Figure 1.

Optogenetic tools can be used in vivo while assessing rodent affective-like behaviors. (A) Depicted is a cartoon illustrating the current optogenetic expression systems used in vivo in rodent brains. Here we include the many versions of blue light (473 nm) activated channelrhodopins, the cation channels which depolarize neurons when exposed to blue light. Yellow light (561 nm) is used to activate haloprhodopsins, the chloride pumps which inhibit neurons. The OptoXRs, chimeras in which rhodopsin (shown in green) is fused to the intracellular portion of a GPCR (i.e., a Gs-coupled GPCR, shown in black); activation by light activates intracellular signaling cascades, eventually leading to transcriptional regulation in the nucleus (e.g., via increasing the phosphorylation of the transcription factor CREB). Finally, the LOV domain can sterically inhibit a specific protein (e.g., Rac1) to which it is fused; with exposure to blue light, an allosteric confirmation releases LOV from Rac1 and Rac1 signaling occurs eventually resulting in alterations in actin dymamics. (B) Depicted here is an example of the use of optogenetics with a common behavioral assay, social interaction, to evaluate depression-like behavior after chronic social defeat stress. Mice are tested for time spent in the interaction zone (near the novel mouse) or time spent in the corner zone (away from the novel mouse). Panels on the right show examples of a mouse avoiding the novel mouse (top right) or interacting with the novel mouse (bottom right) when neuronal activity is controlled in vivo with light optics (83).