The use of optogenetic vector constructs as a dynamic neuronal tracer

Optogenetic vector constructs provide a novel technique that allows reversible light activation or deactivation of individual brain circuits. Although these techniques are promising, the transport activity of the individual vector constructs has never been documented. Because the analysis of optogenetic experiments could vary dramatically based on whether the vector constructs are transported anterogradely, retrogradely, or trans-synaptically; the transport activity for each vector construct must be documented. The results describe the transport of the AAV5-CaMKIIa-eNpHR 3.0-EYFP vector construct obtained from the stock stored at UNC Vector Core at Chapel Hill, NC. Injection into the amygdala showed both terminal and neuronal labeling in areas known to project to and receive projections from the amygdala, however no trans-synaptic labeling was observed. These results indicate that the vector is transported readily in both anterograde and retrograde directions. Because the full pathway seems to be labeled, it is possible that light may activate the light-sensitive chloride channels at any portion of the pathway. Therefore care must be taken when analyzing the results of light activation so that the results reflect all pathways that could be influenced by the light.