On Mon, 05 Jan 2004 00:02:03 GMT, Matthew Kirkcaldie
<Matthew.Kirkcaldie at removethis.newcastle.edu.au> wrote:
>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
>>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
>>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.
It is a good example of the fact that a "negative" signal is just as
good as a "positive" one in communicating information. Stopping doing
something or turning something off is just as important as starting or
turning something on.