Anatomy of the orexinergic, serotonergic, cholinergic and catecholaminergic systems in the brains of apes
Date
2020
Authors
Williams, Victoria Mary Elizabeth
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Abstract
Using immunohistochemistry, the nuclear parcellation of the cholinergic,
catecholaminergic, serotonergic and orexinergic systems were described in two species of
apes, the lar gibbon and common chimpanzee. The data obtained from this dissertation shows
that these neuromodulatory systems are similar to that observed in a range of Eutherian
mammals, including other primates, especially humans. Despite the similarities, unique
features, in terms of neuronal morphology and distribution, were found within these
neuromodulatory systems that might be Hominoid- or primate-specific, including: 1) a novel
cluster of orexinergic neurons in the tuberal region of the hypothalamus, which to a certain
extent, is also present in the human hypothalamus, revealing that it is most likely a shared
feature of the Hominoidea; 2) an expansion of the lateral division of the serotonergic dorsal
raphe nuclear complex was only observed in the common chimpanzee, and it is also present
in humans; 3) the expansion of the cholinergic medullary tegmental field and cervical spinal
cord, which are only present in the apes, including humans; 4) the soma forming the
laterodorsal tegmental nucleus (LDT) were larger than the pedunculopontine (PPT) nucleus, which might be related to the size of the adult derivatives of the alar and basal plate; 5) the
distribution of the catecholaminergic neurons forming the retrorubral nucleus (A8) was
expanded in both apes, especially in the common chimpanzee, which is also present in
humans, but not in other primate species; and 6) the presence of a compact division of the
locus coeruleus (A6c), which has been found in other primates, but it is not present in other
mammals, except for megachiropteran bats, and thus might be an important indicator of phylogenetic relationships. Given the consistency across mammals, including primates, it is
advantageous to use animal models for the study of specific dysfunctions in these
neuromodulatory systems in humans at a systems level
Description
A thesis submitted to the School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand in fulfilment of the requirements for the degree of Doctor of
Philosophy