Dr Richard M Vickery (ucgbrmv at ucl.ac.uk) wrote:
>bwhite at oucsace.cs.ohiou.edu (William E. White ) writes:
> >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).
Apropos to channels which are both voltage- and transmitter-sensitive:
There is also some evidence of voltage-gated channels which shunt
certain cells -- this appears to *prevent* the neurons from reaching
the action potential threshold. In particular, I'm thinking of the
muscarine-sensitive potassium current (A-current) found in striatal
medium spiny cells:
Akins PT, Surmeier DJ, Kitai ST (1990) Muscarinic modulation of a
transient K+ conductance in rat neostriatal neurons, Nature
344:240-242.
This is part of the reason why striatal primary neurons are so quiet.
In this case, it looks as if voltage-gated channels are responsible
for preventing (rather than facilitating) synaptic transmission.
- - - - - - - - -
Chris Connolly, connolly at cs.umass.edu
Laboratory for Perceptual Robotics, UMass Amherst
