Axon collaterals ?
r norman
rsn_ at _comcast.net
Thu Jan 1 22:35:15 EST 2004
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
Grant GB, Dowling JE
A glutamate-activated chloride current in cone-driven ON
bipolar cells of the white perch retina.
J Neurosci. 1995 May;15(5 Pt 2):3852-62
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7538566&dopt=Abstract
and
Grant GB, Dowling JE.
On bipolar cell responses in the teleost retina are generated by
two distinct mechanisms.
J Neurophysiol. 1996 Dec;76(6):3842-9
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8985882&dopt=Abstract
I learned of it from indirect souces like a Neuro text (which one I
don't remember) or
How the Retina Works
American Scientist 91:28 (2003)
http://www.americanscientist.org/template/AssetDetail/assetid/16218/page/3
However, the situation may be complicated -- the glutamate response
may be indirect and actually mediated by GABA -- see
Hartveit E.
Membrane currents evoked by ionotropic glutamate receptor
agonists in rod bipolar cells in the rat retinal slice preparation.
J Neurophysiol. 1996 Jul;76(1):401-22.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8836233&dopt=Abstract
Invertebrate are more clearcut -- there are distinct inhibitory
glutamate receptors as described in
Cleland TA.
Inhibitory glutamate receptor channels.
Mol Neurobiol. 1996 Oct;13(2):97-136
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8938647&dopt=Abstract
or
Thomas A. Cleland and Allen I. Selverston
Dopaminergic Modulation of Inhibitory Glutamate Receptors in
the Lobster Stomatogastric Ganglion
J Neurophysiol 78: 3450-3452, 1997
http://jn.physiology.org/cgi/content/abstract/78/6/3450
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