The diencephalon of two carnivore species: The feliform banded mongoose and the caniform domestic ferret.

This study provides an analysis of the cytoarchitecture, myeloarchitecture, and chemoarchitecture of the diencephalon (dorsal thalamus, ventral thalamus, and epithalamus) of the banded mongoose (Mungos mungo) and domestic ferret (Mustela putorius furo). Using architectural and immunohistochemical stains, we observe that the nuclear organization of the diencephalon is very similar in the two species, and similar to that reported in other carnivores, such as the domestic cat and dog. The same complement of putatively homologous nuclei were identified in both species, with only one variance, that being the presence of the perireticular nucleus in the domestic ferret, that was not observed in the banded mongoose. The chemoarchitecture was also mostly consistent between species, although there were a number of minor variations across a range of nuclei in the density of structures expressing the calcium-binding proteins parvalbumin, calbindin, and calretinin. Thus, despite almost 53 million years since these two species of carnivores shared a common ancestor, strong phylogenetic constraints appear to limit the potential for adaptive evolutionary plasticity within the carnivore order. Apart from the presence of the perireticular nucleus, the most notable difference between the species studied was the physical inversion of the dorsal lateral geniculate nucleus, as well as the lateral posterior and pulvinar nuclei in the domestic ferret compared to the banded mongoose and other carnivores, although this inversion appears to be a feature of the Mustelidae family. While no functional sequelae are suggested, this inversion is likely to result from the altricial birth of Mustelidae species.

Two different areas of the nucleus glomerulosus in the South American pufferfish, Colomesus asellus.

The nucleus glomerulosus (NG) in paracanthopterygian and acanthopterygian teleost fishes receives afferents from neurons of the nucleus corticalis (NC), whose dendrites extend to the layers, stratum fibrosum et griseum superficiale (SFGS) and stratum griseum centrale (SGC), of the tectum opticum. A re-examination in this study revealed, by means of tracer experiments using biotinylated dextran amine, a separation among both tectal layers, portions of the NC, and target areas in a laminated type of the NG in the South American pufferfish, Colomesus asellus. Neurons of the lateral part of the NC send their dendrites to the SFGS and project to an area located dorsolaterally and centrally in the NG. In contrast, dendrites from neurons of the medial part of the NC run to the SGC, and projections from these neurons terminate in the NG in an area extending from dorsomedial to ventrolateral in the outer portion. Therefore, these two areas in the NG receive input from different sources. The NG in the visual system of tetraodontids may be involved in higher cognitive functions requiring much energy, becoming apparent by its very high level of cytochrome c oxidase activity.

Neural origins of basal diencephalon in teleost fishes: Radial versus tangential migration.

Teleost fish possess large lateral diencephalic regions such as the torus lateralis, the preglomerular area, and the diffuse nucleus of the hypothalamic inferior lobe. While their developmental origins traditionally were suggested to lie in diencephalic midline ventricular proliferative zones, more remote midbrain origins were reported recently. This review focuses on the preglomerular region and summarizes the data supporting three existing hypotheses on its developmental origins. The conclusion is that lateral torus, diffuse nucleus of hypothalamic inferior lobe, and preglomerular region are part of the diencephalon, but have a multiregional origin provided by both radially and tangentially migrating cells forming these regions in question.

Untangling the dorsal diencephalic conduction system: a review of structure and function of the stria medullaris, habenula and fasciculus retroflexus.

The often-overlooked dorsal diencephalic conduction system (DDCS) is a highly conserved pathway linking the basal forebrain and the monoaminergic brainstem. It consists of three key structures; the stria medullaris, the habenula and the fasciculus retroflexus. The first component of the DDCS, the stria medullaris, is a discrete bilateral tract composed of fibers from the basal forebrain that terminate in the triangular eminence of the stalk of the pineal gland, known as the habenula. The habenula acts as a relay hub where incoming signals from the stria medullaris are processed and subsequently relayed to the midbrain and hindbrain monoaminergic nuclei through the fasciculus retroflexus. As a result of its wide-ranging connections, the DDCS has recently been implicated in a wide range of behaviors related to reward processing, aversion and motivation. As such, an understanding of the structure and connections of the DDCS may help illuminate the pathophysiology of neuropsychiatric disorders such as depression, addiction and pain. This is the first review of all three components of the DDCS, the stria medullaris, the habenula and the fasciculus retroflexus, with particular focus on their anatomy, function and development.

Comparative morphology and histology of the brain in Chinese toad ( Bufo gargarizans ) and chinese fire-billed newt ( Cynops orientalis ) / Morfología e histología comparada del cerebro en el sapo chino ( Bufo gargarizans ) y el tritón vientre de fuego chino ( Cynops orientalis )

The morphological and histological structure of the brains of Bufo gargarizans and Cynops orientalis were observed by anatomy and light microscopy. The results show that the brains of Bufo gargarizans and Cynops orientalis are divided into 5 parts which include the telencephalon, diencephalon, mesencephalon, cerebellum and medulla oblongata. The telencephalon consists of the olfactory bulb and the cerebral hemisphere. The olfactory bulb is developed that has two pairs of olfactory nerve. Bufo gargarizan has a symmetrical oval hemisphere optic lobes; Cynops orientalis only has a spherical optic lobe. The cerebellum is situated behind the optic lobe and closely connected with the myelencephalon. In this paper, the morphological and histological differences between the two species are discussed. The proportion of cerebral hemisphere is gradually increasing, which correlated with a progressive increase in the number of neuronal cell classes, and reflected in behavior complexity.

La estructura morfológica e histológica de los cerebros de Bufo gargarizans y Cynops orientalis se observó mediante anatomía y microscopía óptica. Los resultados muestran que los cerebros de Bufo gargarizans y Cynops orientalis se dividen en 5 partes, que incluyen el telencéfalo, diencéfalo, mesencéfalo, cerebelo y mielencéfalo. El telencéfalo consiste en bulbo olfatorio y hemisferio cerebral. El bulbo olfatorio tiene dos pares de nervios olfatorios. Los lóbulos ópticos de Bufo gargarizans son ovalados y simétricos en ambos hemisferios cerebrales; Cynops orientalis tiene solo un lóbulo óptico esférico. El cerebelo está situado detrás del lóbulo óptico y está estrechamente conectado con el mielencéfalo. En este trabajo, se discuten las diferencias morfológicas e histológicas entre las dos especies. El tamaño del hemisferio cerebral aumenta gradualmente, lo que se correlaciona con un aumento progresivo de células neuronales en los núcleos, reflejándose en la complejidad del comportamiento.

Distinctive expression pattern of Peg10 in the mouse brain

Peg10 (paternally expressed 10) is a retrotransposon-derived gene that is highly conserved across mammalian species. Peg10 is involved in cell proliferation and differentiation, and is essential for placenta formation in mice. Although a number of studies have examined Peg10 expression in the placenta, its cellular localization in the brain is still unclear. The function of Peg10 in the brain is also unknown. Here, we examined Peg10 distribution in the mouse brain. In situ hybridization revealed intense expression of the gene in the core region of the accumbens nucleus, lateral division of the bed nucleus of the stria terminalis, medial preoptic nucleus, paraventricular nucleus, arcuate nucleus, dorsomedial hypothalamic nucleus, premammillary nucleus, central amygdaloid nucleus and lateral parabrachial nucleus. Moderate to intense expression of Peg10 was also observed in monoaminergic nuclei such as the substantia nigra, dorsal raphe nucleus and locus coeruleus. These results suggest that Peg10 may play a role in motivational processes, emotional regulation, and autonomic functions in the brain. The findings also suggest that Peg10 may have contributed to the evolution of mammals, not only by participating in placenta formation, but also by regulating parental behavior and hormonal secretions necessary for maternal responsiveness

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The brain of the tree pangolin (Manis tricuspis). V. The diencephalon and hypothalamus.

The diencephalon (dorsal thalamus, ventral thalamus, and epithalamus) and the hypothalamus, play central roles in the processing of the majority of neural information within the central nervous system. Given the interactions of the diencephalon and hypothalamus with virtually all portions of the central nervous system, the comparative analysis of these regions lend key insights into potential neural, evolutionary, and behavioral specializations in different species. Here, we continue our analysis of the brain of the tree pangolin by providing a comprehensive description of the organization of the diencephalon and hypothalamus using a range of standard and immunohistochemical staining methods. In general, the diencephalon and hypothalamus of the tree pangolin follow the organization typically observed across mammals. No unusual structural configurations of the ventral thalamus, epithalamus, or hypothalamus were noted. Within the dorsal thalamus, the vast majority of typically identified nuclear groups and component nuclei were observed. The visual portion of the tree pangolin dorsal thalamus appears to be organized in a manner not dissimilar to that seen in most nonprimate and noncarnivore mammals, and lacks certain features that are present in the closely related carnivores. Within the ventral medial geniculate nucleus, a modular organization, revealed with parvalbumin neuropil immunostaining, is suggestive of specialized auditory processing in the tree pangolin. In addition, a potential absence of hypothalamic cholinergic neurons is suggestive of unusual patterns of sleep. These observations are discussed in an evolutionary and functional framework regarding the phylogeny and life history of the pangolins.

GABAergic modulation of olfactomotor transmission in lampreys.

Odor-guided behaviors, including homing, predator avoidance, or food and mate searching, are ubiquitous in animals. It is only recently that the neural substrate underlying olfactomotor behaviors in vertebrates was uncovered in lampreys. It consists of a neural pathway extending from the medial part of the olfactory bulb (medOB) to locomotor control centers in the brainstem via a single relay in the caudal diencephalon. This hardwired olfactomotor pathway is present throughout life and may be responsible for the olfactory-induced motor behaviors seen at all life stages. We investigated modulatory mechanisms acting on this pathway by conducting anatomical (tract tracing and immunohistochemistry) and physiological (intracellular recordings and calcium imaging) experiments on lamprey brain preparations. We show that the GABAergic circuitry of the olfactory bulb (OB) acts as a gatekeeper of this hardwired sensorimotor pathway. We also demonstrate the presence of a novel olfactomotor pathway that originates in the non-medOB and consists of a projection to the lateral pallium (LPal) that, in turn, projects to the caudal diencephalon and to the mesencephalic locomotor region (MLR). Our results indicate that olfactory inputs can induce behavioral responses by activating brain locomotor centers via two distinct pathways that are strongly modulated by GABA in the OB. The existence of segregated olfactory subsystems in lampreys suggests that the organization of the olfactory system in functional clusters may be a common ancestral trait of vertebrates.

An ontologically consistent MRI-based atlas of the mouse diencephalon.

In topological terms, the diencephalon lies between the hypothalamus and the midbrain. It is made up of three segments, prosomere 1 (pretectum), prosomere 2 (thalamus), and prosomere 3 (the prethalamus). A number of MRI-based atlases of different parts of the mouse brain have already been published, but none of them displays the segments the diencephalon and their component nuclei. In this study we present a new volumetric atlas identifying 89 structures in the diencephalon of the male C57BL/6J 12 week mouse. This atlas is based on an average of MR scans of 18 mouse brains imaged with a 16.4T scanner. This atlas is available for download at www.imaging.org.au/AMBMC. Additionally, we have created an FSL package to enable nonlinear registration of novel data sets to the AMBMC model and subsequent automatic segmentation.

Neurosurgical relevance of the dissection of the diencephalic white matter tracts using the Klingler technique.

OBJECTIVE: The Klingler fiber dissection technique is a relevant and reliable method for neurosurgery to identify with accuracy the fine structure of the brain anatomy highlighting white matter tracts. In order to demonstrate the significance of the application of this technique, we aimed to observe the course and relations of the mammillothalamic and habenulo-interpeduncular tracts as there are very few papers showing these important diencephalic tracts. MATERIAL AND METHODS: Twelve formalin-fixed brains were dissected using the Klingler technique in order to expose the medial diencephalic surface. Diencephalic white matter tracts, particularly the mammillothalamic and habenulo-interpeduncular tracts, were dissected using wooden spatulas and metallic dissectors with different sizes and tips. Several measurements were performed in both dissected hemispheres relative to the mammillothalamic and habenulo-interpeduncular tracts. RESULTS: The course and length of these two tracts were visualized and the relations with other fiber systems and with the neighboring gray matter structures quantified and registered. The mammillothalamic tract approximately marks the anteroposterior coordinate of the anterior pole of the subthalamic nucleus in the anterior commissure - posterior commissure plane. CONCLUSION: The present study helps to understand the three-dimensional architecture of the white matter systems of tracts when the Klingler technique is used. The numerical data obtained may be helpful to neurosurgeons while approaching brain paraventricular and ventricular lesions and deep brain stimulation. Finally, the anatomical knowledge can lower surgical complications and improve patient care particularly in the field of neurosurgery.

Diencephalic Size Is Restricted by a Novel Interplay Between GCN5 Acetyltransferase Activity and Retinoic Acid Signaling.

Diencephalic defects underlie an array of neurological diseases. Previous studies have suggested that retinoic acid (RA) signaling is involved in diencephalic development at late stages of embryonic development, but its roles and mechanisms of action during early neural development are still unclear. Here we demonstrate that mice lacking enzymatic activity of the acetyltransferase GCN5 ((Gcn5hat/hat )), which were previously characterized with respect to their exencephalic phenotype, exhibit significant diencephalic expansion, decreased diencephalic RA signaling, and increased diencephalic WNT and SHH signaling. Using a variety of molecular biology techniques in both cultured neuroepithelial cells treated with a GCN5 inhibitor and forebrain tissue from (Gcn5hat/hat ) embryos, we demonstrate that GCN5, RARα/γ, and the poorly characterized protein TACC1 form a complex in the nucleus that binds specific retinoic acid response elements in the absence of RA. Furthermore, RA triggers GCN5-mediated acetylation of TACC1, which results in dissociation of TACC1 from retinoic acid response elements and leads to transcriptional activation of RA target genes. Intriguingly, RA signaling defects caused by in vitro inhibition of GCN5 can be rescued through RA-dependent mechanisms that require RARß. Last, we demonstrate that the diencephalic expansion and transcriptional defects seen in (Gcn5hat/hat ) mutants can be rescued with gestational RA supplementation, supporting a direct link between GCN5, TACC1, and RA signaling in the developing diencephalon. Together, our studies identify a novel, nonhistone substrate for GCN5 whose modification regulates a previously undescribed, tissue-specific mechanism of RA signaling that is required to restrict diencephalic size during early forebrain development.SIGNIFICANCE STATEMENT Changes in diencephalic size and shape, as well as SNPs associated with retinoic acid (RA) signaling-associated genes, have been linked to neuropsychiatric disorders. However, the mechanisms that regulate diencephalic morphogenesis and the involvement of RA signaling in this process are poorly understood. Here we demonstrate a novel role of the acetyltransferase GCN5 in a previously undescribed mechanism of RA signaling in the developing forebrain that is required to maintain the appropriate size of the diencephalon. Together, our experiments identify a novel nonhistone substrate of GCN5, highlight an essential role for both GCN5 and RA signaling in early diencephalic development, and elucidate a novel molecular regulatory mechanism for RA signaling that is specific to the developing forebrain.

Conditional cell ablation via diphtheria toxin reveals distinct requirements for the basal plate in the regional identity of diencephalic subpopulations.

The mammalian diencephalon is the caudal derivative of the embryonic forebrain. Early events in diencephalic regionalization include its subdivision along the dorsoventral and anteroposterior axes. The prosomeric model by Puelles and Rubenstein (1993) suggests that the alar plate of the posterior diencephalon is partitioned into three different prosomeres (designated p1-p3), which develop into the pretectum, thalamus, and prethalamus, respectively. Here, we report the developmental consequences of genetic ablation of cell populations from the diencephalic basal plate. The strategy for conditionally regulated cell ablation is based on the targeted expression of the diphtheria toxin gene (DTA) to the diencephalic basal plate via tamoxifen- induced, Cre-mediated recombination of the ROSA(DTA) allele. We show that activation of DTA leads to specific cell loss in the basal plate of the posterior diencephalon, and disrupted early regionalization of distinct alar territories. In the basal plate-deficient embryos, the p1 alar plate exhibited reduced expression of subtype-specific markers in the pretectum, whereas p2 alar plate failed to further subdivide into two discrete thalamic subpopulations. We also show that these defects lead to abnormal nuclear organization at later developmental stages. Our data have implications for increased understanding of the interactive roles between discrete diencephalic compartments.

Functionally distinct amygdala subregions identified using DTI and high-resolution fMRI.

Although the amygdala is often directly linked with fear and emotion, amygdala neurons are activated by a wide variety of emotional and non-emotional stimuli. Different subregions within the amygdala may be engaged preferentially by different aspects of emotional and non-emotional tasks. To test this hypothesis, we measured and compared the effects of novelty and fear on amygdala activity. We used high-resolution blood oxygenation level-dependent (BOLD) imaging and streamline tractography to subdivide the amygdala into three distinct functional subunits. We identified a laterobasal subregion connected with the visual cortex that responds generally to visual stimuli, a non-projecting region that responds to salient visual stimuli, and a centromedial subregion connected with the diencephalon that responds only when a visual stimulus predicts an aversive outcome. We provide anatomical and functional support for a model of amygdala function where information enters through the laterobasal subregion, is processed by intrinsic circuits in the interspersed tissue, and is then passed to the centromedial subregion, where activation leads to behavioral output.

Catecholaminergic innervation of central and peripheral auditory circuitry varies with reproductive state in female midshipman fish, Porichthys notatus.

In seasonal breeding vertebrates, hormone regulation of catecholamines, which include dopamine and noradrenaline, may function, in part, to modulate behavioral responses to conspecific vocalizations. However, natural seasonal changes in catecholamine innervation of auditory nuclei is largely unexplored, especially in the peripheral auditory system, where encoding of social acoustic stimuli is initiated. The plainfin midshipman fish, Porichthys notatus, has proven to be an excellent model to explore mechanisms underlying seasonal peripheral auditory plasticity related to reproductive social behavior. Recently, we demonstrated robust catecholaminergic (CA) innervation throughout the auditory system in midshipman. Most notably, dopaminergic neurons in the diencephalon have widespread projections to auditory circuitry including direct innervation of the saccule, the main endorgan of hearing, and the cholinergic octavolateralis efferent nucleus (OE) which also projects to the inner ear. Here, we tested the hypothesis that gravid, reproductive summer females show differential CA innervation of the auditory system compared to non-reproductive winter females. We utilized quantitative immunofluorescence to measure tyrosine hydroxylase immunoreactive (TH-ir) fiber density throughout central auditory nuclei and the sensory epithelium of the saccule. Reproductive females exhibited greater density of TH-ir innervation in two forebrain areas including the auditory thalamus and greater density of TH-ir on somata and dendrites of the OE. In contrast, non-reproductive females had greater numbers of TH-ir terminals in the saccule and greater TH-ir fiber density in a region of the auditory hindbrain as well as greater numbers of TH-ir neurons in the preoptic area. These data provide evidence that catecholamines may function, in part, to seasonally modulate the sensitivity of the inner ear and, in turn, the appropriate behavioral response to reproductive acoustic signals.

The habenulo-interpeduncular and mammillothalamic tracts: early developed fiber tracts in the human fetal diencephalon.

PURPOSE: The habenulo-interpeduncular (HI) and mammillothalamic (MT) tracts are phylogenetically ancient. The clinical relevance of these tracts has recently received attention. In this work, we map the anatomy the developing HI and MT. METHODS: To investigate the topographical anatomy of developing fiber tracts in and around the diencephalon, we examined the horizontal, frontal, and sagittal serial paraffin sections of 28 human fetuses at 8-12 weeks of gestation. RESULTS: In all specimens, eosinophilic early fiber bundles were limited to the bilateral HI and MT tracts in contrast to pale-colored later developing fibers such as the thalamocortical projections and optic tract. The HI and MT tracts ran nearly parallel and sandwiched the thalamus from the dorsal and ventral sides, respectively. The nerve tract course appeared to range from 5-7 mm for the HI tract and 3-5 mm for the MT tract in 15 specimens at 11-12 weeks. The HI tract was embedded in, adjacent to, or distant from the developing parvocellular red nucleus. CONCLUSIONS: In early human fetuses, HI and MT tracts might be limited pathways for primitive cholinergic fiber connections between the ventral midbrain and epithalamic limbic system.

Development of the cerebellar afferent system in the shark Scyliorhinus canicula: insights into the basal organization of precerebellar nuclei in gnathostomes.

The cerebellum is recognized as an evolutionary innovation of jawed vertebrates, whose most primitive group is represented by the chondrichthyans, or cartilaginous fishes. A comprehensive knowledge of cerebellar connections in these fishes might shed light on the basal organization of the cerebellar system. Although the organization of the precerebellar system is known in adults, developmental studies are essential for understanding the origin and evolution of precerebellar nuclei. In the present work we performed a developmental study of cerebellar connections in embryos and juveniles of an advanced shark species, Scyliorhinus canicula, by application of tract tracing in combination with immunohistochemical techniques. Main precerebellar cell populations were located in the diencephalon (pretectum and thalamus), mesencephalon (reticular formation and nucleus ruber), rhombencephalon (cerebellar nucleus, reticular formation, and inferior olive), and spinal cord (ventral horn). The order of arrival of cerebellar afferent projections throughout development revealed a common pattern with other jawed vertebrates, which was helpful for comparison of stages of cerebellar development. The neurochemical study of the inferior olive and other precerebellar nuclei revealed many shared features with other gnathostomes. Furthermore, because many precerebellar nuclei originate from rhombic lips, the first analysis of neuronal migrations from these lips was performed with markers of neuroblasts. The shared features of development and organization of precerebellar connections observed between sharks and amniotes suggest that their basic pattern was established early in gnathostome evolution.

Architectural organization of the african elephant diencephalon and brainstem.

The current study examined the organization of the diencephalon and brainstem of the African elephant (Loxodonta africana) - a region of the elephant brain that has not been examined for at least 50 years. The current description, employing material amenable for use with modern neuroanatomical methods, shows that, for the most part, the elephant diencephalon and brainstem are what could be considered typically mammalian, with subtle differences in proportions and topology. The variations from these previous descriptions, where they occurred, were related to four specific aspects of neural information processing: (1) the motor systems, (2) the auditory and vocalization systems, (3) the orexinergic satiety/wakefulness centre of the hypothalamus and the locus coeruleus, and (4) the potential neurogenic lining of the brainstem. For the motor systems, three specific structures exhibited interesting differences in organization - the pars compacta of the substantia nigra, the facial motor nerve nucleus, and the inferior olivary nuclear complex, all related to the timing and learning of movements and likely related to the control of the trunk. The dopaminergic neurons of the substantia nigra appear to form distinct islands separated from each other by large fibre pathways, an appearance unique to the elephant. Each island may send topologically organized projections to the striatum forming a dopaminergic innervation mosaic that may relate to trunk movements. At least five regions of the combined vocalization production and auditory/seismic reception system were specialized, including the large and distinct nucleus ellipticus of the periaqueductal grey matter, the enlarged lateral superior olivary nucleus, the novel transverse infrageniculate nucleus of the dorsal thalamus, the enlarged dorsal column nuclei and the ventral posterior inferior nucleus of the dorsal thalamus. These specializations, related to production and reception of infrasound, allow the proposal of a novel concept regarding the reception and localization of infrasonic sources. The orexinergic system of the hypothalamus displayed a medial hypothalamic parvocellular cluster of neurons in addition to the magnocellular clusters typical of mammals located in the lateral hypothalamus, and a novel medial division of the locus coeruleus was observed in the pons. These systems are related to appetitive drive and promotion of wakefulness, two aspects of elephant behaviour that appear to be inextricably linked. Lastly, we observed an extensive potential neurogenic lining of the ventricles throughout the brainstem that is present in even quite old elephants, although the function of these cells remains elusive. These observations combined demonstrate that, while much of the elephant brainstem is typically mammalian, certain aspects of the anatomy related to specialized behaviour of elephants are present and instructive in understanding elephant behaviour.

Nucleus rostrolateralis: an expansion of the epithalamus in some actinopterygii.

The diencephalic nucleus rostrolateralis (RL) in the African butterfly fish (Pantodon buchholzi) is a brain nucleus identified in fewer than a dozen of the ∼25,000 species of actinopterygian fishes. Located in the rostrolateral diencephalon, this nucleus in Pantodon receives direct and indirect visual input from the superior visual field. Its lack of precedent or consistent phylogenetic expression creates a difficulty in interpreting the functional role of this nucleus within the visual system. By tracing experiments, RL was found to be afferent to nucleus interpeduncularis (IP) and the target of cells from the subpallium of the telencephalon. RL is a component of a descending telencephalic pathway involved in at least one behavior at the intersection of limbic and somatic activities--feeding. The parallelism between the ventral telencephalon--RL--IP and the limbic/striatal--habenula--IP pathway (the dorsal diencephalic conduction system, DDCS) suggests that RL is a component within the DDCS. Moreover, the hodological connections of RL suggest that RL is likely a hypertrophy of the lateral habenula.

Brain atlas of an emerging teleostean model: Nothobranchius furzeri.

Nothobranchius furzeri has emerged as a new fish model for neurobiological and age research over recent years, due to the exceptionally short lifespan, age-dependent cognitive/behavioral decline, expression of age-related biomarkers. The growing interest in this teleost has raised the need to construct an atlas of the whole brain of N. furzeri. The study has been carried out on adult specimens belonging to the long lived strain, originating from Mozambique and named MZM 04/10. In the atlas, the external features of brain, images of sections stained with luxol fast bleu/violet and schematic drawings of the most representative sections are showed. The identification and description of brain structures has been carried out on methodological and hodological studies. Comparative analyses have revealed remarkable and peculiar neuroanatomical characteristics of N. furzeri brain architecture. Thus, a comprehensive whole brain atlas of N. furzeri has been constructed aiming to provide a baseline for structural and functional future experiments on this emerging model organism.

Molecular characterization of prosomeric and intraprosomeric subdivisions of the embryonic zebrafish diencephalon.

During development of the early neural tube, positional information provided by signaling gradients is translated into a grid of transverse and longitudinal transcription factor expression domains. Transcription factor specification codes defining distinct histogenetic domains within this grid are evolutionarily conserved across vertebrates and may reflect an underlying common vertebrate bauplan. When compared to the rich body of comparative gene expression studies of tetrapods, there is considerably less comparative data available for teleost fish. We used sensitive multicolor fluorescent in situ hybridization to generate a detailed map of regulatory gene expression domains in the embryonic zebrafish diencephalon. The high resolution of this technique allowed us to resolve abutting and overlapping gene expression of different transcripts. We found that the relative topography of gene expression patterns in zebrafish was highly similar to those of orthologous genes in tetrapods and consistent with a three-prosomere organization of the alar and basal diencephalon. Our analysis further demonstrated a conservation of intraprosomeric subdivisions within prosomeres 1, 2, and 3 (p1, p2, and p3). A tripartition of zebrafish p1 was identified reminiscent of precommissural (PcP), juxtacommissural (JcP), and commissural (CoP) pretectal domains of tetrapods. The constructed detailed diencephalic transcription factor gene expression map further identified molecularly distinct thalamic and prethalamic rostral and caudal domains and a prethalamic eminence histogenetic domain in zebrafish. Our comparative gene expression analysis conformed with the idea of a common bauplan for the diencephalon of anamniote and amniote vertebrates from fish to mammals.