Download 5-2_NeurotransmRelease_BenseM

Bense Márk
Neurobiology Seminar
2016/17/1.
The spontaneous and action potential
generated transmitter release
Neurotransmitter:
Neurotransmitters are endogenous bioactive substances, synthesized by
neurons, and that are released from the cells, act via specific receptors, coupled to the
membrane of postsynaptic target, structure and modify the electric and metabolic conditions
of the affected cells.
Main stages of neurotransmitter release:
1. When the action potential comes down the axon and reaches the axon
terminal, the membrane potential will change
2. This change will open voltage-gated Ca2+ channels, that let the Ca2+ flow in
3. This transport happens because of the difference in the ion concentration on
the two sides of the axon terminal (outside higher than on the inside)
4. Inside the axon terminal the increased Ca2+ concentration causes changes to
proteins on the synaptic vesicles and the pre-synaptic membrane, so
eventually they interact and fuse with each other
5. The inside of the vesicles are now in direct contact with the outside of the
axon terminal
6. By diffusion, neurotransmitters are able to cross the synaptic cleft and
attach to the receptors located at the surface of the pos-synaptic membrane
of the target cell
Quantal neurotransmitter release:
1. Neurotransmitters are synthesized in the axon terminal and are stored in
vesicles
2. These neurotransmitter-filled vesicles are called quanta
3. Quantal vesicles release the transmitters into the synapse after the binding of
its and the membrane’s layers
4. This process may randomly happen and cause a subsequent MEPP
(miniature end plate potential – the smallest amount of stimulation that one
neuron can send to another)
5. These diffusions are not the result of any signaling pathway
References:
 Lodish, H.; Berk, A.; Zipursky, S.L. (2000). Molecular Cell Biology
 Cherry, Kendra. "What is a Neurotransmitter?" (2014)
 https://en.wikipedia.org/wiki/Neurotransmitter
 Rapport, Richard L. (2005). Nerve Endings: The Discovery of the Synapse
 Relevant lecture slides (“Release of neurotransmitters” – 6. 8. 20.)
 http://www.williams.edu/imput/synapse/pages/I.html