Weighting of synaptic response - Next Epsiode
bill at nsma.arizona.edu
Sat Aug 31 18:32:21 EST 1996
rreich at shell01.ozemail.com.au (Joshua Reich) writes:
> As far as i see it, there are 4 possible ways of strengthening a
> transmission, could anyone out there either confirm or deny any
> of my guesses.
> 1) More neurotransmitter is released by the presynaptic cell.
> 2) Less enzymes (ie. acetylcholinesterase) present in synapse.
> 3) More receptors on the postsynaptic neuron.
> 4) More ion channels (or less depending on particular ion in
> question) on post-syn. cell.
All of these mechanisms are possible, and there are some others as
well. 5) The affinity of the receptors for the neurotransmitter can
be modified. (For example, benzodiazepine tranquilizers work by
increasing the affinity of the GABA receptor for GABA, thereby
increasing the effective strength of GABA synapses.) 6) Second
messenger systems can influence the amount of current that flows
through an ion channel after it has been activated. 7) Interactions
with neighboring synapses on the postsynaptic cell can change the
effective strength of a synapse. The most striking example is the
fact that many excitatory synapses occur on dendritic spines, and
often there are inhibitory synapses on the necks of the same spines.
Activation of the inhibitory synapse will reduce the effective
strength of the excitatory synapse, without having much other effect.
This is by no means an exhaustive list.
> A) What controls the factor. Say that the effect is primarly due
> to a reduction of acetylcholinesterase, what reduces the presence
> of this. Is it under some sort of hormonal control, or what?
This is a very active area of investigation. The brain has many
mechanisms for controlling synaptic strength, on many different time
scales. We are only beginning to make sense of them.
> B) How hard would it be for me (as a first year student - a keen
> one at that) to practically research this in a lab ?
Not clear what you're asking. If you're talking about doing research
on your own, give up the idea. You really need to find a mentor to
learn how to do any sort of serious wet neuroscience research. If you
mean, how hard is it to find a lab working on synaptic control
mechanisms, the answer is that there are hundreds of them, scattered
all around the world. Many of them would be eager to find some use
for a serious, hard-working undergraduate.
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