Fig. 5.

LC→mPFC neurons promote motor hyperactivity and exploration in the elevated plus maze. The experimental timeline is shown in A. Animals underwent a surgical procedure to inject CAV2-PRS-CreV5 bilaterally in mPFC and AAV-hSyn-DIO-hM3Dq-mCherry, AAV-hSyn-DIO-hM4Di-mCherry, or AAV-hSyn-DIO-mCherry bilaterally in LC. Three weeks later, all rats received an IP injection of 2.5 mg/kg CNO. Half an hour later, rats expressing hM3Dq underwent control conditions (n = 4), and rats expressing hM4Di underwent stressor exposure (n = 4). Rats expressing mCherry without a DREADD as a control were exposed to either control (n = 4) or stress (n = 4). Behavior was then assessed in the EPM and animals were returned to their home cages. One week later, behavior was assessed in the OFT. Rats were then perfused for verification of injection sites and transgene expression. Both percent open arm time and percent time freezing in the EPM were square root transformed to satisfy requirements for parametric statistical testing. (B) Rats whose LC→mPFC cells expressed hM3Dq and were activated prior to control conditions spent a significantly greater percentage of time in the open arms than control rats that expressed mCherry in LC→mPFC cells. Stressor-exposed rats expressing mCherry in LC→mPFC cells also spent significantly less time in time in the open arms than control rats expressing mCherry in LC→mPFC cells (shown as median with interquartile range). (C) Rats whose LC→mPFC cells expressed hM4Di and were inhibited prior to stressor exposure spent a significantly greater percentage of time freezing in the EPM than stressed rats that expressed mCherry in LC→mPFC projection cells. Stressor-exposed rats expressing mCherry in LC→mPFC cells also spent significantly more time freezing than control rats expressing mCherry in LC→mPFC cells (shown as median with interquartile range). Rats that had their LC→mPFC cells activated prior to control conditions spent also significantly greater percentage of time mobile in the EPM than control rats whose LC→mPFC cells were not activated prior to control conditions (D). Average speed in the EPM was square root transformed to satisfy requirements for parametric statistical testing and was not significantly affected by manipulation of the LC→mPFC pathway (E; shown as median with interquartile range). To determine if these effects simply reflected altered motor function rather than alterations in anxiety-like behavior, a distance index was calculated as the amount of distance traveled in the closed arms minus the distance traveled in the open arms divided by total distance traveled. A value of 1 would indicate all travel was in closed arms, while −1 would indicate all travel was in open arms. Activation of LC→mPFC cells prior to control conditions led to a significant decrease in distance index relative to rats whose LC→mPFC cells were not activated, indicating increased travel in the open arms relative to closed arms (F). Mean heat maps for activity in the EPM are shown in G. *: p < 0.05. †: p < 0.05 after square root transformation.