Glutamate and GABA

Question 1

What are the two main amino acid neurotransmitters in the CNS?

Answer 1

Glutamate (excitatory) and GABA (inhibitory)

Question 2

How is glutamate synthesised in the CNS?

Answer 2

From glutamine via glial cells or from glucose through the Krebs Cycle.

Question 3

How is GABA synthesised?

Answer 3

From glutamate using the enzyme glutamic acid decarboxylase (GAD).

Question 4

What enzyme inactivates GABA?

Answer 4

GABA-transaminase

Question 5

Name the three ionotropic glutamate receptors

Answer 5

NMDA, AMPA, and Kainate receptors

Question 6

What is the primary function of ionotropic glutamate receptors?

Answer 6

To mediate excitatory postsynaptic potentials (EPSPs) and fast synaptic excitation.

Question 7

What are the two main types of GABA receptors?

Answer 7

GABA𝐴 (ionotropic) and GABA𝐵 (metabotropic).

Question 8

What ion is primarily associated with GABA𝐴 receptor activity?

Answer 8

Chloride ions (Cl⁻).

Question 9

What is orthosteric modulation?

Answer 9

Direct binding of a neurotransmitter to the active site of a receptor.

Question 10

What is allosteric modulation?

Answer 10

Binding at a secondary site on a receptor that alters its activity.

Question 11

Give an example of a drug that acts on GABA𝐴 receptors,

Answer 11

Benzodiazepines (e.g., diazepam).

Question 12

What role do NMDA receptors play in excitotoxicity?

Answer 12

Overactivation causes excessive Ca²⁺ influx, leading to neuronal damage or death.

Question 13

Name two clinically useful NMDA receptor agonists.

Answer 13

Ketamine and Memantine.

Question 14

How do GABA𝐵 receptors modulate neurotransmission?

Answer 14

Presynaptically: Close calcium channels to reduce neurotransmitter release.
Postsynaptically: Open potassium channels to cause slow hyperpolarisation.

Question 15

What drug targets GABA𝐵 receptors to treat spasticity?

Answer 15

Baclofen

Question 16

What is the function of Excitatory Amino Acid Transporters (EAATs)?

Answer 16

Reuptake of glutamate into nerve and glial cells to terminate its action.

Question 17

How do metabotropic glutamate receptors (mGluRs) differ from ionotropic receptors?

Answer 17

mGluRs are G-Protein Coupled Receptors (GPCRs) with slower, neuromodulatory roles via second messengers.

Question 18

What are the primary second messengers involved in mGluR signalling?

Answer 18

IP₃, cAMP, and Ca²⁺

Question 19

What percentage of CNS synapses are GABAergic?

Answer 19

Approximately 30%

Question 20

What distinguishes NMDA receptors from AMPA and Kainate receptors

Answer 20

NMDA receptors are voltage-sensitive and require glycine as a co-agonist for activation.

Question 21

List the metabotropic glutamate receptors.

Answer 21

Metabotropic Glutamate Receptors (mGluRs): mGluR1 to mGluR8.