Synaptic transmission between neurons plays a key role in signal transduction in the central nervous system (CNS). Postsynaptic currents can be routinely recorded using the patch-clamp technique but mechanisms underlying their kinetics are not entirely clear. Model simulations and experimental evidence indicate that the time course of synaptic agonist is extremely fast and short lasting implying that activation of postsynaptic receptors takes place in conditions of extreme non-equilibrium. For this reason, studies of postsynaptic receptors? kinetics requires ultrafast agonist application techniques able to mimic synaptic conditions, the goal that only recently has been technically achieved. In the present paper, examples of kinetic studies of synaptic currents and current responses to ultrafast agonist applications are presented. Examples are given that pharmacological modulation of synaptic receptors strongly depends on the non-equilibrium conditions of receptors? activation. Application of kinetic studies to determine subtypes of synaptic receptors are also presented and discussed.