Figure 10.

A model on the role of presynaptic GABA_BR in regulating the development of inhibitory synapses. A developing GABAergic axon (light blue) explores potential synaptic targets (beige rectangles) by making transient synaptic contacts. Beige rectangles represent appropriate targets; rectangles with lines represent inappropriate targets. These transient contacts contain release machinery, such as synaptic vesicles (green filled circles) that are mobile (arrows) along the axon and mediate GABA release (boxed inset). Autocrine GABA signaling through presynaptic GABA_BR promotes actin polymerization likely through G protein signaling and stabilizes mobile synaptic vesicles at the developing terminal. Through synaptic activity and GABA_BR dependent recruitment and redistribution of presynaptic resource (e.g., synaptic vesicles), contacts at the inappropriate targets are eliminated whereas those at the appropriate targets are validated and strengthened (WT). In the absence of GABA_BR (GABA_BR^−/−), nascent contacts fail to stabilize mobile synaptic vesicle pools according to GABA release, leading to reduced bouton density and aberrant distribution along axon branch.