• 1
    The mechanisms of long-term potentiation (LTP) and long-term depression (LTD) induced by brief high frequency stimulation (HFS), paired with a particular pattern and amplitude of depolarisation has been investigated in the medial perforant pathway of the dentate gyrus of the 2- to 3-week-old rat hippocampus in vitro.
  • 2
    N-Methyl-D-aspartate (NMDA) receptor (NMDAR) activation was measured quantitatively during HFS-induced NMDAR-dependent LTP, LTD and at the LTD-LTP crossover point in order to test the hypothesis that the induction of the particular form of plasticity depends on the intensity of NMDAR activation.
  • 3
    The induction of LTD, the LTD-LTP crossover point and LTP was associated with an increasing NMDAR charge transfer.
  • 4
    In addition to the NMDAR-dependent LTD, a group I metabotropic glutamate receptor (mGluR)-dependent LTD could be induced by high intensity HFS paired with depolarisation under conditions of NMDAR inhibition.
  • 5
    The induction of mGluR-dependent LTD requires membrane depolarisation, Ca2+ influx via L-type Ca2+ channels and a rise in intracellular Ca2+.
  • 6
    Quantal analysis involving minimal stimulation demonstrated that the mGluR-dependent LTD induction was associated with a decrease in potency and an increase in failure rate.