Conditioning?

Lisa A Romano v055pcqa at ubvms.cc.buffalo.edu
Wed Nov 3 10:49:00 EST 1993


In article <1993Nov2.195859.20323 at oucsace.cs.ohiou.edu>, bwhite at oucsace.cs.ohiou.edu (William E. White ) writes...
>Forgive me, but I have several questions here; I'm sure my knowledge on this
>subject is as out-of-date as the texts here at our library (1989 and older),
>and I'm trying to get the background to do graduate work in cognitive AI
>and biologically based neural nets.
> 
>In article <2a9spl$6qe at news.u.washington.edu> wcalvin at stein1.u.washington.edu (William Calvin) writes:
>>      The other type of glutamate channel -- named "NMDA" for
>>reasons that are arcane and irrelevant -- allows some calcium ions to
non-NMDA channels also have the potential of being  Ca permeable, specifically,
the GluR2 subunit is impermeable to Ca and confers this to other subunits 
when they are coexpressed.  But when other subunits are expressed without 
GluR2 present, the non-NMDA channels are permeable to Ca.
>>enter the dendrite as well.
  But what's really extraordinary about the
>>NMDA channel is that it won't open unless it has two signals at the
>>same time:  it takes both the right voltage and the right neurotransmitter
>>to open up.  That's like a locked entrance door that requires a valid
>>keycard to be stuck in a slot -- but also requires that the power for the
>>latch's electronics has to be on.
> 
>I was under the impression that glycine was required for the NMDA channel
>to operate.  Is this in fact true?
Yes glycine is required as a cofactor to activate NMDA receptors. > 
> 
>>      Until the discovery of the NMDA channel, all channels had either
>>been operated by voltage alone (as in the sodium and potassium channels
>>for the impulse) or by neurotransmitter alone.
> 
>Just as an aside here, are voltage channels (in mammals at least) ever
>involved in conveyance of impulses from one neuron to another, or are
>they involved only in propagation of action potential (and dendritic
>potential?)
> 
>>neurophysiologists -- the calcium entry points to a mechanism for short-
>>term memory spanning many minutes.  In the hippocampus (an old part
>>of the cortex with a simpler layered structure), long-term potentiation
>>sometimes lasts for days, and part of the reason for LTP is the NMDA
>>business.
> 
>Is there any mechanism yet for memory lasting beyond several days, and
>more importantly for converting LTP into this type of memory?
> It was my understanding that LTP can last for weeks in some preps- if you
really want them I can give you some references.  I also think that both NMDA
and non-NMDA receptors are responsible for LTP. There are some reviews (recent)
in Ann.Rev.Neurosci. and also a series of articles on excitatory amino acids 
in Trends in Pharm. Sci. (TiPS) in the 1991 issues. 
>>    William H. Calvin   WCalvin at U.Washington.edu
> 
> 
>-- 
>|  Bill White   +1-614-594-3434     | bwhite at oucsace.cs.ohiou.edu             |
>|  31 Curran Dr., Athens OH  45701  | bwhite at bigbird.cs.ohiou.edu (alternate) |
>|  SCA: Erasmus Marwick, Dernehealde Pursuivant, Dernehealde, Middle Kingdom  |



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