RESUMO
Precise control of neurite guidance during development is essential to ensure proper formation of neuronal networks and correct function of the central nervous system (CNS). How neuronal projections find their targets to generate appropriate synapses is not entirely understood. Although transcription factors are key molecules during neurogenesis, we do not know their entire function during the formation of networks in the CNS. Here, we used the Drosophila melanogaster optic lobe as a model for understanding neurite guidance during development. We assessed the function of Sox102F/SoxD, the unique Drosophila orthologue of the vertebrate SoxD family of transcription factors. SoxD is expressed in immature and mature neurons in the larval and adult lobula plate ganglia (one of the optic lobe neuropils), but is absent from glial cells, neural stem cells and progenitors of the lobula plate. SoxD RNAi knockdown in all neurons results in a reduction of the lobula plate neuropil, without affecting neuronal fate. This morphological defect is associated with an impaired optomotor response of adult flies. Moreover, knocking down SoxD only in T4/T5 neuronal types, which control motion vision, affects proper neurite guidance into the medulla and lobula. Our findings suggest that SoxD regulates neurite guidance, without affecting neuronal fate.
Assuntos
Proteínas de Drosophila/metabolismo , Rede Nervosa/metabolismo , Neuritos/metabolismo , Neurópilo/metabolismo , Fatores de Transcrição SOXD/metabolismo , Vias Visuais/metabolismo , Animais , Proteínas de Drosophila/genética , Drosophila melanogaster , Rede Nervosa/citologia , Neurópilo/citologia , Fatores de Transcrição SOXD/genética , Vias Visuais/citologiaRESUMO
Crustaceans are widely distributed and inhabit very different niches. Many of them are highly visual animals. Nevertheless, the neural composition of crustacean optic neuropils deeper than the lamina is mostly unknown. In particular, semiterrestrial crabs possess a highly developed visual system and display conspicuous visually guided behaviors. A previous study shows that the first optic neuropil, the lamina of the crab Neohelice granulata, possesses a surprisingly high number of elements in each cartridge. Here, we present a comprehensive description of individual elements composing the medulla of that same species. Using Golgi impregnation, we characterized a wide variety of cells. Only considering the class of transmedullary neurons, we describe over 50 different morphologies including small- and large-field units. Among others, we describe a type of centrifugal neuron hitherto not identified in other crustaceans or insects that probably feeds back information to every cartridge in the medulla. The possible functional role of such centrifugal elements is discussed in connection with the physiological and behavioral information on visual processing available for this crab. Taken together, the results reveal a very dense and complex neuropil in which several channels of information processing would be acting in parallel. We further examine our results considering the similarities and differences found between the layered organization and components of this crustacean medulla and the medullae of insects.
Assuntos
Braquiúros/anatomia & histologia , Bulbo/citologia , Neurônios/fisiologia , Neurópilo/citologia , Nervo Óptico/anatomia & histologia , Vias Visuais/fisiologia , Animais , Processamento de Imagem Assistida por Computador , Neurônios/ultraestrutura , Neurópilo/ultraestrutura , Coloração pela PrataRESUMO
Parkinson's disease is the second most prevalent neurodegenerative disease in the world. Its treatment is limited so far to the management of parkinsonian symptoms with L-DOPA (LD). The long-term use of LD is limited by the development of L-DOPA-induced dyskinesias and dystonia. However, recent studies have suggested that pharmacological targeting of the endocannabinoid system may potentially provide a valuable therapeutic tool to suppress these motor alterations. In the present study, we have explored the behavioral (L-DOPA-induced dyskinesias severity) and cytological (substantia nigra compacta neurons and striatum neuropil preservation) effects of the oral coadministration of LD and rimonabant, a selective antagonist of CB1 receptors, in the 6-hydroxydopamine rat model of Parkinson's disease. Oral coadministration of LD (30 mg/kg) and rimonabant (1 mg/kg) significantly decreased abnormal involuntary movements and dystonia, possibly through the conservation of some functional tyrosine hydroxylase-immunoreactive dopaminergic cells, which in turn translates into a well-preserved neuropil of a less denervated striatum. Our results provide anatomical evidence that long-term coadministration of LD with cannabinoid antagonist-based therapy may not only alleviate specific motor symptoms but also delay/arrest the degeneration of striatal and substantia nigra compacta cells.
Assuntos
Antagonistas de Receptores de Canabinoides/uso terapêutico , Di-Hidroxifenilalanina/administração & dosagem , Di-Hidroxifenilalanina/uso terapêutico , Discinesia Induzida por Medicamentos/tratamento farmacológico , Degeneração Neural/patologia , Transtornos Parkinsonianos/tratamento farmacológico , Piperidinas/uso terapêutico , Pirazóis/uso terapêutico , Administração Oral , Animais , Antagonistas de Receptores de Canabinoides/farmacologia , Corpo Estriado/citologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/ultraestrutura , Di-Hidroxifenilalanina/farmacologia , Modelos Animais de Doenças , Dopaminérgicos/administração & dosagem , Dopaminérgicos/farmacologia , Dopaminérgicos/uso terapêutico , Quimioterapia Combinada , Masculino , Degeneração Neural/tratamento farmacológico , Neurópilo/citologia , Oxidopamina , Transtornos Parkinsonianos/induzido quimicamente , Piperidinas/administração & dosagem , Piperidinas/farmacologia , Pirazóis/administração & dosagem , Pirazóis/farmacologia , Ratos , Rimonabanto , Substância Negra/citologia , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
The Decapoda is the largest order of crustaceans, some 10,000 species having been described to date. The order includes shrimps, lobsters, crayfishes, and crabs. Most of these are highly visual animals that display complex visually guided behaviors and, consequently, large areas of their nervous systems are dedicated to visual processing. However, our knowledge of the organization and functioning of the visual nervous system of these animals is still limited. Beneath the retina lie three serially arranged optic neuropils connected by two chiasmata. Here, we apply dye tracers in different areas of the retina or the optic neuropils to investigate the organization of visual space maps in the optic neuropils of the brachyuran crab Chasmagnathus granulatus. Our results reveal the way in which the visual space is represented in the three main optic neuropils of a decapod. We show that the crabs' optic chiasmata are oriented perpendicular to each other, an arrangement that seems to be unique among malacostracans. Crabs use retinal position in azimuth and elevation to categorize visual stimuli; for instance, stimuli moving above or below the horizon are interpreted as predators or conspecifics, respectively. The retinotopic maps revealed in the present study create the possibility of relating particular regions of the optic neuropils with distinct behavioral responses elicited by stimuli occurring in different regions of the visual field.
Assuntos
Braquiúros/anatomia & histologia , Braquiúros/fisiologia , Neurópilo/citologia , Lobo Óptico de Animais não Mamíferos/anatomia & histologia , Lobo Óptico de Animais não Mamíferos/fisiologia , Vias Visuais/anatomia & histologia , Animais , Masculino , Neurópilo/fisiologia , Campos Visuais/fisiologia , Vias Visuais/fisiologia , Percepção Visual/fisiologiaRESUMO
Crustaceans are among the most extensively distributed arthropods, occupying many ecologies and manifesting a great variety of compound eye optics; but in comparison with insects, relatively little is known about the organization and neuronal morphologies of their underlying optic neuropils. Most studies, which have been limited to descriptions of the first neuropil--the lamina--suggest that different species have approximately comparable cell types. However, such studies have been limited with regard to the types of neurons they identify and most omit their topographic relationships. It is also uncertain whether similarities, such as they are, are independent of visual ecologies. The present account describes and compares the morphologies and dispositions of monopolar and other efferent neurons as well as the organization of tangential and smaller centrifugal neurons in two grapsoid crabs, one from the South Atlantic, the other from the North Pacific. Because these species occupy significantly disparate ecologies we ask whether this might be reflected in differences of cell arrangements within the most peripheral levels of the visual system. The present study identifies such differences with respect to the organization of centrifugal neurons to the lamina. We also identify in both species neurons in the lamina that have hitherto not been identified in crustaceans and we draw specific comparisons between the layered organization of the grapsoid lamina and layered laminas of insects.
Assuntos
Braquiúros/anatomia & histologia , Rede Nervosa/anatomia & histologia , Neurônios , Neurópilo/citologia , Vias Visuais/citologia , Animais , Braquiúros/fisiologia , Masculino , Neurônios/fisiologia , Neurópilo/fisiologia , Especificidade da Espécie , Vias Visuais/anatomia & histologiaRESUMO
There is a mismatch between the documentation of the visually guided behaviors and visual physiology of decapods (Malacostraca, Crustacea) and knowledge about the neural architecture of their visual systems. The present study provides a description of the neuroanatomical features of the four visual neuropils of the grapsid crab Chasmagnathus granulatus, which is currently used as a model for investigating the neurobiology of learning and memory. Visual memory in Chasmagnathus is thought to be driven from within deep retinotopic neuropil by large-field motion-sensitive neurons. Here we describe the neural architecture characterizing the Chasmagnathus lobula, in which such neurons are found. It is shown that, unlike the equivalent region of insects, the malacostracan lobula is densely packed with columns, the spacing of which is the same as that of retinotopic units of the lamina. The lobula comprises many levels of strata and columnar afferents that supply systems of tangential neurons. Two of these, which are known to respond to movement across the retina, have orthogonally arranged dendritic fields deep in the lobula. They also show evidence of dye coupling. We discuss the significance of commonalties across taxa with respect to the organization of the lamina and medulla and contrasts these with possible taxon-specific arrangements of deeper neuropils that support systems of matched filters.
Assuntos
Braquiúros/anatomia & histologia , Percepção de Movimento/fisiologia , Neurópilo/citologia , Lobo Óptico de Animais não Mamíferos/citologia , Lobo Óptico de Animais não Mamíferos/fisiologia , Visão Ocular/fisiologia , Animais , Braquiúros/fisiologia , Masculino , Memória/fisiologia , Neurópilo/fisiologia , Vias Visuais/citologia , Vias Visuais/fisiologiaRESUMO
The mouse, like a few other rodent and marsupial species, displays a striking modular architecture in its primary somatosensory cortex (SI). These modules, known as barrels, are mostly defined by the peculiar arrangement of granule cells and thalamic axons in layer IV. In the present work, we studied both the distribution and morphology of neurons stained for NADPH diaphorase (NADPH-d) and neuropil reactivity in the posteromedial barrel subfield (PMBSF), which represents the mystacial whiskers. We then compared our results with previous descriptions of NADPH-d distribution in both neonatal and young mice. We found two types of neurons in the PMBSF: type I neurons, which have large cell bodies and are heavily stained by the NADPH-d reaction; and type II neurons, characterized by relatively small and poorly stained cell bodies. The distribution of type I cells in the PMBSF was not homogenous, with cells tending to concentrate in septa between barrels. Moreover, the cells found in septal region possess both a larger and more complex dendritic arborization than cells located inside barrels. Our findings are at variance with results from other groups that reported both an absence of type II cells and a homogeneous distribution of type I cells in the PMBSF of young animals. In addition, our results show a distribution of type I cells which is very similar to that previously described for the rat's barrel field.
Assuntos
NADPH Desidrogenase/metabolismo , Neurópilo/enzimologia , Neurônios Nitrérgicos/enzimologia , Córtex Somatossensorial/enzimologia , Vias Aferentes/fisiologia , Fatores Etários , Animais , Biomarcadores , Mapeamento Encefálico , Forma Celular/fisiologia , Dendritos/fisiologia , Dendritos/ultraestrutura , Histocitoquímica , Imuno-Histoquímica , Nervo Maxilar/fisiologia , Camundongos , NADPH Desidrogenase/análise , Neurópilo/citologia , Neurônios Nitrérgicos/classificação , Neurônios Nitrérgicos/citologia , Óxido Nítrico Sintase/análise , Óxido Nítrico Sintase/metabolismo , Córtex Somatossensorial/citologia , Vibrissas/fisiologiaRESUMO
The distribution of FMRFamide (FMRFa)-like immunoreactivity (LI) was studied in the brain and subesophageal ganglion of Triatoma infestans, the insect vector of Chagas' disease. The neuropeptide displayed a widespread distribution with immunostained somata in the optic lobe, in the anterior, lateral, and posterior soma rinds of the protocerebrum, and around the antennal sensory and mechanosensory and motor neuropils of the deutocerebrum. FMRFa-immunoreactive profiles of the subesophageal ganglion were seen in the mandibular, maxillary, and labial neuromeres. Immunostained neurites were detected in the medulla and lobula of the optic lobe, the lateral protocerebral neuropil, the median bundle, the calyces and the stalk of the mushroom bodies, and the central body. In the deutocerebrum, the sensory glomeruli showed a higher density of immunoreactive processes than the mechanosensory and motor neuropil, whereas the neuropils of each neuromere of the subesophageal ganglion displayed a moderate density of immunoreactive neurites. Colocalization of FMRFa-LI and crustacean pigment-dispersing hormone-LI was found in perikarya of the proximal optic lobe, the lobula, the sensory deutocerebrum, and the labial neuromere of the subesophageal ganglion. The distribution pattern of small cardioactive peptide B (SCP(B))-LI was also widespread, with immunolabeled somata surrounding every neuropil region of the brain and subesophageal ganglion, except for the optic lobe. FMRFa- and SCP(B)-LIs showed extensive colocalization in the brain of this triatomine species. The presence of immunolabeled perikarya displaying either FMRFa- or SCP(B)-LI confirmed that each antisera identified different peptide molecules. The distribution of FMRFa immunostaining in T. infestans raises the possibility that FMRFa plays a role in the regulation of circadian rhythmicity. The finding of immunolabeling in neurosecretory somata of the protocerebrum suggests that this neuropeptide may also act as a neurohormone.
Assuntos
Encéfalo/metabolismo , FMRFamida/metabolismo , Gânglios dos Invertebrados/metabolismo , Hormônios de Inseto/metabolismo , Neurônios/metabolismo , Triatoma/metabolismo , Animais , Encéfalo/citologia , Gânglios dos Invertebrados/citologia , Hormônios/metabolismo , Imuno-Histoquímica , Hormônios de Invertebrado/metabolismo , Masculino , Corpos Pedunculados/citologia , Corpos Pedunculados/metabolismo , Neuropeptídeos/metabolismo , Neurópilo/citologia , Neurópilo/metabolismo , Sistemas Neurossecretores/metabolismo , Lobo Óptico de Animais não Mamíferos/citologia , Lobo Óptico de Animais não Mamíferos/metabolismo , Especificidade de Órgãos , Precursores de Proteínas/metabolismo , Triatoma/citologiaRESUMO
The distribution of NADPH diaphorase (NADPH-d)/nitric oxide synthase (NOS) neurons was evaluated during the postnatal development of the primary somatosensory cortex (SI) of the rat. Both cell counts and area measurements of barrel fields were carried out throughout cortical maturation. In addition, NADPH-d and cytochrome oxidase (CO) activities were also compared in both coronal and tangential sections of rat SI between postnatal days (P) 10 and 90. Throughout this period, the neuropil distributions of both enzymes presented a remarkable similarity and have not changed noticeably. Their distribution pattern show the PMBSF as a two-compartmented structure, displaying a highly reactive region (barrel hollows) flanked by less reactive regions (barrel septa). The number of NADPH-d neurons increased significantly in the barrel fields between P10 and P23, with peak at P23. The dendritic arborization of NADPH-d neurons became more elaborated during barrel development. In all ages evaluated, the number of NADPH-d cells was always higher in septa than in the barrel hollows. Both high neuropil reactivity and differential distribution of NADPH-d neurons during SI development suggest a role for nitric oxide throughout barrel field maturation.
Assuntos
NADPH Desidrogenase/metabolismo , Neurônios/enzimologia , Córtex Somatossensorial/enzimologia , Córtex Somatossensorial/crescimento & desenvolvimento , Fatores Etários , Animais , Animais Recém-Nascidos , Contagem de Células , Diferenciação Celular/fisiologia , Tamanho Celular/fisiologia , Dendritos/enzimologia , Dendritos/ultraestrutura , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Neurônios/citologia , Neurópilo/citologia , Neurópilo/enzimologia , Neurônios Nitrérgicos/citologia , Neurônios Nitrérgicos/enzimologia , Óxido Nítrico Sintase/metabolismo , Ratos , Ratos Wistar , Córtex Somatossensorial/citologia , Regulação para Cima/fisiologia , Vibrissas/inervação , Vibrissas/fisiologiaRESUMO
The distribution of serotonin was studied in the Triatoma infestans central nervous system by using immunocytochemistry. Serotonin immunoreactive cell bodies and fibers were observed in the brain, subesophageal ganglion, and thoracic ganglia. In the brain, serotonin-like immunoreactivity was detected in a limited number of somata, which gave rise to an extensive network of labeled neurites in patterned as well as in nonglomerular neuropils. Immunolabeled perikarya were observed in the optic lobe and in the anteromedial and caudolateral soma rinds of the protocerebrum. Deutocerebral immunoreactive somata were mainly found in the medial layer surrounding the antennal lobe glomeruli, as well as in relationship to the antennal mechanosensory and motor center. The subesophageal ganglion contained serotonin immunoreactive perikarya of variable sizes and moderate to low density of positive fibers. In the prothoracic ganglion, immunoreactive somata were detected near the cephalic connectives as well as in its caudal end. Serotonin immunoreactive somata and fibers were observed in the posterior ganglion of the thorax, with the abdominal neuromeres harboring the highest number of immunolabeled perikarya. These results show that there is a widespread unique serotonergic system in the CNS of Triatoma infestans and suggest that the indolamine could act as a neuromodulator or as a neurohormone.