Probing the polarity of spontaneous perisomatic GABAergic synaptic transmission in the mouse CA3 circuit in vivo Graphical abstract Highlights d CA3 PV-interneurons generate perisomatic unitary GABAergic field potentials in vivo d GABAergic unitary fields can be used to probe inhibition with single-cell resolution d GABA reversal after acute seizures is restricted to the postictal silent period d GABAergic excitation during KA epileptogenesis is restricted to 0.6% of CA3 neurons