clohr at neurobio.arizona.edu (Christian Lohr) writes:
> Bill,
> your statement may be a bit misleading. The 'voltage dependence' of the
> NMDA receptor is different from that of the group of voltage-dependent
> (or voltage-activated) ion channels. The NMDA receptor is blocked from
> outside by magnesium ions at the resting potential. When the membrane
> depolarizes, magnesium is released and the channel can open when
> activated by glutamate. Thus, it is not a real voltage dependence. The
> channel can also be opened by glutamate at the resting membrane
> potential when magnesium is removed from the external solution.
> Calcium can enter the spines also through the receptor channel of the
> AMPA-type of glutamate receptors (Eilers & Konnerth, Nature 1995), and
> can be released from intracellular stores in the spines by activating
> metabotropic glutamate receptors (Finch & Augustine, Nature 1998;
> Takechi et al, Nature 1998). Check reviews for detailes:
> Yuste et al, Nature Neuroscience 3, 2000
> Berridge, Neuron 21, 1998
>> Cheers
> Chris
Well, asn you point out, I did simplify things a bit in the interest
of understandability, but my impression is that calling a channel
"voltage dependent" just means that the permeability is affected by
the membrane potential, and doesn't automatically say anything about
the mechanism that brings this about.
-- Bill
