spreading of action potentials

Thomas Chimento chimento at ursa.arc.nasa.gov
Fri Oct 21 14:12:40 EST 1994


In article <388qc4$qeu at lace.Colorado.EDU>, dbeeman at dogstar.Colorado.edu (Dave Beeman) writes:
|> In article <Cxnpuz.5uv at brunel.ac.uk>, hssrkng at brunel.ac.uk (Kevin N Gurney) writes:
|> |> I am *not* a neuroscientist so I apologise if my questions appears
|> |> naieve.
|> |> 
|> |> I have recently started to investigate the dynamics of action-potential
|> |> production and have used the 'Neurokit' script-set in the Genesis
|> |> simulator to help my understanding. The most significant thing I
|> |> noticed was that the action potential, as well as propagating along the
|> |> axon, also propagates over the soma and dendritic tree. In the latter
|> |> case I presume this is done electrotonically. There appears to be no
|> |> mention of this kind of propagation in the usual text - One gets the
|> |> idea that action potential spikes propagate along axons alone.
|> |> 
|> |> My first question is: 
|> |> Is this behaviour an artifact of the simulator or is it `real'?
|> 
|> To gain some further understanding of the role of action potential
|> propagation in dendrites, you might try the "traub91" tutorial simulation
|> which comes with the GENESIS simulator.  It explores the behavior of the
|> Traub et al. CA3 pyramidal cell model (Journal of Neurophysiology, Vol. 66,
|> p.  635 (1991)).  The bursting behavior depends on the propagation of action
|> potentials from the soma to the dendrites, where voltage-activated calcium
|> channels are activated.
|> 
|> Dave Beeman

I co-authored a paper that was recently published in J. Neurophysiology 
(17)5 1994, 1883-1896, that discussed this phenomenon. We studied the
primary afferent fibers in the vestibular system - Our cells are rather
unusual morphologically, they have calyceal ending instead of the more 
traditional dendrites. The spike initiation zone is very close to the
synaptic input sites. There are also collateral processes that are
'efferent' to adjacent cells. These processes would be depolarized
sufficiently to release neurotransmitter as a result of the action
potential spreading distally. 
Thomas

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