Optogenetic Analysis of the Function of neural Networks and synaptic Transmission in Caenorhabditis elegans

The transparent nematode Caenorhabditis elegans with its anatomically well-defined nervous system of 302 neurons that regulate quantifiable behaviors, is an ideal model system for the development and application of optogenetic methods. Optogenetically modified neurons can be acutely excited or inhibited by light, and the effects on a distinct behavior can be observed. Special lighting systems allow the manipulation of several nerve cells that act as "nodes" of small neural circuits, with different colors of light, so as to control different optogenetic tools. In addition, genetically encoded optical sensors for neuronal activity allow drawing conclusions even when the optogenetic intervention causes no obvious behavioral change. The stimulation of quantifiable behaviors allows analyzing the function of genes that are necessary in the corresponding neuron for encoding or amplification of the primary signal. Finally, following optogenetic stimulation, also the function of chemical synapses and their proteins can be analyzed by electrophysiology or electron microscopy.