Postsynaptic expression of long-term potentiation in the rat dentate gyrus demonstrated by variance-mean analysis

Abstract

1. Long-term potentiation (LTP) of synaptic transmission is the putative mechanism underlying learning and memory. Despite intensive study, it remains controversial whether LTP is expressed at a pre- or postsynaptic locus. A new approach was used to investigate this question at excitatory synapses from the medical perforant path (MPP) onto granule cells in the hippocampal dentate gyrus. The variance of the evoked synaptic amplitude was plotted against mean synaptic amplitude at several different Cd2+ concentrations. The slope of the variance-mean plot estimates the average amplitude of the response following the release of a single vesicle of transmitter Q(av). A presynaptic modulation shoul..