I appreciate that chemical synapses can be either inhibitory (Gray Type I) or
excitatory (Type II) and that studies on neuromuscular systems indicate that
during the course of development immature synapses preceed mature synapses.
However, how is the type of synapse determined ? I've not found anything
specific in the literature I've read so I've got a few questions.
1. Is type 'genetically predetermined' so that say a postsynaptic cell always
makes excitatory connections with whatever it contacts ? Or similarly is type
defined only by the pre-synaptic cell ?
2. Is it just the result of where the axon actually contacts its target cell ?
Kandel (Essentials in Neural Science and Behaviour 95) says that type can be
determined by whether the synapse is axo-dendritic, axo-axonic or axo-somatic.
Is this the only way to tell ?
3. Does electrical activity / usage determine type ? I'm envisaging that
immature synapses have a generic morphology which through the 'tuning' of the
ion channels, gives rise to the different types.
Any comments would be most useful together with some pointers towards the right
kind of papers I should be reading.
AliStair G. Rust
<a.g.rust at herts.ac.uk>
Division of Computer Science,
University of Hertfordshire, Hatfield, Herts, AL10 9AB, UK