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Axon collaterals ?

Matthew Kirkcaldie Matthew.Kirkcaldie at removethis.newcastle.edu.au
Sun Jan 4 19:02:03 EST 2004


In article <hvn9vv0ljsu5b4c2vmcro9rnjvltojrfst at 4ax.com>,
 r norman <rsn_ at _comcast.net> wrote:

> On Fri, 02 Jan 2004 12:17:46 +1100, Matthew Kirkcaldie
> <Matthew.Kirkcaldie at removethis.newcastle.edu.au> wrote:
> 
> >In article <erk3uvs9tqjkgkg2fklq2o4fls4u05ne2s at 4ax.com>,
> > r norman <rsn_ at _comcast.net> wrote:
> >
> >> Yes.  Even glutamate has both in the retina.  I misspoke
> >> about "all" the known glutamate receptors.  Glutamate is
> >> "ordinarily" excitatory in the CNS.
> >
> >What's the inhibitory glutamate receptor in the retina?
> >
> >While we're on the subject, it's worth remembering that GABA is 
> >excitatory in the immature CNS.
> >
> 
> The synapse from receptor to bipolar is supposed to be glutamatergic,
> even though "on" and "off" bipolars have opposite responses.  Here is
> a reference

...
[skip many]

Thank you!  Sigh, more reading.

For others following the discussion, the other incredible thing in the 
retina is that signalling is done by switching OFF the stream of 
transmitter coming from the rods and the cones.  So a detectable burst 
of light produces a temporary stop in the outflow of glutamate, and this 
pause in secretion is what we actually detect as the basis for visual 
stimuli!

Show you how quickly the glial cells scavenge the glutamate from the 
cleft - and why vision is actually the slowest of the senses in terms of 
the briefest detectable stimulus.

         Matthew.

PS: please feel free to correct or amplify - I'm just a spectator in 
visual neuroscience.



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