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Conditioning?

Dr Richard M Vickery ucgbrmv at ucl.ac.uk
Wed Nov 3 10:32:29 EST 1993


bwhite at oucsace.cs.ohiou.edu (William E. White ) writes:

>I was under the impression that glycine was required for the NMDA channel
>to operate.  Is this in fact true?

	This is correct - glycine is a co-factor that has its own
	binding site on the NMDA receptor/channel, however, as someone
        else pointed out, the glycine concentration is probably normally
	sufficiently high that the response depends principally on the
	NMDA concentration, also there is residual function (~10% of 
	current) even in the absence of glycine.


>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?)

	Voltage-gated channels propogate the action potential 
	along the axon
	(which is an important part of conveying impulses from
	neurone to neurone  8-)  ) - they can not directly
	participate in synaptic transmission because this occurs
	across an electrically isolating cleft, where the signal
	is carried in a chemical form to ligand-gated channels
	(such as the various glutamate channels).  There are
	dendritic voltage-gated channels that may be important
	for conveying the synaptic input to the soma (where an
	action potential can be initiated), but more importantly
	for things like LTP, there are voltage-gated calcium channels
	which may provide a major part of the calcium increase needed
	in LTP or LTD - climbing fibre input to cerebellar Purkinje
	cells is a good example of this.

--
Richard M Vickery                  \ /     Our Quest is for meaning,
ucgbrmv at ucl.ac.uk                 (oVo)    but the Meaning IS the quest.
ph. 44-71-387 7050 x3256          )   (    
fax 44-71-383 7005                 ^ ^     Life's a Hoot!



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