Figure 6. Distribution of axon collaterals from mPFC-projecting and M1-projecting LC-NE neurons differs from that of the LC as a whole and from each other. Bar graphs show fractional distribution of labeled mPFC-projecting, M1-projecting, or all LC-NE neurons at select target regions. Axon density at each region is represented as a fraction of labeled axons in all imaged regions. Bar graph data are mean ± SEM and were analyzed by two-way repeated measures ANOVA. A, Comparison of mPFC-projecting (n = 4 mice, EGFP+) and all LC-NE neurons (n = 7 mice, sum of EGFP+ and tdTomato+ axons). LC subpopulation by target region interaction: F(17,153) = 8.072, p < 0.0001. Bonferroni post hoc test, ****p < 0.0001 [95% confidence interval of difference (CI of diff.): mPFC, −0.1441 to −0.06482; Cg Ctx, −0.1059 to −0.02655; AV, 0.03218 to 0.1115]. B, Comparison of M1-projecting (n = 3 mice, EGFP+) and all LC-NE neurons (as above). LC subpopulation by target region interaction: F(17,136) = 21.87, p < 0.0001. Bonferroni post hoc test, *p = 0.0176, Cg Ctx (95% CI of diff.: −0.08,684 to −0.004373), *p = 0.0117 PV (95% CI of diff.: 0.005982 to 0.08845), ****p < 0.0001 (95% CI of diff.: mPFC, −0.2037 to −0.1213; M1, −0.2007 to −0.1182; AV, 0.06125 to 0.1437). C, Comparison of mPFC-projecting and M1-projecting LC-NE neurons. Injection site by target region interaction: F(17,85) = 5.152, p < 0.0001. Bonferroni post hoc test, *p < 0.0217 (95% CI of diff.: 0.004639 to 0.1114), ****p < 0.0001 (95% CI of diff.: 0.08626 to 0.1930).