Neuroscience 5 - Neurotransmitters

Question 1

What are the 3 classes of neurotransmitter?

Answer 1

1. Amino Acids (GABA)
2. Amines (noradrenaline, dopamine)
3. Neuropeptides (opioid peptides)

Question 2

Explain the mechanism of neurotransmission step by step.

Answer 2

1. Action potential comes and Ca2+ channels in membrane open.
2. Influx of Ca2+ into the cell.
3. Ca2+ bind to vesicles containing neurotransmitter and triggers their release into synapse.
4. Neurotransmitter diffuses across synapse to post synaptic membrane and binds to receptors.
5. Na+ moves into the cell and starts action potential.
6. Neurotransmitter (amino acid) is then removed from synapse by transporter proteins and packaged back into vesicles.
7. NA+ K+ pump brings back the resting membrane potential.

Question 3

What is Docking?

Answer 3

1. Vesicles and the cell membrane at the active zone have alpha helical structures.
2. These structures interact with each other to form a super helix that forms a stable complex of the vesicle at the synapse.

Question 4

How does Ca2+ activate the release of neurotransmitter?

Answer 4

Ca2+ channels at the active zone allow Ca2+ in when there is an action potential. Ca2+ diffuses into the cell and binds to Ca2+ sensitive receptors on the vesicle. The stable complex of the vesicle and the membrane undergo a change to release the neurotransmitter.

Question 5

What are the 2 types of neurotransmitter receptors?

Answer 5

1. Ion Channel Receptor - GABA and Glutamate

2. G-protein coupled receptor - Dopamine and Noradrenaline.

Question 6

What is an example of an inhibitory receptor and how does it work?

Answer 6

GABA receptors are an example of an inhibitory receptor. It allows the diffusion of Cl- into the cell, which causes hyperpolarisation.

Question 7

What is an example of an excitatory receptor and how does it work?

Answer 7

Glutamate receptors are an example of an excitatory receptor. It allows the diffusion of Na+ into the cell, which causes depolarisation.

Question 8

What are the 2 types of Glutamate receptors?

Answer 8

1. AMPA - allows Na+ in

2. NMDA - allows Na+ and Ca2+, but needs 2 inputs (membrane depolarisation + glutamate must bind)

Question 9

How is glutamate formed?

Answer 9

Glycolysis and Krebs cycle and then transamination of alpha-ketoglutarate.

Question 10

How is glutamate removed from the synapse?

Answer 10

Removed via transporters on the pre-synaptic membrane and glial cell. EAAT2 is the main transporter found on the glial cell. Glutamate is then inactivated by glutamine synthetase to make glutamine.

Question 11

How is GABA synthetised?

Answer 11

Synthetised by GAD (vitamin B6) using glutamate.

Question 12

How is GABA removed from the synapse?

Answer 12

Transporters on the pre-synaptic membrane and glial cell remove GABA. It is then inactivated by GABA transaminase to succinate semialdehyde - this goes into the TCA cycle.

Question 13

Why is the GABA receptor important for treating epilepsy?

Answer 13

You can produce anti-epileptic drugs that interact with the GABA receptor. There are binding sites for benzodiazepines and barbiturates that facilitate the diffusion of Cl- into the cell.

Question 14

What are 4 types of drugs that facilitate GABA transmission?

Answer 14

1. Anti-epileptic
2. Anxiolytic
3. Sedative
4. Muscle relaxant