Mapping Synaptic Connectivity in the Cerebellar Cortex Using RuBi-Glutamate Uncaging

Synaptic functional organization of excitatory and inhibitory inputs in neuronal microcircuits organizes dynamics and underlies learning processes. Describing connectivity maps is, therefore, essential to bridge the gap between cellular neuroscience and behavior. Although in vivo extracellular recordings techniques can inform about neuronal discharge activity, patch-clamp recordings in brain slices enable synaptic mapping in principal neurons. Here, we describe a method allowing fast and reliable activation of presynaptic neurons on a wide area around the targeted cell and the establishment of excitatory synaptic connectivity maps. Specifically, we used glutamate uncaging (RuBi-glutamate) in combination with patterned light illumination to activate presynaptic neurons on acute cerebellar slices. Our goal is to describe a simple method to record, analyze, and reconstruct the functional synaptic organization of neuronal microcircuits in the cerebellum. This method may be applied in many other brain regions.