A comparison of viral strategies and model systems to target norepinephrine neurons in the locus coeruleus reveals high variability in transgene expression patterns
Fig 4
(A) Bilateral transduction efficacy (n = 5 animals in each group) using a single micropipette to sequentially infect both LC (2 × 300 nl). (B) Same as A, except that one micropipette was used for each LC (n = 2 animals in each group). (C) Fraction of animals with bilateral (solid) or unilateral (shaded) LC transduction upon LC injections with a single pipette vs. two pipettes. (D) Assessement of viral spread by injections of a ‘cre-switch’ construct leading to eGFP expression in a cre-dependent manner and tdTomato expression in cre-negative cells [45]. (E) Transgene expression in Dbhcre, Netcre and Thcre animals (n = 3 animals each) shows conditional eGFP expression in cre-positive cells (green) and tdTomato expression in cre-negative cells (magenta). LC-NE cells are visualized by immunostaining against TH (dark blue). Importantly, in animals without eGFP expression, cre-negative cells around the LC also lacked the expression of tdTomato, likely resulting from loss of the virus suspension to the ventricle. (F) Change of mediolateral coordinates for virus injections from ±0.9 mm to ±1.1 mm. (G) Bilateral transduction efficacy after using the new coordinates in transgenic or wild-type animals. (H) Fraction of conditionally eGFP-expressing animals with bilateral (solid) or unilateral (shaded) LC transduction upon LC injections at mediolateral coordinates of from ± 0.9 mm and ± 1.1 mm (e.g., pooled data from panel A/B vs. panel G, uppermost row). (I) Fraction of unconditionally fluorophore-expressing animals with bilateral (solid) or unilateral (shaded) LC transduction upon LC injections at mediolateral coordinates of ±0.9 mm and ±1.1 mm (e.g., pooled data from panel D vs. panel G, rows 2–5). ns = not significant, * for p < 0.05, chi-squared test.