Neurotransmitters Flashcards

1
Q

What is synaptic transmission?

A
Information transfer across the synapse requires release of neurotransmitters and their interaction with postsynaptic receptors
•Rapid timescale
•Diversity
•Adaptability
•Plasticity
•Learning and memory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is basic process of synaptic transmission?

A
  1. Transmitter released from 1st cell
  2. Synaptic activation of 2nd cell
  3. Signal integration and conduction by 2nd cell
  4. Signal transmitted to effectors or subsequent neurones
    Electrical, chemical, electrical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the structure of a neurone?

A

Each neurone may receive and make several hundred or thousand synapses
Communication between cells requires neurotransmitter release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe neurotransmitters

A
  • Enormous diversity in variety of transmitters and their receptors including Amino acids (e.g. glutamate, gamma amino butyric acid [GABA], glycine [gly]), amines (e.g. noradrenaline [NA] and dopamine [DA]) and neuropeptides (e.g. opioid peptides)
  • Vary in abundance from mM to nM CNS tissue concentrations
  • May mediate rapid (µs - ms) or slower effects (secs)
  • Neurons receive multiple transmitter influences which are integrated to produce diverse functional responses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are essential components for synaptic transmission?

A
  • Restricted to synapses
  • Calcium essential (transmitter release required increase in intracellular Ca2+ 200 micro M
  • Transmission is fast - within ms molecules perSV
  • Synaptic vesicles (SVs) provide het source of neurotransmitter (4,000-10,000 molecules per SV)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Summarise neurotransmitter release

A
Activation of transmitter release is calcium dependent and requires RAPID transduction 
1. Membrane depolarisation 
2. Ca2+ channels open 
3. Ca2+ influx 
4. Vesicle fusion 
5. Vesicle exocytosis 
6. Transmitter relase 
Electrochemical transduction from 2-8 200 mu secs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How to rapid release rates occur?

A
  • Synaptic vesicles are filled with neurotransmitter (T) and disked in the synaptic zone
  • Special proteins on the vesicle and pre-synaptic membrane enable fusion and exocytosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe some neurotransmitters

A
  • Vesicular proteins are targets for neurotoxins
  • Alpha latrotoxin (from black widow spider) stimulates transmitter release to depletion
  • Zn2+-dependent endopeptidases inhibit transmitter release
  • Tetanus toxin C tetani causes paralysis
  • Botulinum toxin C botulinum causes flaccid paralysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Recap transmitter release requirements

A
  1. Calcium dependent (Ca2+)
  2. Transmitter-containing vesicles to be docked on the pre-synaptic membrane
  3. Protein complex formation between vesicle membrane and cytoplasmic proteins to enable both vesicle docking and a rapid response to Ca2+ entry leading to membrane fusion and exocytosis
  4. ATP and vesicle recycling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is an ion channel receptor?

A

-fast response (msecs), medicate all fast excitatory and inhibitory transmission

CNS: Glutamate,
Gamma amino butyric acid (GABA)
NMJ: Acetylcholine (ACh) at nicotinic receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a G-protein coupled receptor?

A

slow response (secs/mins), Effectors may be enzymes (adenyl cyclase, phospholipase C, cGMP-PDE) or channels (e.g. Ca2+ or K+)

CNS and PNS: ACh at muscarinic receptors, dopamine (DA), noradrenaline (NA), serotonin (5HT) and neuropeptides (e.g. enkephalin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe ion channel linked receptors

A
  • Rapid activation µ to msec
  • Rapid information flow
Multiple subunit combinations-distinct functional properties

-Nicotinic cholinergic receptors (nAChR), glutamate (GluR), GABA (GABAR), Glycine (GlyR) receptors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is AMPA (glutamate receptor)?

A
  1. AMPA RECEPTORS
    Alpha amino-3-hydroxy-5-methyl-4-isoxazole propionic acid
    Majority of FAST excitatory synapses

Rapid onset, offset and desensitisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is NMDA (glutamate receptor)?

A
  1. NMDA RECEPTORS
    N-methyl-D aspartate

Slow component of excitatory transmission
Serve as coincidence detectors which underlie learning mechanisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens in an excitatory CNS synapse?

A
  1. Glutamate synthesised from glucose via TCA cycle and transamination
  2. Glutamate reversibly bonds to post-synaptic receptors (linked to ion channels)
  3. Rapid uptake of glutamate by excitatory amino acid transporters (EAATs)
  4. Glutamate enzymatically modified by glutamine synthesise to glutamine synthesise in glutamine in gill cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are seizures?

A
  • Electroencephalography (EEG) measures electrical activity in the brain
  • Abnormal cell firing leads to seizures associated with excess GLUTAMATE in the synapse
  • Usually managed with GABA
17
Q

Describe an inhibitory CNS synapse

A
  1. GABA formed by decarboxylation of glutamate by glutamic acid decarboxylase (GAD)
  2. GABA reversibly binds to post-synaptic receptors (linked to ion channels)
  3. Rapid uptake of glutamate by GABA transporters (GATs)
  4. GABA enzymatically modified by GABA-transaminase to succinate semialdheyde in glial cell
18
Q

What is the structure of the GABA receptor?

A

Pentameric organisation of the GABA receptor and pharmacologically important binding domains

19
Q

What are drugs facilitating GABA transmission?

A
  • Antiepileptic
  • Anxiolytic
  • Sedative
  • Muscle relaxant