Figure 2.

Low-magnification photomicrographs of the dorsolateral division of the locus coeruleus, or A4 nucleus, revealed with immunostaining for tyrosine hydroxylase, in (a) the four-toed sengi (Petrodromus tetradactylus) [16], (b) Wahlberg’s epauletted fruit bat (Epomophorus wahlbergi) [24], (c) the springhare (Pedetes capensis) [44], and (d) the lar gibbon (Hylobates lar) [58]. Note that across mammalian species this nucleus has a varied occurrence (Table 1), but when present is consistently located in the same location, that being dorsal to the locus coeruleus proper (A6) within the periventricular grey matter adjacent to the dorsomedial-most part of the superior cerebellar peduncle and cerebellar white matter. Insets in each image show a high-magnification image of the neurons that form the A4 nucleus in each species. In all images, dorsal is to the top and medial to the left. Scale bar in (b) = 250 µm and applies to (a,b). Scale bar in (d) = 500 µm and applies to (c,d). Scale bar in inset (c) = 25 µm and applies to all insets. 4V—fourth ventricle; Cb—cerebellum; GC—periventricular grey matter of the rostral hindbrain; scp—superior cerebellar peduncle.