Coordinated dynamics of excitatory and inhibitory synapse assembly.

Neural circuits composed of multitudes of diverse synaptic connections self-organize during mammalian brain development. A balance between excitatory and inhibitory synaptic function is required for information processing by these neural circuits. Despite the importance of this balance, the interplay between excitatory and inhibitory synaptic assembly during circuit establishment remains unclear due to a lack of means to monitor both processes simultaneously. Here, we develop imaging approaches to visualize and track excitatory and inhibitory synapses concurrently. By applying these approaches, we find that despite continual dynamics, excitatory and inhibitory synaptic density remain at synchronized levels during synaptogenesis. These results support coordinated excitatory and inhibitory synapse assembly to maintain functional balance despite continual synaptic turnover.