gamma-DGG (γ-DGG) is the most effective antagonist of the excitatory postsynaptic potentials (e.p.s.p.s). Its action is reversible and not associated with any change in the passive membrane properties of the granule cells or in the apparent reversal potential of the e.p.s.p.gamma-DGG blocks less at higher glutamate concentration. gamma-DGG (200-400 μM) in the bath decreases the miniature EPSC (mEPSC) amplitude by 26±2% (n=5 synapses) and shifts both the mEPSC amplitude distribution and the cumulative probability curve to the left [1]. The quantal analysis displays that the reduction in the e.p.s.p. paralleled the reduction in quantal size rather than quantal content, confirming a post-synaptic site of the action of gamma-DGG [2].