On Thu, 27 Jan 2000, Rob Flint wrote:
> Can anyone give me an example of antidromic conduction in the CNS and what
> purpose it serves? I have a student that understands the basics, but I'm
> having a hard time conveying its purpose.
Ok, let me have a go (subject, as always, to correction by David
Epstein):
The traditional view is that antidromic conduction is an evolutionary
adaptation that exists merely to help neurophysiologists out. That is,
nature intended neuronal conduction to proceed from dendrite to axon
terminal only, and it's a happy accident that it can also go the other
way, at least until it encounters a synapse. So an example of
antidromic conduction would be a neurophysiologist sticking
a pair of microelectrodes into a nerve pathway. Stimulation from A to
B works; stimulation from B to A (the antidromic direction) doesn't.
She therefore infers that there must be a synapse in the pathway.
However, I understand that there is some evidence that when a neuron
fires (at the axon hillock, the point where the neuron body meets the
axon), it conducts (of course) forward along the axon, but also
backwards (antidromically) into the cell body and out to the
dendrites. This antidromic "invasion" may regulate the rate at which
the neuron can fire. I seem to recall that there may be special
retrograde neurotransmitters (such as nitric oxide, NO) which are
released in a backward direction across the synapse as a result of
such an effect.
Now I'll check Kandel (Essentials, 1995) to see if I'm right. No entry
for "antidromic", unfortunately, and only the briefest of mention of
NO. Hmmm.
Stephen
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
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