Neurotransmitter System II: Glutamate & Glycine Flashcards
What is GABA as a neurotransmitter?
- Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system
- First identified in the mammalian nervous system in 1950
- Around one third of synapses utilise GABA as a neurotransmitter
- It’s most commonly found as a inhibitory neurotransmitter in local circuit interneurons
How is GABA synthesised?
- Glutamate is converted to GABA via a glutamate decarboxylase enzyme. Uses pyridoxal phosphate
- Synthesised in the nerve terminals
- Transported into vesicles by vesicular inhibitory amino acid transporters
Describe the re-uptake of GABA
- Goes from the presynaptic terminal to the post synaptic neuron via GATS
- Neurons and glial contain high affinity Na+ dependent GABA reuptake transporters (GATS)
- Neurons = GAT-1
- Glial cells = GAT-
Describe the degradation of GABA
- GABA converted to succinic semialdehyde via the GABA trans animate enzyme (GABA-T)
- This is then converted to succinic acid via the succinic semialdehyde dehydrogenase enzyme (SSADH)
What are the two broad family of receptors?
- Ligand gated ion channels (ionotrophic)
- G protein coupled receptors (metabotropic)
What type of receptors does GABA bind to?
- Binds to both Ionotropic and metabotropic GABA receptors
- ionotropic receptors = GABAA (LGIC)
- Metabotropic receptors = GABAB (GPCR)
Describe the GABAB receptor
- G protein coupled receptor
- Has a Cysteine rich domain
- Has a 7 transmembrane domain
- Dimers: Heteromers GABAB1 and GABAB2
- Watch lecture for this bit
What can inhibitory neurotransmitters cause?
- Can cause neuronal membrane hyperpolarisation
- Which is the displacement of the membrane potential towards a more negative value
- Watch lecture
What is the cerebellum as a part of the brain?
- A prominent hind structure
- Accounts for approximately 10% of the human brains volume
What is the function of the cerebellum?
- Detects differences in Motor error between an intended movement and the actual movement
- Aids the motor cortex to produce precise and coordinated movement
- Doesn’t initiate movement
Is the function of the cerebellum conserved?
- Its been shown that the cerebellum is important in synchronisation of movement with musical rhythm
- This could be widespread across the animal kingdom
What are Purkinje cells?
A class of GABAergic neurons that comprise the principle projection neurons of the cerebellar cortex
Describe the structure of purkinje cells
Have elaborate dendritic trees that receive convergent input from cells in the molecular layer
What is the function of purkinje cells?
- They send GABAergic projections to deep cerebellar neurons
- Purkinje cell output to the deep cerebellar neurons which generates an error connection signal that can modify movements
- This provides the basis of real time control of precise and synchronous movement
How is GABA and glutamate balanced in the brain?
- GABA and glutamate are the major neurotransmitters in the brain
- Both work together to control the brains overall level of excitation
- In one step, the major neurotransmitter is converted into the other major neurotransmitter in the brain
