Q about artificial and biological neural-nets

lamontg at u.washington.edu lamontg at u.washington.edu
Sun Feb 28 19:06:19 EST 1993


dfitts at carson.u.washington.edu (Douglas Fitts) writes:
>I don't know of any toxins that 
>specifically attack axons without attacking the entire cell.  Anybody want to
>jump in here?  I'd like to know if the complementary tool to excitotoxins 
>is available, especially if usable in vivo.

MDMA (3,4-methylenedioxymethamphetamine) along with MDA, MDE, and MBDB all
show neurotoxic effects that are limited to destroying axons while leaving
cell bodies (apparently) undamaged.  There then follows a period of
regrowth, although 5-HT and 5-HIAA levels (which are considered the
marker chemical) do not return completely to their pre-drug levels, but
do get close.

there are a whole slew of considerations to make when assessing the
neurotoxicity, excacerbated by the illegal status, recreational use
and emotional issues surrounding the drug, which is why i didn't specifically
mention it in the first message.  i can make a pretty damn good arguement
for the neurotoxicity being only applicable to animal models at larger doses
than encountered in typical human consumption, but its really not something
i want to argue over right now.

i'm more interested in the correctness of the "conventional wisdom" that
a drug which causes morphological changes in brain structure that damages
small individual units, must overall be damaging to the whole organism
or neural-net...

a *hypothetical* consideration that i've got is that this could be
functional, especially given the fact that its stimultaing changes in the
5-HT system.  the 5-HT system is one that pretty much stops modifying
its connections after adolescence (i've got a reference on this somewhere --
"the sleeping giant" and "seritonergic" are title keywords to check i
think...).  so, the "damage" may be more than offset by stimulating
axonal growth and possibly by wiping out some dysfunctional connections
which do not grow back...

i suppose i'll probably have to finish this up by mentioning that i'm not
trying to find evidence to support a "hey, it could make your brain work
better, everyone should take some!" stance towrds MDMA.  However, given
that there are reports of people gaining beneficial effects after taking
MDMA, it would seem logical to attempt to track down any possible
psychological or neurochemical explanations as to why -- because if
there is something to it, it would make a useful *clinical tool*.

(and MDMA has had an IND application approved by the FDA -- i believe its
being used in a clinical study now to aid terminally ill cancer patients.)
 
-- 
"Of all the strange 'crimes' that human beings have legislated out of 
nothing, 'blasphemy' is the most amazing--with 'obscenity' and 'indecent
exposure' fighting it out for second and third place."
                                    -- Lazarus Long



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