Although GABA is best known for its hyperpolarizing action and its role in synaptic inhibition, a depolarizing action was recognized in some of the very early studies of spinal cord and developing neural tissue.

Does GABA depolarize?

Two independent lines of optical and electrophysiological evidence suggest that GABA acts as a depolarizing neurotransmitter in the developing (P3–4) mouse occipital neocortex. (1) In cell-attached current-clamp recordings, GABA was found to induce depolarization in most neurons examined.

Which neurotransmitter causes hyperpolarization?

For example, when the neurotransmitter GABA (gamma-aminobutyric acid) is released from a presynaptic neuron, it binds to and opens Cl^– channels. Cl^– ions enter the cell and hyperpolarizes the membrane, making the neuron less likely to fire an action potential.