DC lesion?

k p Collins kpaulc at [----------]earthlink.net
Sat Feb 14 03:51:55 EST 2004


Thanks for posting this clarifing information.

The "low frequency stimulation" is =important=.

The DC =does= instantiate a "tuning-precision void" -
imposes disorder upon the kindling dynamics [and
'normal' dynamics as well, which should also be
observable through subtle measures with respect to
"supersystem configuration" [AoK, Ap5]].

K. P. Collins

"Klenow" <bakedbeans at spam.not> wrote in message
news:afkXb.32855$9U3.29342 at fe09.usenetserver.com...
> In our journal club, we were discussing their chapter in the book Kindling
5
> where they describe the Quenching effect on kindling.  We're pretty
> skeptical about it so we looked to see what else they had done on it.  I'm
> curious to know what people think of this.
>
> Here's the article...
>
> 1: Exp Neurol.  1998 Nov;154(1):185-92.
>
> Quenching revisited: low level direct current inhibits amygdala-kindled
> seizures.
>
> Weiss SR, Eidsath A, Li XL, Heynen T, Post RM.
>
> Biological Psychiatry Branch, National Institute of Mental Health,
Bethesda,
> Maryland 20892, USA.
>
> We have reported that low frequency stimulation (1 Hz for 15 min), applied
> after
> kindling stimulation of the amygdala, inhibited the development and
> expression
> of amygdala-kindled seizures, an effect we termed quenching. Subsequently,
> we
> discovered that this effect could only be achieved when certain
stimulators
> were
> used that also emitted a low-level direct current (DC). The studies
reported
> here indicate that DC, applied once daily for 15 min at intensities of
5-15
> microA, produced an intensity-related attenuation of kindling development
> and an
> increase in the afterdischarge threshold. This effect persisted in some
> animals
> for at least 1 month after discontinuation of the DC. In fully kindled
> animals,
> a robust increase in seizure threshold and persistent seizure inhibition
> were
> also observed using 10 microA of DC administered for 14 days. These
results
> clarify and extend our original findings of a quenching effect; however,
the
> mechanisms by which low level DC induces quenching require further
> elucidation.
>
>
> "NMF" <nm_fournier at ns.sympatico.ca> wrote in message
> news:JEjXb.17152$sO4.1541938 at news20.bellglobal.com...
> > Your right that really is a low current, however, depending on where
they
> > implanted the electrode you might be able produce an electrolytic lesion
> > with extremely low current.  It might depend on whether they were using
> > monophasic, biphasic fast ramps to deliever the stimulus current.
> However,
> > I think you said it was a low but constant current intensity, so square
> wave
> > currents (which can elicit lesions at very low current intensities) are
> out
> > of the picture.   For example, in the dentate with a low intensity
current
> > many cells have been shown to readily elicit prolonged burst firing.
The
> > prolonged period of burst firing will allow for greater calcium entrance
> > into the cell and the potential for deleterious accumulations of
> > intracellular calcium, activation of internal stores, and consequential
> > secondary messenger cascades.
> >
> > Generally the microcurrents used in many peripheral nerve stimulation
> > experiments are in the 50-100 microAmp range.  Moreover, they elicit
> potent
> > analgesic responses.  (This is the premise of electroacupuncture
> paradigms).
> > So definitely potent cellular responses are likely at the low currents
you
> > suggest.  As an aside point, even picotesla intensity magnetic fields
have
> > been shown to elicit profound neuronal responses. (no evidence of cystic
> > lesions though).  So definitely low intensity currents can elicit potent
> > biological effects.
> >
> > Technically, it doesn't surprise me all that much that you can get a
> > deleterious effect with such low intensity.  The cellular responses to
> > electrical stimulation is often a U-shaped curve. With extremely minimal
> > currents eliciting similar effects to that of high intensity currents.
In
> > this case its probably the temporal component (the fact that its a long
> > duration low intensity current) that is causing the effect similar to
what
> > would be encountered at higher intensity currents but have short time
> range.
> > That is also a common finding in sensory and motoric systems.  But its
> also
> > a routine finding in the literature involving learning and LTP vs. LTD
> > (long-term potentation vs. long-term depression), where the specific
level
> > of current intensity determines which type of behavioral (physiological)
> > response occurs.
> >
> > I wouldn't mind if you provided the citation to that paper.
> >
> > Thanks,
> >
> > NMF
> >
> >
> >
> > "Klenow" <bakedbeans at spam.not> wrote in message
> > news:PxiXb.9020$%h1.7659 at fe24.usenetserver.com...
> > >
> > > I've recently read a paper looking at the effects of 15 minutes of
> direct
> > > current stimulation (5-15 uA) through a chronic indwelling electrode
on
> > > kindled seizure thresholds in rats.  Can this type of stimulation
cause
> an
> > > electrolytic lesion at the electrode tip even with such low current?
> I've
> > > been looking through brain stimulation books and can't find an answer.
> > >
> > > --
> > > -----
> > >
> > >
> > >
> >
> >
>
>
>





More information about the Neur-sci mailing list