Optogenetics is a powerful tool for manipulating neuronal activity with high temporal and spatial precision. In the nematode C. elegans optogentics is especially useful and easy to apply. This is because C. elegans is translucent, so its neurons are highly accessible to optic stimulation. In addition, many of its neurons can be exclusively targeted using cell-specific promoters. We have recently taken advantage of optogentics to deliver artificial patterns of prolonged activation to a class of mechanosensory neurons, called touch receptor neurons (TRNs) in worms that lack touch sensation due to a genetic mutation. Our aim was to examine whether we can counteract the effects of sensory loss by artificially activating the sensory neurons. Here we describe in detail the various components of the protocol that we used. This consists of exposing worms expressing the light-sensitive ion channel Channelrohdopsin 2 (ChR2) in TRNs to long-term random flashes of light.
[Background] Artificial optogenetic stimulation (or silencing) of neurons has become of broad use in neuroscientific research. The powerful model organism, C. elegans, is particularly amenable to optogenetic manipulation (Nagel et al., 2005), and multiple groups have developed a range of techniques for delivering artificial brief patterns of stimulation with high temporal and spatial precision (Leifer et al., 2011; Stirman et al., 2011) and in combination with behavioral (Kocabas et al., 2012) and calcium imaging (Guo et al., 2009) or electrophysiological (Lindsay et al., 2011) readouts. We were interested in establishing a long-term stimulation protocol that would substitute natural ongoing activity in mechanosensory neurons deprived of sensory input (Rabinowitch et al., 2016). Our protocol integrates previous C. elegans optogenetic protocols, but focuses on chronic rather than transient stimulation.
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