Lecture 2 Glutamate & GABA Flashcards
(15 cards)
What are the primary excitatory and inhibitory neurotransmitters in the brain?
Glutamate (primary excitatory)
GABA (primary inhibitory).
Why are glutamate and GABA considered “true” neurotransmitters?
“They directly affect the likelihood of the post-synaptic neuron firing (glutamate increases firing, GABA decreases it).”
How is glutamate synthesized in the brain?
- Synthesized from glutamine (released by neighboring glial cells)
- Cannot cross the blood-brain barrier (BBB), so must be produced locally
Name the 4 major types of glutamate receptors.
3 are Ionotropic: NMDA, AMPA, Kainate.
1 is G-protein-coupled / Metabotropic: mGluR
What makes the NMDA receptor unique?
particularly complex!
* It has at least 6 different binding sites
o For example, it only works if
o there is also a glycine (甘氨酸) molecule (another amino acid) attached
o if magnesium ion is NOT bound to inside
- The other binding cites modulate receptor function.
How do alcohol, ketamine, and PCP affect NMDA receptors?
All are NMDA antagonists (reduce excitatory function).
Alcohol: Sedation & memory impairment
Ketamine/PCP: Dissociative hallucinations
Why is ketamine used to treat depression?
- Effective for weeks, but relaps after
- relatively Safe
How might glutamate dysfunction contribute to psychosis?
- NMDA antagonists can cause positvie and negative synptoms of psychosis
What is GABA’s role in the brain?
Primary inhibitory neurotransmitter.
Decrease post-synaptic neuronal firing (e.g., seizures)
- Most short local neurons are inhibitory, so they form a dense web around and between the excitatory neurons (~20% of cerebral cortex interneurons) –> Inhibitory networks reduce the likelihood neurons fire for their non-preferred stimulus
How is GABA synthesized?
“Produced from glutamate via enzymatic conversion (GAD enzyme).”
Name the two GABA receptor types and their mechanisms.
- GABA_A: Ion channel (target of alcohol, benzodiazepines).
- GABA_B: G-protein-coupled.
What happens when GABA function is impaired?
“Seizures (uncontrolled neuronal firing due to lack of inhibition).”
What are generalized vs. partial seizures?
Generalized: Whole brain (e.g., tonic-clonic)
Partial: small part of brain, often due to injury or abnomal development(simple = no consciousness loss; complex = loss of consciousness).”
Why are benzodiazepines (e.g., Valium) used in alcohol withdrawal?
They enhance GABA activity, counteracting excessive glutamate excitation that causes seizures.
Key clinical point about glutamate/GABA balance?
Disruption (e.g., excess glutamate or low GABA) leads to seizures, psychosis, or neurotoxicity.
