A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, in
fulfillment of the requirements for the degree of Doctor of Philosophy.
Johannesburg, 2015 / Cetaceans show an unusual form of mammalian sleep, with unihemispheric slow waves
(USWS), suppressed REM sleep and continuous bodily movement, however the mechanism by
which USWS occurs is unclear. This thesis describes the detailed anatomy of the neural systems
systems involved in the control and regulation of sleep in the basal forebrain, diencephalon,
midbrain and pons in three Cetartiodactyla species namely the Harbour porpoise, Northern
minke whale and the Hippopotamus, as well as a broader study of the orexinergic system in
Cetartiodactyls by means of immunohistochemistry and stereological analysis. All the neural
elements involved in sleep regulation and control found in bihemispheric sleeping mammals
were present in the harbour porpoise, minke whale and hippopotamus with no specific nuclei
being absent, and the only novel nuclei being identified was the parvocellular orexinergic cluster
in the hypothalamus- a feature seen in cetartiodactyla and the Africa elephant. This qualitative
similarity of nuclear organization relates to the cholinergic, noradrenergic, serotonergic and
orexinergic systems and is extended to the GABAergic elements involved with these nuclei.
Quantitative analysis of the cholinergic and noradrenergic nuclei of the pontine region and the
orexinergic nuclei of the hypothalamus revealed that in comparison to other mammals, the
numbers of pontine cholinergic, noradrenergic and orexinergic neurons are markedly higher in
the harbour porpoise and minke whale than in other large-brained bihemispheric sleeping
mammals previously examined. Furthermore, the diminutive telencephalic commissures (anterior
commissure, corpus callosum and hippocampal commissure) along with an enlarged posterior
commissure and supernumerary pontine cholinergic and noradrenergic neurons in cetaceans
indicate that the control of unihemispheric slow wave sleep is likely to be a function of
interpontine competition, facilitated through the posterior commissure, in response to unilateral
telencephalic input related to the drive for sleep. In addition, an expanded peripheral division of
the dorsal raphe nuclear complex appears likely to play a role in the suppression of REM sleep in
cetaceans. Thus, this thesis provides several clues to the understanding of the neural control of
the unusual sleep phenomenology present in cetaceans
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/18674 |
| Date | 16 September 2015 |
| Creators | Dell, Leigh-Anne |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
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