FIGURE 2.

The crescent-shaped locus coeruleus (LC) cradles the lateral surface of mouse Bar^CRH neurons. Panels (a–f) show the close relationship between LC (immunofluorescence labeling for tyrosine hydroxylase; TH, red) and Bar^CRH (GFP reporter for Crh, green). Bar^CRH neurons are found at middle-to-rostral levels of the LC (panels B–E, corresponding to the same approximate bregma levels as Figure 1, panels a–d). No neurons are double-labeled. Rostral to the LC, there are no more Bar^CRH neurons, though sparse, large neurons immunoreactive for TH extend rostrally into the periaqueductal gray. At caudal levels (panels e, f), there are few or no Bar^CRH neurons. At these caudal levels, LC dendrites project medially into a zone immediately behind the core of Bar. At central levels containing the core of Bar (panel d), its dorsolateral surface diverges from the dorsal LC; the resulting gap between Bar^CRH and the dorsal LC (dashed outline in panel d) is filled by a wedge of FoxP2/glutamatergic neurons, which are shown in Figure 6. Lines in panels (d–f) mark the ependymal surface of the fourth ventricle. Scale bar is 100 μm and applies to all panels