changes in synaptic number

Thomas Chimento chimento at ursa.arc.nasa.gov
Wed Dec 28 12:24:27 EST 1994


I have been looking for references on changes in the number of synaptic
connections resulting from an alteration in the input or environment of an
organism. I have done all the Medline searches under synaptic plasticity
and read numerous review articles on synapses, but I am unable to find an
example of anatomical, quantitative  changes in the number of synaptic
sites anywhere in the nervous system caused by changing the input to that
part of the nervous system. I am not toaking about dendritic spine numbers,
but the synaptic sites within existing neurons. 

The reason I am searching for this information is that our experiments in
the vestibular endorgan have demonstrated a change in the number of
synaptic sites within hair cells when the gravitational environment is
altered. In a hypergravity environment produced on a 24' centrifuge (2-g)
the number of synaptic sites decreases whereas an opposite effect occurs
when the animals (rats) are placed in microgravity aboard the Space
Shuttle. I am hesitant to state that this is the only such case
demonstrated, but have not been able to find any others. Any help would be
greatly appreciated. Suggestions of key words for a search, books,
articles, or specific investigators names all would be very helpful. 
Thanks

Thomas

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