Experiments by Huang lab show that early in cortical development, if GABA transmission is blocked in basket cell neurons, axons and preliminary synaptic connections with nearby pyramidal neurons are overabundant (row f = control; g and h show overgrowth). In col. 3, right, proto-synaptic structures called boutons (arrows) make contact with pyramidal cells; normally, GABA transmission triggers pruning of clusters seen in panels g3 and h3.

From article: "GABA signaling prunes back copious ‘provisional’ synapses during neural circuit assembly"