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Quantitative analysis of the cellular composition of rodent, primate and eulipotyphlan brains has shown that non-neuronal scaling rules are similar across these mammalian orders that diverged about 95 million years ago, and therefore appear to be conserved in evolution, while neuronal scaling rules appear to be free to vary in evolution in a clade-specific manner. Here we analyze the cellular scaling rules that apply to the brain of afrotherians, believed to be the first clade to radiate from the common eutherian ancestor. We find that afrotherians share non-neuronal scaling rules with rodents, primates and eulipotyphlans, as well as the coordinated scaling of numbers of neurons in the cerebral cortex and cerebellum. Afrotherians share with rodents and eulipotyphlans, but not with primates, the scaling of number of neurons in the cortex and in the cerebellum as a function of the number of neurons in the rest of the brain. Afrotheria also share with rodents and eulipotyphlans the neuronal scaling rules that apply to the cerebral cortex. Afrotherians share with rodents, but not with eulipotyphlans nor primates, the neuronal scaling rules that apply to the cerebellum. Importantly, the scaling of the folding index of the cerebral cortex with the number of neurons in the cerebral cortex is not shared by either afrotherians, rodents, or primates. The sharing of some neuronal scaling rules between afrotherians and rodents, and of some additional features with eulipotyphlans and primates, raise the interesting possibility that these shared characteristics applied to the common eutherian ancestor. In turn, the clade-specific characteristics that relate to the distribution of neurons along the surface of the cerebral cortex and to its degree of gyrification suggest that these characteristics compose an evolutionarily plastic suite of features that may have defined and distinguished mammalian groups in evolution. [ABSTRACT FROM AUTHOR]

Highlights: [•] The organization of calcium-binding protein systems is described in the brain of the giant Zambian mole-rat in relation to sleep-related neural systems. [•] These systems are organized in a similar manner to other rodents. [•] There are features that reflect both phylogenetic and functional signals in the evolution of these neural systems. [•] Two differences in the orexinergic terminal networks appear to correlate with different chronotypes within this species. [ABSTRACT FROM AUTHOR]

We investigated sleep in therock hyrax, Procavia capensis, a social mammal that typically lives in colonies on rocky outcrops throughout most parts of Southern Africa. The sleep of 5 wild-captured, adult rock hyraxes was recorded continuously for 72 h using telemetric relay of signals and allowing unimpeded movement. In addition to waking, slow wave sleep (SWS) and an unambiguous rapid eye movement (REM) state, a sleep state termed somnus innominatus (SI), characterized by low-voltage, high-frequency electroencephalogram, an electromyogram that stayed at the same amplitude as the preceding SWS episode and a mostly regular heart rate, were identified. If SI can be considered a form of low-voltage non-REM, the implication would be that the rock hyrax exhibits the lowest amount of REM recorded for any terrestrial mammal studied to date. Conversely, if SI is a form of REM sleep, it would lead to the classification of a novel subdivision of this state; however, further investigation would be required. The hyraxes spent on average 15.89 h (66.2%) of the time awake, 6.02 h (25.1%) in SWS, 43 min (3%) in SI and 6 min (0.4%) in REM. The unambiguous REM sleep amounts were on average less than 6 min/day. The most common state transition pathway in these animals was found to be wake → SWS → wake. No significant differences were noted with regard to total sleep time, number of episodes and episode duration for all states between the light and dark periods.Thus, prior classification of the rock hyrax as strongly diurnal does not appear to hold under controlled laboratory conditions. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: The organization of the nuclear subdivisions of the cholinergic, putative catecholaminergic and serotonergic systems of the brain of the elephant shrew (Elephantulus myurus) were determined following immunohistochemistry for choline acetyltransferase, tyrosine hydroxylase and serotonin, respectively. This was done in order to determine if differences in the nuclear organization of these systems in comparison to other mammals were evident and how any noted differences may relate to specialized behaviours of the elephant shrew. The elephant shrew belongs to the order Macroscelidea, and forms part of the Afrotherian mammalian cohort. In general, the organization of the nuclei of these systems resembled that described in other mammalian species. The cholinergic system showed many features in common with that seen in the rock hyrax, rodents and primates; however, specific differences include: (1) cholinergic neurons were observed in the superior and inferior colliculi, as well as the cochlear nuclei; (2) cholinergic neurons were not observed in the anterior nuclei of the dorsal thalamus as seen in the rock hyrax; and (3) cholinergic parvocellular nerve cells forming subdivisions of the laterodorsal and pedunculopontine tegmental nuclei were not observed at the midbrain/pons interface as seen in the rock hyrax. The organization of the putative catecholaminergic system was very similar to that seen in the rock hyrax and rodents except for the lack of the rodent specific C3 nucleus, the dorsal division of the anterior hypothalamic group (A15d) and the compact division of the locus coeruleus (A6c). The nuclear organization of the serotonergic system was identical to that seen in all eutherian mammals studied to date. The additional cholinergic neurons found in the cochlear nucleus and colliculi may relate to a specific acoustic signalling system observed in elephant shrews expressed when the animals are under stress or detect a predator. These neurons may then function to increase attention to this type of acoustic signal termed foot drumming. [Copyright &y& Elsevier]

Abstract: The nuclear subdivisions of the cholinergic, putative catecholaminergic and serotonergic systems within the brain of the rock hyrax (Procavia capensis) were identified following immunohistochemistry for acetylcholinesterase, tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the complement of nuclear subdivisions of these systems by comparing those of the rock hyrax to published studies of other mammals. The rock hyrax belongs to the order Hyracoidea and forms part of the Afroplacentalia mammalian cohort. For the most part, the nuclear organization of these three systems closely resembled that described for many other mammalian species. The nuclear organization of the serotonergic system was identical to that seen in all eutherian mammals. The nuclear organization of the putative catecholaminergic system was very similar to that seen in rodents except for the lack of a C3 nucleus and the compact division of the locus coeruleus (A6c). In addition, the diffuse locus coeruleus (A6d) appeared to contain very few tyrosine hydroxylase immunoreactive (TH+) neurons. The cholinergic system showed many features in common with that seen in both rodents and primates; however, there were three differences of note: (1) cholinergic neurons were observed in the anterior nuclei of the dorsal thalamus; (2) cholinergic parvocellular nerve cells, probably representing interneurons, forming subdivisions of the laterodorsal and pedunculopontine tegmental nuclei were observed at the midbrain/pons interface; and (3) a large number of cholinergic nerve cells in the periventricular grey of the medulla oblongata were observed. Thus, while there are many similarities to other mammalian species, the nuclear organization of these systems in the rock hyrax shows specific differences to what has been observed previously in other mammals. These differences are discussed in both a functional and phylogenetic perspective. [Copyright &y& Elsevier]

The Arabian oryx, Oryx leucoryx , is a member of the superorder Cetartiodactyla and is native to the Arabian Desert. The desert environment can be considered extreme in which to sleep, as the ranges of temperatures experienced are beyond what most mammals encounter. The current study describes the nuclear organization and neuronal morphology of the systems that have been implicated in sleep control in other mammals for the Arabian oryx. The nuclei delineated include those revealed immunohistochemically as belonging to the cholinergic, catecholaminergic, serotonergic and orexinergic systems within the basal forebrain, hypothalamus, midbrain and pons. In addition, we examined the GABAergic neurons and their terminal networks surrounding or within these nuclei. The majority of the neuronal systems examined followed the typical mammalian organizational plan, but some differences were observed: (1) the neuronal morphology of the cholinergic laterodorsal tegmental (LDT) and pedunculopontine tegmental (PPT) nuclei, as well as the parvocellular subdivision of the orexinergic main cluster, exhibited Cetartiodactyl-specific features; (2) the dorsal division of the catecholaminergic anterior hypothalamic group (A15d), which has not been reported in any member of the Artiodactyla studied to date, was present in the brain of the Arabian oryx; and (3) the catecholaminergic tuberal cell group (A12) was notably more expansive than previously seen in any other mammal. The A12 nucleus has been associated functionally to osmoregulation in other mammals, and thus its expansion could potentially be a species specific feature of the Arabian oryx given their native desert environment and the need for extreme water conservation. [ABSTRACT FROM AUTHOR]

Abstract: The current correspondence describes the in situ perfusion-fixation of the brain of the African elephant. Due to both the large size of proboscidean brains and the complex behaviour of these species, the acquisition of good quality material for comparative neuroanatomical analysis from these species is important. Three male African elephants (20–30 years) that were to be culled as part of a larger population management strategy were used. The animals were humanely euthanized and the head removed from the body. Large tubes were inserted into to the carotid arteries and the cranial vasculature flushed with a rapid (20min) rinse of 100l of cold saline (4°C). Following the rinse the head was perfusion-fixed with a slower rinse (40min) of 100l of cold (4°C) 4% paraformaldehyde in 0.1M phosphate buffer. This procedure resulted in well-fixed neural and other tissue. After perfusion the brains were removed from the skull with the aid of power tools, a procedure taking between 2 and 6h. The brains were immediately post-fixed in the same solution for 72h at 4°C. The brains were subsequently placed in a sucrose solution and finally an antifreeze solution and are stored in a −20°C freezer. The acquisition of high quality neural material from African elephants that can be used for immunohistochemistry and electron microscopy is of importance in understanding the “hardware” underlying the behaviour of this species. This technique can be used on a variety of large mammals to obtain high quality material for comparative neuroanatomical studies. [Copyright &y& Elsevier]