2-Deoxyglucose-Induced Long-Term Potentiation Of Monosynaptic Ipsp's In Ca1 Hippocampal Neurons. Kreþimir Krnjeviþ and Yong-Tao Zhao. Anaesthesia Research Department, McGill University, Montr‚al, QC, H3G 1Y6 Canada.
APStracts 6:0513N, 1999.
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 IPSPs (under current-clamp) and 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 hr, and many little or none -- overall there was a significiant 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 ñ 10.25% (for n=24, P=0.0023) and 36.5 ñ 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, though smaller and more variable, 2-DG-induced LTP of inhibitory synapses appears to be broadly similar to the 2-DG-induced LTP of EPSPs previously observed in CA1.
Received 2 July 1999; accepted in final form 8 October 1999.
APS Manuscript Number J542-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999