1. The effects of redox
reagents, 5,5'-dithiobis-2-nitrobenzoic
acid (
DTNB) and tris(carboxyethyl)
phosphine (
TCEP), on
anoxia-induced long-term potentiation (LTP) were investigated in CA1 hippocampal neurons using extracellular recording techniques. Experiments were performed in the presence of 0.1 mM
MgCl2 and 10 microM
6-cyano-7-nitroquinoxaline-2,3-dione (
CNQX) to pharmacologically isolate
N-methyl-D-aspartate (
NMDA) receptor-mediated responses. 2.
DTNB (200 microM), a
thiol oxidizing
reagent, reduces by 52 +/- 9% (mean +/- SE) (n = 9/9)
NMDA-receptor field potentials evoked by electrical stimulation of Schaffer collaterals and this effect could not be reversed by extensive washing. Nearly the same reduction of the initial response was obtained with different concentrations of
DTNB (100 and 500 microM), but the time required to reach the maximal inhibition was concentration-dependent. 3. In keeping with an earlier study
oxygen and
glucose deprivation for 2-3 min induced a long-term potentiation (LTP) of the
NMDA receptor response (+65 +/- 16%, n = 4/6). This potentiation was reversed by
DTNB (100-500 microM) (-47 +/- 18%; n = 4/4) and the initial LTP could not be restored upon extensive washing of the
drug. 4.
TCEP (200 microM), a
reagent which reduces S-S bond, amplified the electrically evoked
NMDA-receptor EPSP (+27 +/- 12%; n = 3). In addition,
TCEP (200 microM), nearly completely reversed the effect of
DTNB (200 microM) on
anoxia-induced LTP (+56 +/- 19%; n = 3/3). Preliminary results also indicate that
TCEP occlude anoxic-LTP (n = 3/4). 5. Following
DTNB (200 microM) treatment,
oxygen and
glucose deprivation did not generate anoxic LTP and extensive washing did not restore a potentiated
NMDA field potential. 6. These observations strongly suggest that the redox site of the
NMDA receptor is involved in the induction and the maintenance of the anoxic LTP of the
NMDA receptor-mediated response in CA1.