Glutamate and GABA Flashcards
What are the two main amino acid neurotransmitters in the CNS?
Glutamate (excitatory) and GABA (inhibitory)
How is glutamate synthesised in the CNS?
From glutamine via glial cells or from glucose through the Krebs Cycle.
How is GABA synthesised?
From glutamate using the enzyme glutamic acid decarboxylase (GAD).
What enzyme inactivates GABA?
GABA-transaminase
Name the three ionotropic glutamate receptors
NMDA, AMPA, and Kainate receptors
What is the primary function of ionotropic glutamate receptors?
To mediate excitatory postsynaptic potentials (EPSPs) and fast synaptic excitation.
What are the two main types of GABA receptors?
GABA𝐴 (ionotropic) and GABA𝐵 (metabotropic).
What ion is primarily associated with GABA𝐴 receptor activity?
Chloride ions (Cl⁻).
What is orthosteric modulation?
Direct binding of a neurotransmitter to the active site of a receptor.
What is allosteric modulation?
Binding at a secondary site on a receptor that alters its activity.
Give an example of a drug that acts on GABA𝐴 receptors,
Benzodiazepines (e.g., diazepam).
What role do NMDA receptors play in excitotoxicity?
Overactivation causes excessive Ca²⁺ influx, leading to neuronal damage or death.
Name two clinically useful NMDA receptor agonists.
Ketamine and Memantine.
How do GABA𝐵 receptors modulate neurotransmission?
Presynaptically: Close calcium channels to reduce neurotransmitter release.
Postsynaptically: Open potassium channels to cause slow hyperpolarisation.
What drug targets GABA𝐵 receptors to treat spasticity?
Baclofen
What is the function of Excitatory Amino Acid Transporters (EAATs)?
Reuptake of glutamate into nerve and glial cells to terminate its action.
How do metabotropic glutamate receptors (mGluRs) differ from ionotropic receptors?
mGluRs are G-Protein Coupled Receptors (GPCRs) with slower, neuromodulatory roles via second messengers.
What are the primary second messengers involved in mGluR signalling?
IP₃, cAMP, and Ca²⁺
What percentage of CNS synapses are GABAergic?
Approximately 30%
What distinguishes NMDA receptors from AMPA and Kainate receptors
NMDA receptors are voltage-sensitive and require glycine as a co-agonist for activation.
List the metabotropic glutamate receptors.
Metabotropic Glutamate Receptors (mGluRs): mGluR1 to mGluR8.
