EFFECT OF THE MONO-SIALOGANGLIOSIDE AND TETRA-SIALOGANGLIOSIDE, GM1 AND GQ1B, ON LONG-TERM POTENTIATION IN THE CA1 HIPPOCAMPAL-NEURONS OF THE GUINEA-PIG

Effects of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on lon g-term potentiation (LTP) were investigated in the CA1 neurons of guin ea-pig hippocampal slices. The magnitude of LTP induced by a strong te tanus (100 Hz, 100 pulses) was not significantly affected by applicati on of either ganglioside. In contrast, when LTP was induced by a weak tetanus (100 Hz, 4 pulses), a significantly greater LTP was induced in the presence of either ganglioside. Similarly, when slices were incub ated in low-Ca2+ (1.0-1.1 mM) medium for more than 2 h, the LTP was us ually small or absent, but showed a significant increase in amplitude of population spike (A-PS) when the slices were incubated with either GM1 or GQ1b (4-5 mu g/ml). In addition, the application of GQ1b (4 mu g/ml) reversed the blocking effect of an NMDA-receptor antagonist, APP -5 (10 mu M), on the induction of LTP and resulted in forming LTP. Bas ed on these findings, we conclude that GM1 and GQ1b exert positive mod ulatory effects on the induction of LTP in hippocampal CA1 neurons and suggest that GM1 and GQ1b may participate in the induction of LTP as donors of Ca2+ ions.