Synaptic inhibition plays an important role in sculpting signals within cortical microcircuits. At the most basic level, synaptic inhibition prevents hyperexcitability by providing activity-dependent inhibition. Inhibitory synaptic transmission uses a neurotransmitter called GABA. This interacts with GABA receptors, ion channels that are permeable to negatively charged chloride ions. Thus opening of these channels makes it harder for a neuron to generate an action potential.