Distribution and morphology of putative catecholaminergic and serotonergic neurons in the brain of the greater canerat, Thryonomys swinderianus

The distribution, morphology and nuclear subdivisions of the putative catecholaminergic and serotonergic systems within the brain of the greater canerat (sometimes spelt cane rat) were identified following immunohistochemistry for tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the complement of nuclear subdivisions of these systems when comparing those of the greater canerat with reports of these systems in other rodents. The greater canerat was chosen for investigation as it is a large rodent (around 2.7kg body mass) and has an average brain mass of 13.75g, more than five times larger than that of the laboratory rat. The greater canerats used in the present study were caught from the wild, which is again another contrast to the laboratory rat. While these differences, especially that of size, may lead to the prediction of significant differences in the nuclear complement of these systems, we found that all nuclei identified in both systems in the laboratory rat and other rodents in several earlier studies had direct homologs in the brain of the greater canerat. Moreover, there were no additional nuclei in the brain of the greater canerat that are not found in the laboratory rat or other rodents. It is noted that the locus coeruleus of the laboratory rat differs in appearance to that reported for several other rodent species. The greater canerat is phylogenetically distant from the laboratory rat, but still a member of the order Rodentia. Thus, changes in the nuclear organization of these systems appears to demonstrate a form of constraint related to the phylogenetic level of the order.     

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.     

Nuclear organization and morphology of cholinergic, putative catecholaminergic and serotonergic neurons in the brains of two species of African mole-rat

The distribution, morphology and nuclear subdivisions of the cholinergic, putative catecholaminergic and serotonergic systems within the brains of two species of African mole-rat (Cape dune mole-rat -Bathyergus suillus; highveld mole-rat -Cryptomys hottentotuspretoriae) 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 mole-rats to published studies of other rodents. The mole-rats used exhibit a major reduction of the visual system and live a subterranean lifestyle. These wild caught animals also have differing social systems, the Cape dune mole-rat is strictly solitary whereas the highveld mole-rat occurs in social familial units. While these differences, especially that of phenotype, may lead to the prediction of significant differences in the nuclear complement of these systems, we found that all nuclei identified in all three systems in the laboratory rat and other rodents had direct homologs in the brains of the mole-rats studied. There were no additional nuclei in the brains of the mole-rats that are not found in the laboratory rat or other rodents and vice versa. The mole-rats are phylogenetically distant from the laboratory rat, but are still part of the order Rodentia. We conclude that changes in the nuclear organization of the systems studied appear to demonstrate a form of constraint related to the phylogenetic level of the order.     

Nuclear organization of cholinergic,putative catecholaminergic and serotonergic nuclei in the brain of the eastern rock elephant shrew,Elephantulus myurus

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.     

Distribution and morphology of catecholaminergic and serotonergic neurons in the brain of the highveld gerbil,Tatera brantsii

The distribution, morphology and nuclear subdivisions of the putative catecholaminergic and serotonergic systems within the brain of the highveld gerbil were identified following immunohistochemistry for tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the complement of nuclear subdivisions of these systems when comparing those of the highveld gerbil with those of the laboratory rat. The highveld gerbil was chosen as it is relatively closely related to the laboratory rat, but the Gerbillinae and Murinae lineages diverged over 20 million years ago. Moreover, even though brain sizes are similar, the life history and phenotypes between these two species are substantially different. The gerbils used in the present study were caught from the wild, which is again another contrast to the laboratory rat. While these differences may lead to the prediction of significant differences in the nuclear complement of these systems, we found that all nuclei identified in both systems in the laboratory rat in several earlier studies had direct homologs in the brain of the highveld gerbil. Moreover, there were no additional nuclei in the brain of the highveld gerbil that are not found in the laboratory rat. The only discernable difference between the two species was a greater density and number of catecholaminergic neurons in the olfactory bulb of the highveld gerbil. Thus, the evolution of nuclear parcellation in these systems appears to demonstrate a form of phylogenetic constraint related to the order Rodentia.     

Distribution and morphology of catecholaminergic and serotonergic neurons in the brain of the highveld gerbil, Tatera brantsii

The distribution, morphology and nuclear subdivisions of the putative catecholaminergic and serotonergic systems within the brain of the highveld gerbil were identified following immunohistochemistry for tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the complement of nuclear subdivisions of these systems when comparing those of the highveld gerbil with those of the laboratory rat. The highveld gerbil was chosen as it is relatively closely related to the laboratory rat, but the Gerbillinae and Murinae lineages diverged over 20 million years ago. Moreover, even though brain sizes are similar, the life history and phenotypes between these two species are substantially different. The gerbils used in the present study were caught from the wild, which is again another contrast to the laboratory rat. While these differences may lead to the prediction of significant differences in the nuclear complement of these systems, we found that all nuclei identified in both systems in the laboratory rat in several earlier studies had direct homologs in the brain of the highveld gerbil. Moreover, there were no additional nuclei in the brain of the highveld gerbil that are not found in the laboratory rat. The only discernable difference between the two species was a greater density and number of catecholaminergic neurons in the olfactory bulb of the highveld gerbil. Thus, the evolution of nuclear parcellation in these systems appears to demonstrate a form of phylogenetic constraint related to the order Rodentia.     

Nuclear organization of cholinergic,catecholaminergic, serotonergic and orexinergic systems in the brain of the Tasmanian devil (Sarcophilus harrisii)

This study investigated the nuclear organization of four immunohistochemically identifiable neural systems (cholinergic, catecholaminergic, serotonergic and orexinergic) within the brains of three male Tasmanian devils (Sarcophilus harrisii), which had a mean brain mass of 11.6 g. We found that the nuclei generally observed for these systems in other mammalian brains were present in the brain of the Tasmanian devil. Despite this, specific differences in the nuclear organization of the cholinergic, catecholaminergic and serotonergic systems appear to carry a phylogenetic signal. In the cholinergic system, only the dorsal hypothalamic cholinergic nucleus could be observed, while an extra dorsal subdivision of the laterodorsal tegmental nucleus and cholinergic neurons within the gelatinous layer of the caudal spinal trigeminal nucleus were observed. Within the catecholaminergic system the A4 nucleus of the locus coeruleus complex was absent, as was the caudal ventrolateral serotonergic group of the serotonergic system. The organization of the orexinergic system was similar to that seen in many mammals previously studied. Overall, while showing strong similarities to the organization of these systems in other mammals, the specific differences observed in the Tasmanian devil reveal either order specific, or class specific, features of these systems. Further studies will reveal the extent of change in the nuclear organization of these systems in marsupials and how these potential changes may affect functionality.     

Distribution and morphology of cholinergic, catecholaminergic and serotonergic neurons in the brain of Schreiber's long-fingered bat, Miniopterus schreibersii

The current study describes the nuclear parcellation and neuronal morphology of the cholinergic, catecholaminergic and serotonergic systems within the brain of a representative species of microbat. While these systems have been investigated in detail in the laboratory rat, and examined in several other mammalian species, no chiropterans, to the author's knowledge, have been examined. Using immunohistochemical stains for choline-acetyltransferase, tyrosine hydroxylase and serotonin, we were able to observe and document these systems in relation to the cytoarchitecture. The majority of cholinergic nuclei typically found in mammals were evident in the microbat, however we could not find evidence for choline-acetyltransferase immunopositive neurons in the Edinger–Westphal nucleus, parabigeminal nucleus, and the medullary tegmental field, as seen in several other mammalian species. A typically mammalian appearance of the catecholaminergic nuclei was observed, however, the anterior hypothalamic groups (A15 dorsal and ventral), the dorsal and dorsal caudal subdivisions of the ventral tegmental area (A10d and A10dc), and the ventral (pars reticulata) substantia nigra (A9v) were not present. The serotonergic nuclei were similar to that reported in all eutherian mammalian species studied to date. The overall complement of nuclei of these systems in the microbat, while different to the species examined in other orders of mammals, resembles most closely the complement seen in earlier studies of insectivore species, and is clearly distinguished from that seen in rodents, carnivores and primates. This data is discussed in terms of the phylogenetic relationships of the chiropterans.     

Distribution and morphology of cholinergic,catecholaminergic and serotonergic neurons in the brain of Schreiber's long-fingered bat,Miniopterus schreibersii

The current study describes the nuclear parcellation and neuronal morphology of the cholinergic, catecholaminergic and serotonergic systems within the brain of a representative species of microbat. While these systems have been investigated in detail in the laboratory rat, and examined in several other mammalian species, no chiropterans, to the author's knowledge, have been examined. Using immunohistochemical stains for choline-acetyltransferase, tyrosine hydroxylase and serotonin, we were able to observe and document these systems in relation to the cytoarchitecture. The majority of cholinergic nuclei typically found in mammals were evident in the microbat, however we could not find evidence for choline-acetyltransferase immunopositive neurons in the Edinger–Westphal nucleus, parabigeminal nucleus, and the medullary tegmental field, as seen in several other mammalian species. A typically mammalian appearance of the catecholaminergic nuclei was observed, however, the anterior hypothalamic groups (A15 dorsal and ventral), the dorsal and dorsal caudal subdivisions of the ventral tegmental area (A10d and A10dc), and the ventral (pars reticulata) substantia nigra (A9v) were not present. The serotonergic nuclei were similar to that reported in all eutherian mammalian species studied to date. The overall complement of nuclei of these systems in the microbat, while different to the species examined in other orders of mammals, resembles most closely the complement seen in earlier studies of insectivore species, and is clearly distinguished from that seen in rodents, carnivores and primates. This data is discussed in terms of the phylogenetic relationships of the chiropterans.     

Nuclear parcellation of certain immunohistochemically identifiable neuronal systems in the midbrain and pons of the Highveld molerat (Cryptomys hottentotus)

The present paper details our findings following immunohistochemical examination of the midbrain and pons of the Highveld molerat (Cryptomys hottentotus) using antibodies for vesicular acetylcholine transporter (cholinergic neurons), tyrosine hydroxylase (dopaminergic and noradrenergic neurons), and serotonin (serotonergic neurons). The aim was to see if, in this microphthalmic rodent that lacks a distinct circadian rhythm, the nuclei involved in aspects of visual processing and the sleep-wake cycle exhibited specific loss or morphological alteration. For all of the neural systems investigated we found nuclei that can be considered direct homologues of those found in the laboratory rat. There was no specific loss of any nuclear group of any of the systems investigated, but there was significant reduction (as judged qualitatively) in the number of neurons in the visual associated nuclei. The fact that we could identify all nuclear groupings from three systems in this species is suggestive of an evolutionary constraint acting at the level of the organization of the neural system.     

Distribution of orexinergic neurons and their terminal networks in the brains of two species of African mole rats

The distribution of orexinergic cell bodies and terminal networks within the brains of two species of African mole rat (Cape-dune mole rat--Bathyergus suillus and highveld mole rat--Cryptomys hottentotus) were identified using immunohistochemistry for orexin-A. The aim of the study was to investigate possible differences in the nuclear complement and terminal distribution of this system by comparing those of the mole rats to published studies of other rodents and mammals. The wild-caught mole rats used in this study live a subterranean lifestyle and are well known for their regressed visual system, which may lead to the prediction of differences in the distribution of the cell bodies and the terminal networks; however, we found that both species of mole rat displayed orexinergic nuclei limited to the hypothalamus in regions similar to those previously reported for other rodent and mammalian species. No immunoreactive neurons could be identified, in either species of mole rat within the anterior hypothalamic paraventricular nucleus, as has been reported for Murid rodents. The terminal networks, while remaining similar between the species, are more strongly expressed in the Cape-dune mole rat than in the highveld mole rat.     

Three-dimensional computerised atlas of the rat brain stem precerebellar system: approaches for mapping, visualization, and comparison of spatial distribution data

Comparisons of microscopical neuroanatomic data from different experiments and investigators are typically hampered by the use of different section planes and dissimilar techniques for data documentation. We have developed a framework for visualization and comparison of section-based, spatial distribution data, in brain stem nuclei. This framework provides opportunities for harmonized data presentation in neuroinformatics databases. Three-dimensional computerized reconstructions of the rat brain stem and precerebellar nuclei served as a basis for establishing internal coordinate systems for the pontine nuclei and the precerebellar divisions of the sensory trigeminal nuclei. Coordinate based diagrams were used for presentation of experimental data (spatial distribution of labelled neurons and axonal plexuses) from standard angles of view. Each nuclear coordinate system was based on a cuboid bounding box with a defined orientation. The bounding box was size-adjusted to touch cyto- and myeloarchitectonically defined boundaries of the individual nuclei, or easily identifiable nearby landmarks. We exemplify the use of these internal coordinate systems with dual retrograde neural tracing data from pontocerebellar and trigeminocerebellar systems. The new experimental data were combined, in the same coordinate based diagrams, with previously published data made available via a neuroinformatics data repository (www.nesys.uio.no/Database, see also www.cerebellum.org). Three-dimensional atlasing, internal nuclear coordinate systems, and consistent formats for presentation of neuroanatomic data in web-based data repositories, offer new opportunities for efficient analysis and re-analysis of neuroanatomic data. Accepted: 14 June 2001     

Lack of relationship between cellular density and either capillary density or metabolic rate in different regions of the brain

Whereas a pronounced correlation exists between local cerebral glucose utilization (LCGU) and capillary density in different regions of the brain, it is not known whether these parameters also correlate with the overall density of nuclei (cellularity). Therefore, cellularity was determined by diamidino-phenylindol (DAPI) fluorescent staining of nuclei in acetone-fixed frozen sections of the rat brain. A comparison of the density of nuclei in different brain regions showed much less variation than that observed in LCGU and capillary density. No correlation was found between nuclear density and either LCGU or capillary densities. In conclusion the cellular density is not a determinant of variation in LCGU and capillary density.     

Localization of hypocretin-like immunoreactivity in the brain of the diurnal rodent, Arvicanthis niloticus

The neuropeptide hypocretin (HCRT, also called orexin) acts in the brain to increase arousal and inhibit REM sleep. There is also substantial evidence that disruption of the hypocretin system results in narcolepsy. The distribution of HCRT + fibers in nocturnal animals is consistent with its role in arousal; fibers are concentrated in brain areas important in arousal and the inhibition of REM sleep. The distribution of HCRT-like immunoreactive (HCRT +) cells and fibers has been described in nocturnal but not diurnal rodents. We therefore examined the anatomical distribution of HCRT + cells and fibers in the diurnal murid rodent Arvicanthis niloticus (unstriped Nile grass rat). Arvicanthis niloticus were perfused and brain sections were collected through the forebrain and midbrain and processed for HCRT immunocytochemistry. Hypocretin-like immunopositive cell bodies were located in the lateral hypothalamus, dorsomedial hypothalamus, and perifornical area. The densest staining for HCRT + neuronal fibers was seen in the paraventricular thalamic nucleus, the locus coeruleus, and the raphe nuclei. The distribution of HCRT + cells and fibers is consistent with that found in other rodents such as rats and Syrian hamsters. Although the pattern of HCRT-like immunostaining for cells and fibers is similar in nocturnal rodents and diurnal A. niloticus, it will be important to compare the pattern of HCRT release, as well as activity of HCRT cells, between nocturnal and diurnal species.     

Neuroglobin and Cytoglobin expression in the human brain

Neuroglobin and Cytoglobin are new members of the heme–globin family. Both globins are primarily expressed in neurons of the brain and retina. Neuroglobin and Cytoglobin have been suggested as novel therapeutic targets in various neurodegenerative diseases based on their oxygen binding and cell protecting properties. However, findings in Neuroglobin-deficient mice question the endogenous neuroprotective properties. The expression pattern of Neuroglobin and Cytoglobin in the rodent brain is also in contradiction to a major role of neuronal protection. In a recent study, Neuroglobin was ubiquitously expressed and up-regulated following stroke in the human brain. The present study aimed at confirming our previous observations in rodents using two post-mortem human brains. The anatomical localization of Neuroglobin and Cytoglobin in the human brain is much like what has been described for the rodent brain. Neuroglobin is highly expressed in the hypothalamus, amygdale and in the pontine tegmental nuclei, but not in the hippocampus. Cytoglobin is highly expressed in the habenula, hypothalamus, thalamus, hippocampus and the pontine tegmental nuclei. We only detected a low expression of Neuroglobin and Cytoglobin in the cerebral cortex, while no expression in the cerebellar cortex was detectable. We provide a neuroanatomical indication for a different role of Neuroglobin and Cytoglobin in the human brain.     

Organization of cholinergic,putative catecholaminergic and serotonergic nuclei in the diencephalon,mibrain and pons of sub-adult male giraffes

The current study describes the nuclear organization and neuronal morphology of the cholinergic, putative catecholaminergic and serotonergic systems within the diencephalon, midbrain and pons of the giraffe using immunohistochemistry for choline acetyltransferase, tyrosine hydroxylase and serotonin. The giraffe has a unique phenotype (the long neck), a large brain (over 500 g) and is a non-domesticated animal, while previous studies examining the brains of other Artiodactyls have all been undertaken on domesticated animals. The aim of the present study was to investigate possible differences in the nuclear organization and neuronal morphology of the above-mentioned systems compared to that seen in other Artiodactyls and mammals. The nuclear organization of all three systems within the giraffe brain was similar to that of other Artiodactyls. Some features of interest were noted for the giraffe and in comparison to other mammals studied. The cholinergic neuronal somata of the laterodorsal tegmental nucleus were slightly larger than those of the pedunculopontine tegmental nucleus, a feature not described in other mammals. The putative catecholaminergic system of the giraffe appeared to lack an A15 dorsal nucleus, which is commonly seen in other mammals but absent in the Artiodactyls, had a large and expanded substantia nigra pars reticulata (A9 ventral), a small diffuse portion of the locus coerueleus (A6d), an expansive subcoeruleus (A7sc and A7d), and lacked the A4 nucleus of the locus coeruleus complex. The nuclear organization of the serotonergic system of the giraffe was identical to that seen in all other eutherian mammals studied to date. These observations in the giraffe demonstrate that despite significant changes in life history, phenotype, brain size and time of divergence, species within the same order show the same nuclear organization of the systems investigated.     

Thalamic nuclei in the opossum Monodelphis domestica

We investigated nuclear divisions of the thalamus in the gray short-tailed opossum (Monodelphis domestica) to gain detailed information for further developmental and comparative studies. Nissl and myelin staining, histochemistry for acetylcholinesterase and immunohistochemistry for calretinin and parvalbumin were performed on parallel series of sections. Many features of the Monodelphis opossum thalamus resemble those in Didelphis and small eutherians showing no particular sensory specializations, particularly in small murid rodents. However, several features of thalamic organization in Monodelphis were distinct from those in rodents. In the opossum the anterior and midline nuclear groups are more clearly separated from adjacent structures than in eutherians. The dorsal lateral geniculate nucleus (LGNd) starts more rostrally and occupies a large part of the lateral wall of the thalamus. As in other marsupials, two cytoarchitectonically different parts, alpha and beta are discernible in the LGNd of the opossum. Each of them may be subdivided into two additional bands in acetylcholinesterase staining, while in murid rodents the LGNd consists of a homogeneous mass of cells. Therefore, differentiation of the LGNd of the Monodelphis opossum is more advanced than in murid rodents. The medial geniculate body consists of three nuclei (medial, dorsal and ventral) that are cytoarchitectonically distinct and stain differentially for parvalbumin. The relatively large size of the MG and LGNd points to specialization of the visual and auditory systems in the Monodelphis opossum. In contrast to rodents, the lateral dorsal and lateral posterior nuclei in the opossum are poorly differentiated cytoarchitectonically.     

Nuclear organization of some immunohistochemically identifiable neural systems in two species of the Euarchontoglires: A Lagomorph,Lepus capensis,and a Scandentia,Tupaia belangeri

The present study describes the organization of the nuclei of the cholinergic, catecholaminergic, serotonergic and orexinergic systems in the brains of two members of Euarchontoglires, Lepus capensis and Tupaia belangeri. The aim of the present study was to investigate the nuclear complement of these neural systems in comparison to previous studies on Euarchontoglires and generally with other mammalian species. Brains were coronally sectioned and immunohistochemically stained with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A. The majority of nuclei revealed in the current study were similar between the species investigated and to mammals generally, but certain differences in the nuclear complement highlight potential phylogenetic interrelationships within the Euarchontoglires and across mammals. In the northern tree shrew the nucleus of the trapezoid body contained neurons immunoreactive to the choline acetyltransferase antibody with some of these neurons extending into the lamellae within the superior olivary nuclear complex (SON). The cholinergic nature of the neurons of this nucleus, and the extension of cholinergic neurons into the SON, has not been noted in any mammal studied to date. In addition, cholinergic neurons forming the medullary tegmental field were also present in the northern tree shrew. Regarding the catecholaminergic system, the cape hare presented with the rodent specific rostral dorsal midline medullary nucleus (C3), and the northern tree shrew lacked both the ventral and dorsal divisions of the anterior hypothalamic group (A15v and A15d). Both species were lacking the primate/megachiropteran specific compact portion of the locus coeruleus complex (A6c). The nuclei of the serotonergic and orexinergic systems of both species were similar to those seen across most Eutherian mammals. Our results lend support to the monophyly of the Glires, and more broadly suggest that the megachiropterans are more closely related to the primates than are any other members of Euarchontoglires studied to date.