 3

What are the principle endocannabinoids in the brain?

Answer 3

2-AG and Anandamide

Question 4

What are the major cannabinoid receptors?

Answer 4

CB1
CB2
GPR18,55 and 115

Question 5

Write some notes on CB1;

Answer 5

1.Cannabinoid Receptor 1 (CB1)
•Widely expressed in CNS
•Presynaptic localization (effects neurotransmission)
•Involved in modulation of synaptic transmission–our focus

Question 6

Write some notes on CB2;

Answer 6

2.CB2
•Expressed in immune cells
•Not involved in synaptic transmission
•Low expression in CNS

Question 7

Write some notes on GPR18,55, and 115

Answer 7

3.GPR18, 55 & 115
•Protein/gene sequence homology
•Activated by endo-(and exo-) cannabinoids
•Unknown involvement in synaptic transmission

Question 8

Describe CB1 structure;

Answer 8

7 TMS
Gi/o coupled

• inhibits adenylate cyclase, lowers cAMP and increases MAP kinase

Question 9

What is the result of CB1 lower cAMP levels?

Answer 9

Net effect of K+and Ca2+channel changes is less Ca2+entry and therefore less neurotransmitter release –CB1 activation inhibits neurotransmitter release

• shortens duration of action potential arriving at the synapse.

Question 10

What is a partial agonist of CB1?

Answer 10

Anandamide

Question 11

How is andandamide produced?

Answer 11

• N-acyltransferase (NAT) -> (NAPE-PLD) -> AEA
• NAT is Ca2+-dependent

Metabolised by FAAH

Question 12

What is anandamide a full agonist of?

Answer 12

TRPV1 has opposing effects of CB1

Question 13

What produces 2AG?

Answer 13

PLC and DGL(a)

Question 14

What is 2AG metabolised by?

Answer 14

MGL

Question 15

What are some other endocannabinoids?

Answer 15

NADA

Question 16

Describe how endocannbinoids function?

Answer 16

GABAergic transmission (IPSC amplitude) reduced after depolarizing the post-synaptic neuron

A retrograde mechanism whereby post-synapticactivity (depolarization) effects pre-synaptic neurotransmitter release

Question 17

What is endocannbinoids transmission known as?

Answer 17

Depolarisation induced Suppression of inhibition

Question 18

What are the mechanisms of eCB release?

Answer 18

1. Calcium driven eCB Release (CaER)
2. Receptor-driven eCB Release (basal-RER)
3. Calcium-assisted RER (CaRER)

Question 19

Describe calcium drive eCB release;

Answer 19

• Strongpost-synaptic depolarization•e.g. DSI protocol
• Elevated post-synaptic Ca2+inhibits neurotransmitter release
• 2-AG mediated
• Ca2+-dependent synthesizing enzymes
• Blocked by Ca2+chelators

Question 20

Describe receptor driven eCB release;

Answer 20

• StrongG-protein coupled receptors (Gq/11-coupled) activation
• Group I mGluRs(mGluR1 & mGluR5), M1 & M3 muscurinic, oxytocin, orexin, glucocorticoid
• Independent of post-synaptic Ca2+ (basal Ca2+level)
• Ca2+chelatorBATPA resistant
• 2-AG mediated
• PLCβactivated by Gq/11-coupled receptors

Question 21

Describe Ca assisted RER;

Answer 21

•Basal-RER enhanced by elevated post-synaptic Ca2+•PCLβactivity is Ca2+dependent•Synergistic effect of Ca2+and receptor activation on eCBproduction

Question 22

What are the key features of the eCB system?

Answer 22

• Retrograde action
• Endocannabinoids produced on-demand
• Function (primary): Modulation of synaptic transmission

Question 23

Describe how eCB have retrograde action;

Answer 23

• Produced in post-synaptic neuron (various mechanisms…see previous slides)
• Activate CB1 receptor on pre-synaptic terminal

Question 24

Describe how endocannabinoids are produced on demand;

Answer 24

• Not stored in vesicles (like conventional neurotransmitters)
• 2-AG and anandamide are the principle endocannabinoids
• We are also interested in NADA
• Several mechanisms of production (CaER, basal RER, Ca2+assisted RER)

Question 25

Describe CB1 primary function;

Answer 25

• CB1 activation inhibits neurotransmitter release (K+and Ca2+channels involved)
• DSI: Post-synaptic depolarization leads to eCB production/release and inhibition of pre-synaptic neurotransmitter release

Question 26

Describe the symptoms of parkinsons disease;

Answer 26

• Mainly motor-symptoms–Shaking, rigidity, slowness of movement
• Also non-motor symptoms–Loss of sense of smell, disturbed sleep, constipation–Interesting: could precede motor-symptoms

Question 27

Describe the pathology of parkinsons

Answer 27

–Loss of dopamine-producing neuronsin the substantia nigra pars compacta

Loss of dopamine in the striatum

Motor Symptoms

Question 28

What is the current treatment for parkinsons?

Answer 28

L DOPA

Brain adapts though

side effects; •Dyskinesias –involuntary (tics/chorea)

Question 29

Whats an alternative to L DOPA?

Answer 29

•Deep Brain Stimulation (DBS)–Neurosurgical technique–Silences overactive Subthalamic nucleus(STN)–Electrical stimulating electrode placed into the Subthalamic nucleus (or GPe)

Question 30

Could endocannabinoids be a good target for parkinsons treatment?

Answer 30

eCBs indirectly modulate normal synaptic transmission

Dopamine-neuron specific endocannabinoid NADA

Some evidence for improved motor function and effectiveness of L-DOPA –mixed clinical results

CB1 expression is high in the SNc

Question 31

What is the potential for eCB in PD treatment?

Answer 31

1. Slow/stop disease progress

2. Improve existing treatments (L-DOPA)

Question 32

How many marajuana users are dependant?

Answer 32

10%