The Journal of Neurophysiology Vol. 83 No. 2 February 2000, pp. 879-887
Copyright ©2000 by the American Physiological Society
2-Deoxyglucose-Induced Long-Term Potentiation of
Monosynaptic IPSPs in CA1 Hippocampal Neurons
Kre
imir
Krnjevi
and
Yong-Tao
Zhao
Anaesthesia Research Department, McGill University, Montreal,
Quebec H3G 1Y6, Canada
Krnjevi, Kreimir and
Yong-Tao Zhao.
2-Deoxyglucose-Induced Long-Term Potentiation of
Monosynaptic IPSPs in CA1 Hippocampal Neurons. J. Neurophysiol. 83: 879-887, 2000. In previous experiments on excitatory
synaptic transmission in CA1, temporary (10-20 min) replacement of
glucose with 10 mM 2-deoxyglucose (2-DG) consistently caused a marked
and very sustained potentiation (2-DG LTP). To find out whether 2-DG
has a similar effect on inhibitory synapses, we recorded
pharmacologically isolated mononosynaptic inhibitory postsynaptic
potentials (IPSPs; under current clamp) and inhibitory postsynaptic
currents (IPSCs; under voltage clamp); 2-DG was applied both in the
presence and the absence of antagonists of
N-methyl-D-aspartate (NMDA). In spite of
sharply varied results (some neurons showing large potentiation, lasting for >1 h, and many little or none), overall there was a
significant and similar potentiation of IPSP conductance, both for the
early (at 
30 ms) and later (at 140 ms) components of IPSPs or
IPSCs: by 35.1 ± 10.25% (mean ± SE; for
n = 24, P = 0.0023) and
36.5 ± 16.3% (for n = 19, P = 0.038), respectively. The similar potentiation
of the early and late IPSP points to a presynaptic mechanism of LTP.
Overall, the LTP was statistically significant only when 2-DG was
applied in the absence of glutamate antagonists. Tetanic stimulations
(in presence or absence of glutamate antagonists) only depressed IPSPs
(by half). In conclusion, although smaller and more variable,
2-DG-induced LTP of inhibitory synapses appears to be broadly similar
to the 2-DG-induced LTP of excitatory postsynaptic potentials
previously observed in CA1.
