anoxia

F. Frank LeFever flefever at ix.netcom.com
Sun Oct 18 20:06:19 EST 1998


This is very helpful!  I could have found such articles by Medline
search, but it would not have occured to me to look!  Your two sets of
articles make me think my suspicion was correct re the (narrow?) window
of opportunity for inducing rather than blocking LTP.

I will read these articles, of course, but I am wondering in advance:
will they address issues of degree of anoxia (e.g. effect of "hypoxia")
and/or duration? Perhaps research using "primed burst" LTP, which is
said to be more like natural processes than tetanic LTP is too recent
to be included, but I am wondering how it responds to the parameters
found significant for tetanic LTP; in some other studies, it has proven
vulnerable to some conditions to which tetanic LTP is resistant, i.e.
insensitive.

F. LeFever


In <362A070C.F62D8941 at venus.iteb.serpukhov.su> Alexey Semyanov
<semyanov at venus.iteb.serpukhov.su> writes: 
>
>Yes, there are two different types of facts about the role of an
anoxia in
>LTP.
>
>1 Anoxia can induce LTP:
>Hammond C, et al. Anoxic LTP sheds light on the multiple facets of
NMDA
>receptors. Trends Neurosci. 1994 17(11):497-503.
>Crepel V, et al. A selective LTP of NMDA receptor-mediated currents
induced
>by anoxia in CA1 hippocampal neurons. J Neurophysiol. 1993
70(5):2045-55.
>Crepel V, et al. Anoxia-induced LTP of isolated NMDA receptor-mediated
>synaptic responses. J Neurophysiol. 1993 69(5):1774-8.
>Hsu KS, et al. Characterization of the anoxia-induced long-term
synaptic
>potentiation in area CA1 of the rat hippocampus. Br J Pharmacol. 1997
>122(4):671-81.
>Huang CC, et al. Nitric oxide signalling is required for the
generation of
>anoxia-induced long-term potentiation in the hippocampus. Eur J
Neurosci.
>1997 9(10):2202-6.
>Gozlan H, et al. Anoxic LTP is mediated by the redox modulatory site
of the
>NMDA receptor. J Neurophysiol. 1994 72(6):3017-22.
>
>2 Anoxia inhibit tetanic LTP:
>Arai A, et al. Anoxia reveals a vulnerable period in the development
of
>long-term potentiation. Brain Res. 1990 19;511(2):353-7.
>Izumi Y, et al. Oxygen deprivation produces delayed inhibition of
long-term
>potentiation by activation of NMDA receptors and nitric oxide
synthase. J
>Cereb Blood Flow Metab. 1998 Jan;18(1):97-108.
>
>However, I think that these are not conflicting data. There are many
types
>of LTP. Tetanic LTP seems to have mainly presynaptic origin, but
anoxic may
>be NMDA receptor associated.
>
>------------------------------------------------------
>A. Semyanov, Ph.D.
> ITEB RAS, Pushchino,
>Moscow region, 142292, Russia
>------------------------------------------------------
>
>
>"F. Frank LeFever" wrote:
>
>> Sorry that I don't have info you need.  However, I need YOUR info:
can
>> you tell me more about anoxia inducing LTP?  Do you have references
to
>> published reports?  Just a guess: anoxia and many other brain
insults
>> can initiate intense excitotoxic (excitatory amino acid) reactions;
at
>> a given moment, NMDA activation and NO amplification might be just
at
>> the level to induce LTP. (outside this window of opportunity, I
think
>> it would block LTP--see Izumi & Zorumski)
>>
>> (If publication is in Russian,, OK; I can read NYEMNOGA...and I have
>> Russian friends.)
>>
>> F. Frank LeFever, Ph.D.
>> New York Neuropsychology Group
>>
>> In <36274082.8C9B9C74 at venus.iteb.serpukhov.su> Alexey Semyanov
>> <semyanov at venus.iteb.serpukhov.su> writes:
>> >
>> >Short-term potassium increase is known to lead long-lasting
increase
>> in
>> >synaptic efficiency. According to our own data it can lead
EPSP-spike
>> >potentiation in CA1 hippocampal slices. On other hand there are
some
>> >experimental evidences that brief anoxic episode can induce LTP
also.
>> >It seems to be due to potassium increase during anoxia.
>> >Unfortunately, when I attempt to test it changing solution with gas
>> >mixture O2+CO2 to solution with N2+CO2 I was not successful. I
haven’t
>> >seen any depression of responses during 30 min !!!
>> >The volume of my recording chamber is about 2 ml; it is open for
air.
>> >The speed of superfusion is 2.5 ml/min. I think this problem is
>> because
>> >of wrong chamber construction. Could anybody suggest me something
>> about
>> >this situation? I will be very grateful for suitable references or
>> >design of such chamber with a description.
>> >
>> >
>




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