bakedbeans at spam.not
Sat Feb 14 15:20:08 EST 2004
Thanks for your response. I had no idea what Mr. Collins was talking about.
I'd seen some of the papers you refer to in my searches. I believe the
lesion books I've seen say you can lesion with anodal or cathodal current
but the pole that produces hydrogen gas (I can't remember which) makes worse
lesions. They talk about using anything from 100 uA and up for large
lesions you can easily see with a low-power microscope. They suggest
changing the current to vary the size of the lesion. They also distinguish
between coagulation lesions (high current and long duration) from
electrolytic lesions (low current causing cell death).
Amazingly, the Weiss paper doesn't say what kind of electrode they used
(monopolar or bipolar or even composition). They also don't say what kind
of DC current they were giving...only the magnitude and duration. It's kind
of a funny paper. Their entire introduction is spent describing their
broken stimulator and attempts to fix it. They had been giving low
frequency (depotentiation) stimulation for 15 minutes to "quench" kindling,
but when they had their stimulator fixed they weren't able to quench
anymore. When they changed stimulators they still weren't able to
demonstrate their effect. When they had an engineer look at their
stimulators they discovered that they were pumping out low amplitude DC
current continuously, so they decided to see how this affects kindling.
They found that it mirrored their initial low frequency experiments.
They did silver staining for necrosis and GFAP staining for gliosis and
found that rats treated with DC showed increases in both these stains around
the electrode tip compared to controls. For some reason they still don't
think there was lesioning going on. They describe some acute in vitro
studies showing that cells survive (at least hours) after DC application.
Why not delayed cell death then? I suppose my question is that if you can
generate a great DC lesion with 100 uA for 10-20 seconds, then why not a
nifty lesion with 15 uA for 15 minutes? I think I remember the original
kindling studies by Goddard examining the effects of lesions on kindling and
found the same results Weiss is getting.
"Doktor DynaSoar" <targeting at OMCL.mil> wrote in message
news:e35s20dk5tpp96f6gve0ea1jhm9s3hmjo5 at 4ax.com...
> On Sat, 14 Feb 2004 01:53:28 -0500, "Klenow" <bakedbeans at spam.not>
> } The reason I'm asking about a lesion is that they claim there is a
> } long-lasting (maybe permanent) increase in seizure threshold akin to
> } kindling's permanent lowering of seizure threshold.
> You're wise to ask again. You've received a non-answer from our
> resident motor mouth.
> I can find no direct answer to your question in the literature. The
> closest I can find are references to use of DC current with respect to
> other damage. Depending upon polarity, it can help or hinder.
> Brain Res. 1992 May 1;579(1):32-42.
> The effect of direct current field polarity on recovery after acute
> experimental spinal cord injury. Fehlings MG, Tator CH.
> J Trauma. 1988 Nov;28(11):1548-52.
> Mammalian optic nerve regeneration following the application of
> electric fields. Politis MJ, Zanakis MF, Albala BJ.
> J Neurosci. 1983 Jan;3(1):153-60. Links
> Modification of retrograde degeneration in transected spinal axons of
> the lamprey by applied DC current. Roederer E, Goldberg NH, Cohen MJ.
> A change in seizure threshold could well be due to a change in
> response to GABAergic interneurons. A possibility is disruption of
> interneuronal gap junctions...
> Rev Neurosci. 2002;13(1):1-30.
> Axonal gap junctions between principal neurons: a novel source of
> network oscillations, and perhaps epileptogenesis. Traub RD, Draguhn
> A, Whittington MA, Baldeweg T, Bibbig A, Buhl EH, Schmitz D.
> ...resulting in decreased (amount or efficacy of) high frequency
> oscillations, which are mediated by the GABAergic interneurons, and
> can contribute to epileptiform activity...
> Epilepsia. 1996 Nov;37(11):1035-42.
> GABA-mediated synchronous potentials and seizure generation.
> Avoli M.
> On the other hand, you have in your possesion the paper that refers to
> it. At least one of the authors is listed as a contact, probably via
> email. They wouldn't do that if they didn't welcome good questions.
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