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