Lateral entorhinal cortex neurons that project to nucleus accumbens mediate contextual associative memory

LEC-NAc neurons are activated by retrieval of context. (A) Circuit-tagging method to label LEC-NAc neurons with GFP. Cre-dependent Rosa26^eGFP-L10a male and female mice received intracranial infusion of a retrograde Cre virus (HSVrg-hEf1α-Cre) to drive expression of GFP in LEC-NAc neurons. (B) Experimental approach schematic and timeline of brain extraction for c-fos immunohistochemistry. (C) Representative 20 fluorescent images from LEC showing GFP + cells (left, magenta), c-fos + cells (middle, cyan), and merged image (right). White arrows indicate overlap and denote c-fos + GFP + LEC-NAc neurons. (D) Quantification of cell counts in each ROI (per mm²) expressing GFP (left), c-fos (middle), and colabeled (right) in Home (n = 6 mice), No CPP Test (n = 5 mice), Sal CPP Test (n = 5 mice), and Coc CPP Test groups (n = 5 mice). (E) Quantification of cell counts in each ROI (per mm²) expressing GFP (left), c-fos (middle), and colabeled (right) in Home (n = 6 mice; same control used in D), No CFC Test (n = 6 mice), Context Test (n = 5 mice), and CFC Test groups (n = 6 mice). One-way ANOVA followed by Holm–Sidak post hoc comparisons; (*) P < 0.05, (**) P < 0.01, (***) P < 0.001, (****) P < 0.0001.