Figure 1. Transfected mPFC→PAG neurons arise mainly from the pre-limbic (PrL) cortex.
(A) Intersectional viral vector strategy. We used a retrograde canine adenovirus and Cre-dependent adeno-associated viral vectors to express genetically encoded actuators (both channelrhodopsin-2 [ChR2] and hMD4i) within medial prefrontal cortex (mPFC) neurons that project to the periaqueductal grey (PAG). (B) Photomicrograph of mPFC showing labelled neurons residing mainly in the PrL cortex. (C) PrL cortex with colocalisation of mCherry (hM4Di) and EYFP (ChR2) in neurons projecting to PAG (many examples but several marked with white arrows). (D) Conjunction plot illustrating location of mPFC→PAG neurons throughout the mPFC (n=3 rats). Darker shading indicates positional overlap of positively labelled (hM4Di) neurons from more than one animal (light=1 animal, mid=2, and dark=3). Dotted red line demarks the PrL cortex. (E) Comparative distribution of mPFC→PAG neurons throughout the cortex (mean ± SEM). (F) Photomicrograph showing ChR2-EYFP and hM4Di-mCherry containing fibres from mPFC projecting to the ventrolateral region of PAG (many examples but several marked with white arrows).
Figure 1—figure supplement 1. There was negligible expression of channelrhodopsin-2 (ChR2)-EYP and hM4Di-mCherry in control animals that did not receive CAV–CMV–CRE into the periaqueductal grey.
