How can GABA inhibit a neuron even when it barely changes the voltage? · Grey Matter

When the chloride equilibrium potential sits close to the resting voltage, opening GABA-A channels moves the voltage little, but the open channels still make the membrane leakier.

How can GABA inhibit a neuron even when it barely changes the voltage?

When the chloride equilibrium potential sits close to the resting voltage, opening GABA-A channels moves the voltage little, but the open channels still make the membrane leakier. Excitatory current arriving at the same moment then escapes through that leak instead of charging the membrane, so an input that would have reached threshold falls short. This is shunting inhibition: it divides the effect of excitation more than it subtracts from the voltage. It is strongest when the GABA synapses sit between the excitatory inputs and the spike initiation zone, on the soma or the axon initial segment.