Mapping Synaptic Inputs to Oligodendroglial Cells Using In Vivo Monosynaptic Viral Tracing

Oligodendroglial precursor cells (OPCs) are a non-neuronal cell type in the brain that receives synaptic inputs. Electrophysiological and ultrastructural evidence demonstrates excitatory and inhibitory synapses between neurons and OPCs. Previous mapping efforts reveal brain-wide afferent connectivity into OPCs from functionally interconnected brain regions, findings that demonstrate the remarkable extent of neuron-OPC synapses. While the function of neuron-to-OPC synapses remains somewhat enigmatic, these connections represent a clear mechanism of neuron-oligodendroglial interactions. Neuronal activity can regulate OPC proliferation, and generation of new oligodendrocytes and adaptive myelin changes are necessary for certain forms of learning and memory in the healthy brain. Understanding the neural networks from which oligodendroglial cells receive input from may reveal how OPCs process information in different contexts and the function of these connections. Here, we summarize a useful synaptic tracing method, monosynaptic retrograde rabies tracing, and how it can be adapted for mapping synaptic inputs to oligodendroglial cells.