Nuclear organization of cholinergic, putative catecholaminergic, serotonergic and orexinergic systems in the brain of the African pygmy mouse (Mus minutoides) : organizational complexity is preserved in small brains

This study investigated the nuclear organization of four immunohistochemically identifiable neural systems (cholinergic, catecholaminergic, serotonergic and orexinergic) within the brain of the African pygmy mouse (Mus minutoides). The African pygmy mice studied had a brain mass of around 275 mg, making these the smallest rodent brains to date in which these neural systems have been investigated. In contrast to the assumption that in this small brain there would be fewer subdivisions of these neural systems, we found that all nuclei generally observed for these systems in other rodent brains were also present in the brain of the African pygmy mouse. As with other rodents previously studied in the subfamily Murinae, we observed the presence of cortical cholinergic neurons and a compactly organized locus coeruleus. These two features of these systems have not been observed in the non-Murinae rodents studied to date. Thus, the African pygmy mouse displays what might be considered a typical Murinae brain organization, and despite its small size, the brain does not appear to be any less complexly organized than other rodent brains, even those that are over 100 times larger such as the Cape porcupine brain. The results are consistent with the notion that changes in brain size do not affect the evolution of nuclear organization of complex neural systems. Thus, species belonging to the same order generally have the same number and complement of the subdivisions, or nuclei, of specific neural systems despite differences in brain size, phenotype or time since evolutionary divergence.The South African National Research Foundation (PRM, NCB), SIDA (KF) and by a fellowship within the Postdoc-Programme of the German Academic Exchange Service, DAAD (NP).http://www.elsevier.com /locate/jchemneuab201

Nuclear organisation of some immunohistochemically identifiable neural systems in three Afrotherian species-Potomogale velox, Amblysomus hottentotus and Petrodromus tetradactylus

The present study describes the organization of the cholinergic, catecholaminergic, serotonergic and orexinergic (hypocretinergic) neurons in the brains of the giant otter shrew, the Hottentot golden mole and the four-toed sengi, three members of the mammalian super order Afrotheria. The aim of the present study was to investigate the possible differences in the nuclear complement of these neural systems in comparison to previous studies on other Afrotheria species and other mammalian species. Brains of the golden mole, sengi and giant otter shrew were coronally sectioned and immunohistochemically stained with antibodies against cholineacetyl-transferase, tyrosine hydroxylase, serotonin and orexin-A. The majority of nuclei revealed in the current study were similar between the species investigated, to other Afrotherian species investigated, and to other mammals, but certain differences in the nuclear complement highlighted phylogenetic interrelationships. The golden mole was seen to have cholinergic interneurons in the cerebral cortex, hippocampus, olfactory bulb and amygdala. The four-toed sengi had cholinergic neurons in both colliculi and in the cochlear nucleus, but lacked the catecholaminergic A15d group in the hypothalamus. In both the golden mole and the four-toed sengi, the locus coeruleus (A6d group) was made up of few neurons. The golden mole also exhibited an unusual foreshortening of the brain, such that a major kink in the brainstem was evident. The results of this study, framed in a phylogenetic context, appear to indicate that the golden mole and four-toed sengi share a more recent common ancestor that diverged from the tenrec lineage early in the phylogenetic history of the Afrotherians.The South African National Research Foundation (PRM and NCB), the Belgian co-operation service at the Royal Museum for Central Africa (EG), and by a fellowship within the Postdoctoral-Program of the German Academic Exchange Service, DAAD (NP).http://www.elsevier.com/locate/jchemneuhb2016Mammal Research InstituteZoology and Entomolog

The distribution of doublecortin-immunopositive cells in the brains of four afrotherian mammals : the Hottentot golden mole (Amblysomus hottentotus), the rock hyrax (Procavia capensis), the eastern rock sengi (Elephantulus myurus) and the four-toed sengi (Petrodromus tetradactylus)

Adult neurogenesis in the mammalian brain is now a widely accepted phenomenon, typically occurring in two forebrain structures: the subgranular zone (SGZ) of the hippocampal dentate gyrus and the subventricular zone (SVZ). Until recently, the majority of studies have focused on laboratory rodents, and it is under debate whether the process of adult neurogenesis occurs outside of the SGZ and the SVZ in other mammalian species. In the present study, we investigated potential adult neurogenetic sites in the brains of two elephant shrews/sengis, a golden mole and a rock hyrax, all members of the superorder Afrotheria. Doublecortin (DCX) immunoreactivity was used as a proxy to visualise adult neurogenesis, which is expressed in neuronal precursor cells and immature neurons. In all four species, densely packed DCX-positive cells were present in the SVZ, from where cells appear to migrate along the rostral migratory stream towards the olfactory bulb (OB). DCX-immunopositive cells were present in the granular cell layer and the glomerular layer of the OB. In the hippocampus, DCX-immunopositive cells were observed in the SGZ and in the granular layer of the dentate gyrus, with DCX-immunopositive processes extending into the molecular layer. In addition to these well-established adult neurogenic regions, DCX-immunopositive cells were also observed in layer II of the neocortex and the piriform cortex. While the present study reveals a similar pattern of adult neurogenesis to that reported previously in other mammals, further studies are needed to clarify if the cortical DCX-immunopositive cells are newly generated neurons or cells undergoing cortical remodelling.South African National Research Foundation, the Swiss-South African Joint Research Program, the Belgian co-operation service at the Royal Museum for Central Africa and by a fellowship within the Postdoctoral-Program of the German Academic Exchange Service, DAAD.http://www.karger.com/Journal/Home/223831hb201

Nuclear organisation of some immunohistochemically identifiable neural systems in five species of insectivore-Crocidura cyanea, Crocidura olivieri, Sylvisorex ollula, Paraechinus aethiopicus and Atelerix frontalis

The organization of the cholinergic, catecholaminergic, and serotonergic neurons in the brains of five species of insectivores and the orexinergic (hypocretinergic) system in four insectivore species is presented. We aimed to investigate the nuclear complement of these neural systems in comparison to those of other mammalian species. Brains of insectivores were coronally sectioned and immunohistochemically stained with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. The majority of nuclei were similar among the species investigated and to mammals in general, but certain differences in the nuclear complement highlighted potential phylogenetic interrelationships. In the cholinergic system, the three shrew species lacked parabigeminal and Edinger-Westphal nuclei. In addition, the appearance of the laterodorsal tegmental nucleus in all insectivores revealed a mediodorsal arch. All three of these features are the same as those present in microchiropterans. The catecholaminergic system of the three shrew species lacked the A4 and A15d nuclei, as well as having an incipient A9v nucleus, again features found in microchiropteran brains. The serotonergic and orexinergic systems of the insectivores are similar to those seen across most eutherian mammals. The analysis of similarities and differences across mammalian species indicates a potential phylogenetic relationship between the Soricidae (shrews) and the microchiropterans.This work was mainly supported by funding from the South African National Research Foundation (P.R.M.), by a fellowship within the Postdoctoral-Program of the German Academic Exchange Service, DAAD (N.P.), the South Africa Research Chair for Mammal Behavioural Ecology (NCB), the Belgian co-operation service (DGD) at the Royal Museum for Central Africa (EG), and the Deanship of Scientific Research at the King Saud University through the research group project number RGP_020 (A.N.A., O.B.M.).http://www.elsevier.com/locate/jchemneu2017-03-31hb2016Mammal Research InstituteZoology and Entomolog

Orexinergic bouton density is lower in the cerebral cortex of cetaceans compared to artiodactyls

The species of the cetacean and artiodactyl suborders, which make up the cetartiodactyl order, have very different arousal thresholds and sleep-wake systems. The aim of this study was to determine whether cetaceans or artiodactyls have differently organized orexinergic arousal systems by examining the density of orexinergic innervation to the cerebral cortex. This study provides a comparison of orexinergic bouton density in the cerebral cortex of twelve cetartiodactyl species by means of immunohistochemical staining and stereological analysis. It was observed that the morphology of the axonal projections of the orexinergic system to the cerebral cortex was similar across all species, as the presence, size and proportion of large and small orexinergic boutons were similar. Despite this, orexinergic bouton density was lower in the cerebral cortex of cetaceans compared to artiodactyls, even when corrected for brain mass, neuron density, glial density and glial: neuron ratio. Glial density was identified as the major determinant for the observed differences. It appears a synergy exists between the orexinergic neurons and their projections, glial cells, and the biochemical correlates of appetitive drive and arousal, but further studies need to be performed to understand the full extent of the orexinergic system and its role in sustained arousal.This work was mainly supported by funding from the South African National Research Foundation (P.R.M., N.C.B.) and by a fellowship within the Postdoctoral-Program of the German Academic Exchange Service, DAAD (N.P.). The work was also supported by an IOER R&G Grant from Des Moines University (#12- 13-03) (M.A.S.), Reykjavik University 2010 Development Fund (K.Æ.K.), the Deanship of Scientific Research at the King Saud University through the research group project number RGP_020 (A.N.A., O.B.M.), and NIH grant DA 2R01MH064109 and the Department of Veterans Affairs (J.M.S).http://www.elsevier.com/locate/jchemneu2016-10-31hb2016Mammal Research InstituteZoology and Entomolog

Amplification of potential thermogenetic mechanisms in cetacean brains compared to artiodactyl brains

To elucidate factors underlying the evolution of large brains in cetaceans, we examined 16 brains from 14 cetartiodactyl species, with immunohistochemical techniques, for evidence of non-shivering thermogenesis. We show that, in comparison to the 11 artiodactyl brains studied (from 11 species), the 5 cetacean brains (from 3 species), exhibit an expanded expression of uncoupling protein 1 (UCP1, UCPs being mitochondrial inner membrane proteins that dissipate the proton gradient to generate heat) in cortical neurons, immunolocalization of UCP4 within a substantial proportion of glia throughout the brain, and an increased density of noradrenergic axonal boutons (noradrenaline functioning to control concentrations of and activate UCPs). Thus, cetacean brains studied possess multiple characteristics indicative of intensified thermogenetic functionality that can be related to their current and historical obligatory aquatic niche. These findings necessitate reassessment of our concepts regarding the reasons for large brain evolution and associated functional capacities in cetaceans.The South African National Research Foundation, a fellowship within the Postdoctoral-Program of the German Academic Exchange Service, International Scientific Partnership Program at King Saud University, the James S. McDonnell Foundation and the Swedish Research Council.https://www.nature.com/srepam2022Zoology and Entomolog

Olfaction based navigation in pigeons (Columba livia\textit {Columba livia})

Brieftauben haben die Fähigkeit, zu ihrem Taubenschlag zurück zu finden, nachdem sie Hunderte von Kilometeren entfernt freigelassen worden sind. Verhaltensstudien haben gezeigt, dass das olfaktorische System bei den Navigationsfähigkeiten der Taube eine wichtige Rolle spielt. Entsprechend der Theorie zu olfaktorischen Navigationskarte lernen Tauben eine Navigationskarte durch das Assoziieren verschiedener Düfte, die aus verschiedenen Windrichtungen mitgetragen werden. Manipulationen des olfaktorischen Systems stören das Heimfindevermögen der Taube. Bis heute sind jedoch die neuronalen Prozesse, die dem Heimfindevermögen zugrunde liegen könnten, weitgehend unbekannt. Ziel dieser Arbeit war es, diese neuronalen Prozesse zu untersuchen. Die Untersuchungsergebnisse haben gezeigt, dass das olfaktorische System die neuronale Grundlage für das Navigieren bildet, wobei das linke und das rechte olfaktorische System einen unterschiedlichen Beitrag für die Navigation zu leisten scheinen.Homing pigeons possess the ability to return to their home loft when displaced to an unfamiliar location up to hundreds of kilometres away. Behavioral studies have demonstrated that the olfactory system plays a key role in navigation ability in pigeons. According to the olfactory navigational map hypothesis, pigeons acquire a navigational map by associating different odours carried with winds from different directions. Consequently, any manipulation of the olfactory system would disrupt homing performance in pigeons. However, the neuronal processes underlying this navigation performance are still largely unknown. The aim of this thesis was to investigate the neuronal substrate underlying the behavioural data on olfactory-guided navigation in homing pigeons. Results show that the olfactory system may indeed serve as the neuronal substrate for navigation over an unfamiliar location. Additionally, the left and right olfactory systems contribute differently to the navigation process

Organisation and chemical neuroanatomy of the African elephant (Loxodonta africana) olfactory bulb

The olfactory system of mammals can be divided into a main and accessory olfactory system with initial processing for each system occurring in the olfactory bulb. The main and accessory olfactory bulbs have similar structural features, even though they appear to be functionally independent. In mammals the main olfactory bulb (MOB) is also one of two established sites of lifelong generation of new cells. The present study describes the histological and immunohistochemical neuroanatomy of the olfactory bulb of the African elephant (Loxodonta africana). The morphology of MOB of the elephant does not differ significantly from that described in other mammals; however, it lacks the internal plexiform layer. In addition, the glomeruli of the glomerular layer are organised in 2–4 “honey-combed” layers, a feature not commonly observed. The cell types and structures revealed with immunohistochemical stains (parvalbumin, calbindin, calretinin, tyrosine hydroxylase, orexin-A, glial fibrillary acidic protein) were similar to other mammals. Neurogenesis was examined using the neurogenic marker doublecortin. Migration of newly generated cells was observed in most layers of the MOB. No accessory olfactory bulb (AOB) was observed. Based on the general anatomy and the immunohistochemical observations, it is evident that the morphology of the African elephant MOB is, for the most part, similar to that of all mammals, although very large in absolute size

Neuropil Distribution In The Anterior Cingulate And Primary Visual Cortex Of Cetartiodactyla, Primates, and Afrotheria

Previous studies of the cerebral cortex have utilized the neuropil space as a proxy for connectivity, highlighting structural differences between cortical areas. The following study aims to investigate the distribution of neuropil space across 18 mammalian orders in two cortical areas, sampled from the frontal and occipital lobes. Results indicate a significant difference in neuropil space between cortical areas and species. The anterior cingulate cortex maintained a higher neuropil fraction than the primary visual cortex among all species studied.Drake University, College of Pharmacy and Health Sciences; School of Anatomical Sciences, The University of Witwatersrand, Johannesburg, South Africa; Department of Anatomy, Des Moines University, Des Moines, I

Fetal blockade of nicotinic acetylcholine transmission causes autism-like impairment of biological motion preference in the neonatal chick

Several environmental chemicals are suspected risk factors for autism spectrum disorder (ASD), including valproic acid (VPA) and pesticides acting on nicotinic acetylcholine receptors (nAChRs), if administered during pregnancy. However, their target processes in fetal neuro-development are unknown. We report that the injection of VPA into the fetus impaired imprinting to an artificial object in neonatal chicks, while a predisposed preference for biological motion (BM) remained intact. Blockade of nAChRs acted oppositely, sparing imprinting and impairing BM preference. Beside ketamine and tubocurarine, significant effects of imidacloprid (a neonicotinoid insecticide) appeared at a dose ≤1 ppm. In accord with the behavioral dissociations, VPA enhanced histone acetylation in the primary cell culture of fetal telencephalon, whereas ketamine did not. VPA reduced the brain weight and the ratio of NeuN-positive cells (matured neurons) in the telencephalon of hatchlings, whereas ketamine/tubocurarine did not. Despite the distinct underlying mechanisms, both VPA and nAChR blockade similarly impaired imprinting to biological image composed of point-light animations. Furthermore, both impairments were abolished by postnatal bumetanide treatment, suggesting a common pathology underlying the social attachment malformation. Neurotransmission via nAChR is thus critical for the early social bond formation, which is hindered by ambient neonicotinoids through impaired visual predispositions for animate objects