W8L2 - Glutamate and GABA Flashcards
List down some properties of Glutamate and Gaba: (1) Evolution (2) Commonality (3) “True”
Glutamate and GABA
- Believed to be the first to evolve and are found in very simple organisms
- Most common neurotransmitters in the CNS
- “True” neurotransmitters – directly affecting the likelihood of the post-synaptic neuron firing
What is the main excitatory NT? What does the excitation NT do in terms of firing
Glutamate
Increase likelihood of post-synaptic neuron firing
How many of the brain synapse release glutamate
Estimated over half of all brain synapses.
What is the acid associated with glutamate
Glutamic Acid
Must glutamate be synthesized? Why?
- Glutamate = Glutamic Acid
- Glutamate is an amino acid that acts as a neurotransmitter in its “original” form but this amino acid does not pass the blood brain barrier so it still needs to be synthesized in the brain
- Glutamate is synthesized from glutamine which is released by cells neighbouring the neurons
Glutamate > Glutamine >(Synthesised by neighbouring cells) > Glutamate
Where is glutamate found
In most long projection neurons throughout cortex
What are the connection points like for excitatory connections”. Do they have general functions?
“Point-to-Point”. Direct.
No, there are many region-specific functions (e.g. vision)
How many types of glutamate receptors are here?
- 3 Ion channels
- NMDA Receptor
- AMPA Receptor
- Kainate Receptor
- 1 G-protein coupled receptors
- Metabotropic Glutamate Receptor
NMDA Receptor: How many binding sites are there. What are some conditions for glutamate to be attached
6 Different Binding Sites.
- Glycine Molecule attached
- Magnesium ion not bound
- Or else it won’t open
Other binding cites modulate receptor function.
What are some drugs discussed in Week 8 Lecture 2 that affects NMDA. What do they have in common.
Alcohol, PCP, Ketamine
- NMDA antagonists (inhibit)
- But they all have different impacts on the mind
How does alcohol related to NMDA receptor. What does this explain
- NMDA antagonist (inhibit)
- Reduce glutamate
- GABA agnoist (excite)
- Increase GABA
- Explains general sedative effects and brain inhibition
What does PCP and Ketamine cause. Are they safe?
PCP = “Angel Dust”
Ketamine = “Special K”
- PCP and Ketamine are NMDA antagonists (Reduce glutamate)
-
Dissociative hallucinations
- Feel disconnected rather than perceiving visions
- Risk of suicidal behaviour
- Though Ketamine is very safe
-
Dissociative hallucinations
What is the association between glutamate and psychosis?
What is psychosis?
What changes are there in individuals with psychosis?
- Some have suggested a link between glutamate and psychosis but it is controversial and likely to involve others NTs like DA.
- Psychosis
- Symptom cluster, not diagnosis
- SZ = 1% (Diagnosis)
- Psychosis = 3% (Symptom Cluster)
- Widespread disruption & lack of coherent integration of sensory information
- No major structural impairment in psychosis
- Likely reflect chemical inbalances
- Symptom cluster, not diagnosis
Genetic studies and psychosis. What is the role of NMDA? Conclusion?
Genetic studies on Psychosis
- NMDA receptor activity
- Critical for learning, memory, perception and synaptic plasticity in general.
- Genetic studies identify NMDA receptor genes as likely being relevant in schizophrenia, but also relevant to general function and IQ
- Large number of genes that all may each contribute to a small amount of risk for psychosis.
- Picture remains unclear and may simply reflect altered synaptic activity in psychosis
What is GABA and what does it do in to the post-synaptic neuron?
Main inhibitory NT - Decreasing likelihood of the post-synaptic neuron firing
Where is GABA found
In short local neurons, forming a dense web around and between excitatory neurons
How does GABA help in neural tuning. Are they perfect?
- Delicate coordination of neurons to signal very specific information
- “Keeping signal sharp”
- Selective, not perfect
- Reduce likelihood of neurons firing for non-preferred stimulus (Dosen’t stop firing for non-preferred stimulus)
- Explains tuning curve
What is GABA produced from. Can it convert to Glutamate?
Glutamic Acid (Same as glutamate)
Glutamate is converted into GABA & GABA can be converted back to Glutamate
Are Glutamate and GABA released from the same neurons?
Made from same amino acid, but not released from same neurons
How many types of GABA receptors are there
- 1 Ion
- GABAa
- 1 G-Protein
- GABAb
What is the prevalance of seizures. What are seizures? How does GABA explain epilepsy or seizures?
- Relatively common (400,000) in Australia
- Seizures
- Sudden excessive activity of neurons
- (Can cause muscle convulsion but not always)
- Epilepsy (Neurological disorder characterised by seizures) are caused by abnormalities of GABA neurons and/or in GABA receptors
What are generalized seizures
Involving whole brain
What are partial seizures. And what are simple and partial seizures?
Restricted to small area of brain
- Simple
- Can cause changes in consciousness (altered sensory, autonomic responses etc)
- Not loss of consciousness
- Complex
- Loss of consciousness
Explain the study on high fever and vaccinations.
High fever and Vaccinations.
- Vaccinations cause high fevers in some children and the fevers can trigger the first epileptic event
- Some children with epilepsy genes without vaccinations still ended up getting epilepsy
- Some children with epilepsy gene had seizures before vaccinations
In genetic studies, in seizures, which kind of receptors have GABA been most identified with. What is the problem.
- Majority of genes so far control ion channels, BUT
- Most seizures are not genetic and instead are due to abnormal brain tissue, requiring surgery
Are Ion Channels more selective than G-Protein Coupled? What are some similarities and differences in relation to (1) Length and action; (2) Systems
No. G Protein-coupled receptors and ion chanels are equally selective (activated by more neurotransmitters)
Length and Action
- Both ion channels and G Protein-coupled receptors span the cell membrane
- G Protein-coupled receptors have a relatively long action compared to ion channels
Influence
- Only G-Protein coupled receptors can influence metabolic processes within a cell via second messenger systems
