Neurotransmitters Flashcards
What makes a neurotransmitter a neurotransmitter?
A. The chemical must exist (made and stored) in presynaptic cells (stored in terminals)
B.The chemical must be released from presynaptic terminals on action potential
C. Released chemical must bind to receptors and cause a biological effect
D. There must be a mechanism to inactivate or metabolise the chemical
E. The chemical should have the same biological effect if artificially applied to synapse
Where do neurotransmitters come from?
Peptides (made in the soma)
* Precursor peptide (small protein) synthesised in rough ER
* Cleaved in Golgi apparatus to active neurotransmitter
* Secretory vesicles bud off from Golgi apparatus
* Secretory granules (large vesicles, 100 nm) transported to terminal and stored
Monoamines, Amino Acids & Acetylcholine (made in the pre-synaptic terminal) Don’t have to travel
* Precursor molecule (from diet) sythesised to neurotransmitter
* Transported to synaptic vesicle (50 nm) and stored
What is the main Difference between Peptides & Monoamines, Amino Acids or Acetylcholine neurotransmitters?
- Peptide neurotransmitters are made in the soma and transported in secretory granules to the terminal
- Monoamines, amino acids and acetylcholine are made from precursor molecules in the terminal and are transported into synaptic vesicles
What are the major roles of amino acid neurotransmitters?
Glutamate: Major Excitatory NT, Learning & Memory, Neuroplasticity, Excitotoxicity
GABA: Major inhibitory NT, Modulator of many processes
Where are the cell bodies of neurons that release amino acid neurotransmitters and where do they project?
Glutamate: thal and subthal, project to various places in cerebral cortex and basal ganglia
GABA: in hippo, accumbens and midbrain and project to cortex and cerebellum and olfact bulb
GABA is also in interneurons
What are interneurons?
Interneurons are small neurons retained in the one brain area GABA or Acetylcholine are commonly in interneurons
How are amino acid neurotransmitters metabolised?
2 ways (presyn + glial cell) to make sure that the cell env doesnt become too toxic bc of too much NT outside the cell
GABA transaminase breaks down GABA in the presynaptic cell and glial cells
Glutamate is neurotoxic (kills neurons) in high amounts - glial cells work to reduce toxic levels
What are the major roles of ACh? (4)
NTs are associated with a wide variety of imp fctions
This is why any NT dysfction can be very problematic
for everyday fction
Memory, Perceptual Learning, Movement and REM Sleep
Where are the Acetylcholine cell bodies and where do they project?
Nucleus basalis and project to
frontal and parietal cortex
They’re also in sub nigra and go to thal
Septohippocampal pathway projects
to hippo
How is ACh metabolised?
Acetylcholine is broken down by Acetylcholine esterase (AChE) into choline and acetic acid
ACh metabolism occurs in the synaptic cleft
Choline is then transported into the presynaptic cell for re-use
Many insecticides or nerve gases inhibit AChE, enhances ACh transmission at muscle and heart, death usually by respiratory paralysis
Outside agents can interfere with NTs to affect someones fction and overall health
What is ACh’s life cycle?
More choline detected in the synaptic cleft = reduces ACh production
Rate limiting step is choline in synapse - inversely related (negative feedback)
What are the major roles of monoamines?
- Dopamine: Short term memory, Strategy & planning, Reward and Movement
- Serotonin: Cognition, Emotion and Reward
- Noradrenaline: Attention, Flight/Fight and Sleep
Where are the Dopamine and Noradrenaline cell bodies and where do they project?
- Noradrenaline: In the LC and caudal raphe, project to cerebellum and cortex
- Dopamine: In SN and VTA, prooject to frontal cortex and midbrain
Where are the Serotonin cell bodies and where do they project?
In raphe (rostral, caudal and dorsal) that roject to cortex and cerebellum
NTs are associated with mvmt
and higher cog fctions bc of
where they project
How are monoamines metabolised?
Monoamines deactivated by Monoamine Oxidase (MAO) or repackaged into vesicles in the presynaptic cell
MAO inhibitors used as antidepressants
Each monoamine has its OWN transporter (You can selectively target these transporters):
Dopamine = DAT Noradrenaline = NET
Serotonin = SERT
They are each taken up into their own cell and metabolised or repackaged into vesicles
