Neurotransmission
Another aspect of neuronal survival is that to survive a neuron must display synaptic activity, this is not needed at first but later on in development after neuronal maturation. Conversely, too much electrical activity can kill a neuron.
The reason for this is not entirely clear. It could be;
- Neurotrophic factors are released at the synapse.
- Neurotransmitters themselves act as a neurotrophic factor.
The NMDA receptor is a glutamate binding ion channel that allows Ca2+ and Na+ into the cell and K+ out of it. It is known to be involved in increasing neuronal survival at synapses in the hippocampus.
When inactive a Mg2+ ion sits in the ion channel, this must first be removed by membrane depolarisation before ligand binding can have an effect. Therefore, NMDA receptors require stimuli from two different sources to activate.
This receptor is largely implicated in learning and memory, and has been shown to improve neuron survival by increasing calcium levels when inside a synapse. Conversely it will increase neuron death if located outside of a synapse.
Neuronal Calcium Sensor 1 (NCS 1)
This protein senses levels of calcium, it has many functions, one of is enhancing neuronal survival.
NCS 1 is highly expressed in the brain and has a high affinity for calcium.
Image from Wkimedia Commons https://commons.wikimedia.org/wiki/File:NMDA_receptor.jpg, author: Blanca Piedrafita, licence: Creative Commons Attribution ShareAlike 2.5
