Nuclear organization of catecholaminergic neurons in the brains of a lar gibbon and a chimpanzee

Abstract

Using tyrosine hydroxylase immunohistochemistry, we describe the nuclear parcellation of the catecholaminergic system in the brains of a lar gibbon (Hylobates lar) and a chimpanzee (Pan troglodytes). The parcellation of catecholaminergic nuclei in the brains of both apes is virtually identical to that observed in humans and shows very strong similarities to that observed in mammals more generally, particularly other primates. Specific variations of this system in the apes studied include an unusual high-density cluster of A10dc neurons, an enlarged retrorubral nucleus (A8), and an expanded distribution of the neurons forming the dorsolateral division of the locus coeruleus (A4). The additional A10dc neurons may improve dopaminergic modulation of

The Mammalian Locus Coeruleus Complex—Consistencies and Variances in Nuclear Organization

“…While generally quite a small number of neurons are found in the A4 and their distribution is limited, in both the lar gibbon and chimpanzee, A4 neurons were seen to extend considerably caudal in the ventral white matter of the cerebellum adjacent to the roof of the fourth ventricle [58]. Such an extension of A4 neurons is [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.…”

“…No specific variations have been noted in this nucleus across species and, as such, it is likely that this nucleus is homologous across mammals with its actions likely being analogous. [58]. Note that across mammalian species this columnar nucleus appears to be invariably present and is consistently located in the same region of the brain, that being ventrolateral to the subcoeruleus, diffuse portion (A7d), and dorsolateral to the superior olivary nuclear complex (SON).…”

“…However, in the species in which the A4 is present, the precise delineation of the boundary between the A4 and A6 neurons is not straightforward, as the A4 neurons appear to be a dorsocaudal continuation of the A6 neurons within the periventricular grey matter. While generally quite a small number of neurons are found in the A4 and their distribution is limited, in both the lar gibbon and chimpanzee, A4 neurons were seen to extend considerably caudal in the ventral white matter of the cerebellum adjacent to the roof of the fourth ventricle [58]. Such an extension of A4 neurons is [24], (c) the springhare (Pedetes capensis) [44], and (d) the lar gibbon (Hylobates lar) [58].…”

“…The definition of a reliable distinction between A4 and A6 would greatly assist in the interpretation of functional studies in laboratory rodents and primates. [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.…”

“…This indicates that these A7sc and A7d nuclei are likely to be homologous nuclei shared by all mammalian species studied to date. [50], (c) the ringtailed lemur (Lemur catta) [52], and (d) the chimpanzee (Pan troglodytes) [58]. Note the presence of the compact portion of the subcoeruleus (A7sc) in the dorsal aspect of the parvicellular reticular nucleus, with scattered more widely distributed neurons throughout the parvicellular reticular nucleus forming the diffuse portion of the subcoeruleus (A7d).…”