Neurotransmitters Flashcards
What is synaptic transmission?
Information transfer across the synapse that requires the release of neurotransmitters and their interaction with postsynaptic receptors
What are the main features of synaptic transmission?
Rapid timescale Diversity Adaptability Plasticity Learning and memory
What are the steps in transmission of information?
Information reception
Integration
Rapid transmission
What are synapses?
Presynaptic nerve terminal
Synaptic cleft (20-100nm)
Postsynaptic region
Specialised structures to which neurotransmission is restricted to
What are the 3 stages of synaptic transmission?
Biosynthesis- packaging and release of neurotransmitters
Receptor action
Inactivation
Give examples of neurotransmitters
Amino acids e.g. glutamate and glycine
Amines e.g, noradrenaline and dopamine
Neuropeptides e.g. opioid peptides
How does the concentrations of neurotransmitters vary?
mM to nM
How does the time scale of neurotransmission vary?
microseconds - milliseconds
Rapid or slower effects
Summarise the action of neurotransmission
Neurones receive multiple transmitter influences which are integrated to produce a wide range of functional responses
What are the steps of activation a CNS synapse?
Arrival of action potential Causes VGCC's to open Rapid influx of calcium Vesicle fusion and exocytosis Release of transmitter Moves across synaptic cleft Activates receptor on postsynaptic membrane
How do rapid release rates occur?
Vesicles are filled and docked in the synaptic zone
Special proteins enable fusion and exocytosis
What are vesicular proteins targets for?
Neurotoxins
Give some examples of neurotoxins
Alpha latroxin (from black widow) Simulates transmitter release to depletion
Tetanus toxin, C tetani causes paralysis
C botulinum causes flaccid paralysis
What are the two main classes of receptors?
Ion channel receptors- fast response
G-protein couples reactors- slow response
Give examples of when ion channel receptors are used
CNS- Glutamtes binds to GABA
NMJ- Ach at nicotinic recpeptors
Give examples of when G-protein coupled receptors are used
ACh at muscarinic receptors
What are the main features of ion channel-linked receptors
Rapid activation
Rapid info flow
Multiple subunit combinations- distinctly functional properties
What are the two main types of glutamate receptors?
AMPA- fast excitatory synapses, linked to Na channels
NMDA- slow excitatory synapses
What are the steps of on glutamine production?
Glutamate synthesised from glucose via TCA and transamination
Glutamate reversibly binds post-synaptic receptors
Rapid uptake of glutamate by excitatory amino acid transporters
Glutamte enzymatically modified by glutamine synthetase to glutamine in glial cell
What can seizures be caused by?
Abnormal cell firing causes seizures associated with excess glutamate in the synapse
What’s the deal with epilepsy?
One of most common neurological conditions affecting 50 million people worldwide
Recurrent seizures due to abnormal neuronal excitability
Disease can be disabling
What occurs at a GABAgernic synapse?
GABA formed by decarboxylation of glutamate by glutamic acid decarboxylase
GABA reversibly binds post-synaptic receptors
Rapid uptakes of GABA by GABA transporters
GABA enzymatically modified by GABA-transaminase to succinate semialdehyde in glial cell
What is the structure of GABA receptor?
Pentameric organisation
Pharmacologically important binding domains
What drugs facilitate GABA transmission?
Antiepileptic
Anxiolytic
Sedative
Muscle relaxant
