Glutamate induces long-term increase in the frequency of single N-methyl-D-aspartate channel openings in hippocampal CA1 neurons examined in situ.

Long-term potentiation is currently a leading candidate for a physiological memory mechanism in CNS. The interpretation of this phenomenon is contradictory in many respects. However, there is clear evidence that long-term potentiation is critically dependent on activation of N-methyl-D-aspartate receptors. Recently it has been shown that extracellularly applied glutamate also induces long-lasting changes in the properties of synaptic transmission in the hippocampus that can be attributed to long-term potentiation. The involvement of presynaptic mechanisms has been reported. Here we demonstrate a definite increase in both the open time and open-state probability of N-methyl-D-aspartate-operated channels, induced by prolonged application of glutamate to hippocampal slices.