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The caudolateral nidopallium (NCL, an analog of the prefrontal cortex) is known to be involved in learning, memory, and discrimination in corvids (a songbird), whereas the involvement of other brain regions in these phenomena is not well explored. We used house crows (Corvus splendens) to explore the neural correlates of learning and decision-making by initially training them on a shape discrimination task followed by immunohistochemistry to study the immediate early gene expression (Arc), a dopaminoceptive neuronal marker (DARPP-32, Dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa) to understand the involvement of the reward pathway and an immature neuronal marker (DCX, doublecortin) to detect learning-induced changes in adult neurogenesis. We performed neuronal counts and neuronal tracing, followed by morphometric analyses. Our present results have demonstrated that besides NCL, other parts of the caudal nidopallium (NC), avian basal ganglia, and intriguingly, vocal control regions in house crows are involved in visual discrimination. We have also found that training on the visual discrimination task can be correlated with neurite pruning in mature dopaminoceptive neurons and immature DCX-positive neurons in the NC of house crows. Furthermore, there is an increase in the incorporation of new neurons throughout NC and the medial striatum which can also be linked to learning. For the first time, our results demonstrate that a combination of structural changes in mature and immature neurons and adult neurogenesis are linked to learning in corvids.
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The opioid system in the brain is responsible for processing affective states such as pain, pleasure, and reward. It consists of three main receptors, mu- (µ-ORs), delta- (δ-ORs), and kappa- (κ-ORs), and their ligands - the endogenous opioid peptides. Despite their involvement in the reward pathway, and a signaling mechanism operating in synergy with the dopaminergic system, fewer reports focus on the role of these receptors in higher cognitive processes. Whereas research on opioids is predominated by studies on their addictive properties and role in pain pathways, recent studies suggest that these receptors may be involved in learning. Rodents deficient in δ-ORs were poor at recognizing the location of novel objects in their surroundings. Furthermore, in chicken, learning to avoid beads coated with a bitter chemical from those without the coating was modulated by δ-ORs. Similarly, µ-ORs facilitate long term potentiation in hippocampal CA3 neurons in mammals, thereby having a positive impact on spatial learning. Whereas these studies have explored the role of opioid receptors on learning using reward/punishment-based paradigms, the role of these receptors in natural learning processes, such as vocal learning, are yet unexplored. In this review, we explore studies that have established the expression pattern of these receptors in different brain regions of birds, with an emphasis on songbirds which are model systems for vocal learning. We also review the role of opioid receptors in modulating the cognitive processes associated with vocalizations in birds. Finally, we discuss the role of these receptors in regulating the motivation to vocalize, and a possible role in modulating vocal learning.
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The endogenous opioid system is evolutionarily conserved across reptiles, birds and mammals and is known to modulate varied brain functions such as learning, memory, cognition and reward. To date, most of the behavioral and anatomical studies in songbirds have mainly focused on µ-opioid receptors (ORs). Expression patterns of δ-ORs in zebra finches, a well-studied species of songbird have not yet been reported, possibly due to the high sequence similarity amongst different opioid receptors. In the present study, a specific riboprobe against the δ-OR mRNA was used to perform fluorescence in situ hybridization (FISH) on sections from the male zebra finch brain. We found that δ-OR mRNA was expressed in different parts of the pallium, basal ganglia, cerebellum and the hippocampus. Amongst the song control and auditory nuclei, HVC (abbreviation used as a formal name) and NIf (nucleus interfacialis nidopallii) strongly express δ-OR mRNA and stand out from the surrounding nidopallium. Whereas the expression of δ-OR mRNA is moderate in LMAN (lateral magnocellular nucleus of the anterior nidopallium), it is low in the MSt (medial striatum), Area X, DLM (dorsolateral nucleus of the medial thalamus), RA (robust nucleus of the arcopallium) of the song control circuit and Field L, Ov (nucleus ovoidalis) and MLd (nucleus mesencephalicus lateralis, pars dorsalis) of the auditory pathway. Our results suggest that δ-ORs may be involved in modulating singing, song learning as well as spatial learning in zebra finches.
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Encéfalo/metabolismo , Pinzones/metabolismo , Receptores Opioides delta/metabolismo , Animales , Ganglios Basales/metabolismo , Cerebelo/metabolismo , Pinzones/fisiología , Hipocampo/metabolismo , Hibridación Fluorescente in Situ , Masculino , ARN Mensajero/metabolismo , Receptores Opioides delta/fisiología , Vocalización Animal/fisiologíaRESUMEN
Earlier evidence suggests that besides humans, some species of mammals and birds demonstrate visual self-recognition, assessed by the controversial "mark" test. Whereas, there are high levels of inter-individual differences amongst a single species, some species such as macaques and pigeons which do not spontaneously demonstrate mirror self-recognition (MSR) can be trained to do so. We were surprised to discover that despite being widely used as a model system for avian research, the performance of zebra finches (Taenopygia guttata) on the mark test had not been studied earlier. Additionally, we studied the behavioral responses of another species of passerine songbirds (Indian house crows; Corvus splendens) to a mirror and the MSR mark test. Although a small number of adult male zebra finches appeared to display heightened responses toward the mark while observing their reflections, we could not rule out the possibility that these were a part of general grooming rather than specific to the mark. Furthermore, none of the house crows demonstrated mark-directed behavior or increased self-exploratory behaviors when facing mirrors. Our study suggests that self-directed behaviors need to be tested more rigorously in adult male zebra finches while facing their reflections and these findings need to be replicated in a larger population, given the high degree of variability in mirror-directed behaviors.
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The organization of the anterior forebrain pathway (AFP) of songbirds important for context-dependent singing is similar to that of cortical basal ganglia loops (CBG) in mammals, which underlie motor behaviors including vocalization. Since different components of the AFP express high levels of µ-opioid receptors (µ-ORs) as do CBG loops, songbirds act as model systems to study the role of opioid modulation on vocalization and the motivation to sing. The AFP in songbirds includes the cortical/pallial region LMAN (lateral magnocellular nucleus of the anterior nidopallium) which projects to Area X, a nucleus of the avian basal ganglia. In the present study, microdialysis was used to infuse different doses of the opioid antagonist naloxone in LMAN of adult male zebra finches. Whereas all doses of naloxone led to significant decreases in the number of FD (female-directed) songs, only 100 and 200 ng/ml of naloxone affected their acoustic properties. The decrease in FD song was not accompanied by changes in levels of attention toward females or those of neurotransmitters (dopamine, glutamate, and GABA) in LMAN. An earlier study had shown that similar manipulations in Area X did not lead to alterations in the number of FD songs but had significantly greater effects on their acoustic properties. Taken together, our results suggest that there are reciprocal effects of OR modulation on cortical and basal ganglia components of the AFP in songbirds.
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Although the catecholaminergic circuitry in the zebra finch brain has been well studied, there is little information regarding the postsynaptic targets of dopamine. To answer this question, we looked at overall patterns of immunoreactivity for DARPP-32 (a dopamine and cAMP-regulated phosphoprotein, present mostly in dopaminoceptive neurons) in adult male zebra finches. Our results demonstrated that as in mammals and other avian species, DARPP-32 expression was highest in both medial and lateral striatum. Interestingly, a specific pattern of immunoreactivity was observed in the song control system, with 'core' song control regions, that is, LMANcore (lateral magnocellular nucleus of the anterior nidopallium), RA (nucleus robustus arcopallialis) and HVC being less immunoreactive for DARPP-32 than 'shell' areas such as LMANshell, RAcup, AId (intermediate arcopallium) and HVCshelf. Our results suggest that whereas dopamine may modulate the shell pathways at various levels of the AFP, dopaminergic modulation of the core pathway occurs mainly through Area X, a basal ganglia nucleus. Further, secondary sensory cortices including the perientopallial belt, Fields L1 and L3 had higher DARPP-32-immunoreactivity than primary sensory cortical areas such as the pallial basolateral nucleus, entopallium proper and Field L2, corresponding to somatosensory, visual and auditory systems, respectively. We also found DARPP-32-rich axon terminals surrounding dopaminergic neurons in the ventral tegmental area-substantia nigra complex which in turn project to the striatum, suggesting that there may be a reciprocal modulation between these regions. Overall, DARPP-32 expression appears to be higher in areas involved in integrating sensory information, which further supports the role of this protein as a molecular integrator of different signal processing pathways.
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Encéfalo/metabolismo , Fosfoproteína 32 Regulada por Dopamina y AMPc/análisis , Pinzones/metabolismo , Neuronas/metabolismo , Animales , Cuerpo Estriado/metabolismo , Fosfoproteína 32 Regulada por Dopamina y AMPc/metabolismo , Neuronas Dopaminérgicas/metabolismo , Globo Pálido/metabolismo , Masculino , Vías Nerviosas/metabolismo , Prosencéfalo/metabolismoRESUMEN
Although the interplay between endogenous opioids and dopamine (DA) in the basal ganglia (BG) is known to underlie diverse motor functions, few studies exist on their role in modulating speech and vocalization. Vocal impairment is a common symptom of Parkinson's disease (PD), wherein DA depletion affects striosomes rich in µ-opioid receptors (µ-ORs). Symptoms of opioid addiction also include deficiencies in verbal functions and speech. To understand the interplay between the opioid system and BG in vocalization, we used adult male songbirds wherein high levels of µ-ORs are expressed in Area X, a BG region which is part of a circuit similar to the mammalian thalamocortical-basal ganglia loop. Changes in DA, glutamate and GABA levels were analyzed during the infusion of different doses of the µ-OR antagonist naloxone (50 and 100 ng/ml) specifically in Area X. Blocking µ-ORs in Area X with 100 ng/ml naloxone led to increased levels of DA in this region without altering the number of songs directed toward females (FD). Interestingly, this manipulation also led to changes in the spectro-temporal properties of FD songs, suggesting that altered opioid modulation in the thalamocortical-basal ganglia circuit can affect vocalization. Our study suggests that songbirds are excellent model systems to explore how the interplay between µ-ORs and DA modulation in the BG affects speech/vocalization.
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Birds of the family Corvidae which includes diverse species such as crows, rooks, ravens, magpies, jays, and jackdaws are known for their amazing abilities at problem-solving. Since the catecholaminergic system, especially the neurotransmitter dopamine, plays a role in cognition, we decided to study the distribution of tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamines in the brain of house crows (Corvus splendens). We also studied the expression of DARPP-32 (dopamine and cAMP-regulated phosphoprotein), which is expressed in dopaminoceptive neurons. Our results demonstrated that as in other avian species, the expression of both TH and DARPP-32 was highest in the house crow striatum. The caudolateral nidopallium (NCL, the avian analogue of the mammalian prefrontal cortex) could be differentiated from the surrounding pallial regions based on a larger number of TH-positive "baskets" of fibers around neurons in this region and greater intensity of DARPP-32 staining in the neuropil in this region. House crows also possessed distinct nuclei in their brains which corresponded to song control regions in other songbirds. Whereas immunoreactivity for TH was higher in the vocal control region Area X compared to the surrounding MSt (medial striatum) in house crows, staining in RA and HVC was not as prominent. Furthermore, the arcopallial song control regions RA (nucleus robustus arcopallialis) and AId (intermediate arcopallium) were strikingly negative for DARPP-32 staining, in contrast to the surrounding arcopallium. Patterns of immunoreactivity for TH and DARPP-32 in "limbic" areas such as the hippocampus, septum, and extended amygdala have also been described.
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Encéfalo/metabolismo , Cuervos/metabolismo , Fosfoproteína 32 Regulada por Dopamina y AMPc/metabolismo , Tirosina 3-Monooxigenasa/metabolismo , Animales , Neuronas/metabolismoRESUMEN
BACKGROUND: Although genomic DNA isolation using the Chelex 100 resin is rapid and inexpensive, the DNA obtained by this method has a low concentration in solution and contains suspended impurities. The presence of debris in the DNA solution may result in degradation of DNA on long term storage and inhibition of the polymerase chain reaction. In order to remove impurities and concentrate the DNA in solution, we have introduced modifications in the existing DNA isolation protocol using Chelex-100. We used ammonium acetate to precipitate proteins and a sodium acetate- isopropanol mixture to pellet out DNA which was washed with ethanol. RESULTS: A pure DNA pellet that can be dissolved in water or Tris-EDTA buffer and stored for a long time at - 80 °C was obtained. We also observed a 20-fold change in the DNA concentration following precipitation and re-dissolution. CONCLUSION: Our method is different from other extraction methods since it uses non-toxic, easily available and inexpensive reagents as well as minimal amounts of blood or tissue samples for the DNA extraction process. Besides its use in sex determination and genotyping in lab animals as described in this paper, it may also have applications in forensic science and diagnostics such as the easy detection of pathogenic DNA in blood.
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We had earlier demonstrated a neurofilament-rich plexus of axons in the presumptive human auditory cortex during fetal development which became adult-like during infancy. To elucidate the origin of these axons, we studied the expression of the vesicular glutamate transporters (VGLUT) 1 and 2 in the human auditory cortex at different stages of development. While VGLUT-1 expression predominates in intrinsic and cortico-cortical synapses, VGLUT-2 expression predominates in thalamocortical synapses. Levels of VGLUT-2 mRNA were higher in the auditory cortex before birth compared to postnatal development. In contrast, levels of VGLUT-1 mRNA were low before birth and increased during postnatal development to peak during childhood and then began to decrease in adolescence. Both VGLUT-1 and VGLUT-2 proteins were present in the human auditory cortex as early as 15GW. Further, immunohistochemistry revealed that the supra- and infragranular layers were more immunoreactive for VGLUT-1 compared to that in Layer IV at 34GW and this pattern was maintained until adulthood. As for VGLUT-1 mRNA, VGLUT-1 synapses increased in density between prenatal development and childhood in the human auditory cortex after which they appeared to undergo attrition or pruning. The adult pattern of VGLUT-2 immunoreactivity (a dense band of VGLUT-2-positive terminals in Layer IV) also began to appear in the presumptive Heschl's gyrus at 34GW. The density of VGLUT-2-positive puncta in Layer IV increased between prenatal development and adolescence, followed by a decrease in adulthood, suggesting that thalamic axons which innervate the human auditory cortex undergo pruning comparatively late in development.
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Corteza Auditiva/crecimiento & desarrollo , Corteza Auditiva/metabolismo , Neuronas/citología , Sinapsis , Proteína 1 de Transporte Vesicular de Glutamato/metabolismo , Proteína 2 de Transporte Vesicular de Glutamato/metabolismo , Adolescente , Adulto , Niño , Preescolar , Femenino , Desarrollo Fetal , Edad Gestacional , Humanos , Lactante , Filamentos Intermedios/metabolismo , Masculino , Persona de Mediana Edad , ARN Mensajero/metabolismo , Sinaptotagmina I/metabolismo , Adulto JovenRESUMEN
Lafora disease (LD) is a teenage-onset inherited progressive myoclonus epilepsy characterized by the accumulations of intracellular inclusions called Lafora bodies and caused by mutations in protein phosphatase laforin or ubiquitin ligase malin. But how the loss of function of either laforin or malin causes disease pathogenesis is poorly understood. Recently, neuronatin was identified as a novel substrate of malin that regulates glycogen synthesis. Here we demonstrate that the level of neuronatin is significantly up-regulated in the skin biopsy sample of LD patients having mutations in both malin and laforin. Neuronatin is highly expressed in human fetal brain with gradual decrease in expression in developing and adult brain. However, in adult brain, neuronatin is predominantly expressed in parvalbumin-positive GABAergic interneurons and localized in their processes. The level of neuronatin is increased and accumulated as insoluble aggregates in the cortical area of LD brain biopsy samples, and there is also a dramatic loss of parvalbumin-positive GABAergic interneurons. Ectopic expression of neuronatin in cultured neuronal cells results in increased intracellular Ca(2+), endoplasmic reticulum stress, proteasomal dysfunction, and cell death that can be partially rescued by malin. These findings suggest that the neuronatin-induced aberrant Ca(2+) signaling and endoplasmic reticulum stress might underlie LD pathogenesis.
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Señalización del Calcio , Retículo Endoplásmico/metabolismo , Enfermedad de Lafora/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Adolescente , Adulto , Factores de Edad , Biopsia/métodos , Encéfalo/patología , Calcio/metabolismo , Proteínas Portadoras/genética , Niño , Humanos , Lactante , Persona de Mediana Edad , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteínas Tirosina Fosfatasas no Receptoras/genética , Transducción de Señal , Piel/patología , Transfección , Ubiquitina-Proteína LigasasRESUMEN
The regulation of cell proliferation in the external granular layer (EGL) of the developing cerebellum is important for its normal patterning. An important signal that regulates EGL cell proliferation is Sonic hedgehog (Shh). Shh is secreted by the Purkinje cells (PC) and has a mitogenic effect on the granule cell precursors of the EGL. Deregulation of Shh signaling has been associated with abnormal development, and been implicated in medulloblastomas, which are tumors that arise from the cerebellum. Given the importance of the Shh pathway in cerebellum development and disease, there has been no systematic study of its expression pattern during human cerebellum development. In this study, we describe the expression pattern of Shh, its receptor patched, smoothened, and its effectors that belong to the Gli family of transcription factors, during normal human cerebellum development from 10 weeks of gestational age, and in medulloblastomas that represents a case of abnormal cell proliferation in the cerebellum. This expression pattern is compared to equivalent stages in the normal development of cerebellum in mouse, as well as in tumors. Important differences between human and mouse that reflect differences in the normal developmental program between the 2 species are observed. First, in humans there appears to be a stage of Shh signaling within the EGL, when the PC are not yet the source of Shh. Second, unlike in the postnatal mouse cerebellum, expression of Shh in the PC in the postnatal human cerebellum is downregulated. Finally, medulloblastomas in the human but not in patched heterozygote mouse express Shh. These results highlight cross-species differences in the regulation of the Shh signaling pathway.
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Proliferación Celular , Cerebelo/metabolismo , Proteínas Hedgehog/metabolismo , Animales , Calbindinas , Neoplasias Cerebelosas/metabolismo , Neoplasias Cerebelosas/patología , Cerebelo/embriología , Cerebelo/crecimiento & desarrollo , Cerebelo/patología , Preescolar , Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Proteínas Hedgehog/genética , Humanos , Lactante , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Meduloblastoma/metabolismo , Meduloblastoma/patología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Receptores Patched , Células de Purkinje/metabolismo , Receptores de Superficie Celular/genética , Receptores de Superficie Celular/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Proteína G de Unión al Calcio S100/genética , Proteína G de Unión al Calcio S100/metabolismo , Transducción de Señal , Receptor Smoothened , Proteína con Dedos de Zinc GLI1 , Proteína Gli2 con Dedos de ZincRESUMEN
Neurofilament medium (NF-M) and heavy (NF-H) chain proteins have been used as markers for maturity in the developing brain since their accumulation in axons leads to an increase in conduction velocity. Earlier studies have demonstrated immunoreactivity of neurofilaments in Layer I of the human auditory cortex at 22 gestation weeks (GW), whereas that in other layers developed between 1 and 12 postnatal years, suggesting a gradual increase in the processing of sounds. However, third trimester fetuses and infants are fairly sophisticated in their ability to discern different aspects of complex sounds. Given these contradictory findings, we decided to study the expression of neurofilaments in human auditory cortex between 15 GW and adulthood. We found that mRNA and protein for both NF-M and NF-H were present in the presumptive human auditory cortex in the second trimester and during the postnatal period (1 year--adulthood). Axons in all layers of the auditory cortex were immunoreactive for neurofilaments by 25 GW and the density of the neurofilament-rich plexus in the cortical wall became adult-like during the first postnatal year in humans (9 postnatal months). Our results suggest that in terms of neurofilament expression, axons within the preterm human auditory cortex may be more mature than previously thought.
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Envejecimiento/metabolismo , Corteza Auditiva/crecimiento & desarrollo , Corteza Auditiva/metabolismo , Proteínas de Neurofilamentos/metabolismo , Adulto , Corteza Auditiva/patología , Autopsia , Axones/metabolismo , Axones/patología , Biomarcadores/metabolismo , Preescolar , Femenino , Feto/metabolismo , Feto/patología , Humanos , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , ARN Mensajero/metabolismo , Lóbulo Temporal/crecimiento & desarrollo , Lóbulo Temporal/metabolismo , Lóbulo Temporal/patologíaRESUMEN
A rapid growth in human cerebellar development occurs in the third trimester, which is impeded by preterm delivery. The goal of this study was to characterize the impact of preterm delivery on the developmental program of the human cerebellum. Still born infants, which meant that all development up to that age had taken place in-utero, were age paired with preterm delivery infants, who had survived in an ex-utero environment, which meant that their development had also taken place outside the uterus. The two groups were assessed on quantitative measures that included molecular markers of granule neuron, purkinje neuron and bergmann glia differentiation, as well as the expression of the sonic hedgehog signaling pathway, that is important for cerebellar growth. We report that premature birth and development in an ex-utero environment leads to a significant decrease in the thickness and an increase in the packing density of the cells within the external granular layer and the inner granular layer well, as a reduction in the density of bergmann glial fibres. In addition, this also leads to a reduced expression of sonic hedgehog in the purkinje layer. We conclude that the developmental program of the cerebellum is specifically modified by events that follow preterm delivery.
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Cerebelo/embriología , Cerebelo/crecimiento & desarrollo , Madurez de los Órganos Fetales , Trabajo de Parto Prematuro/fisiopatología , Cerebelo/metabolismo , Femenino , Edad Gestacional , Proteínas Hedgehog/metabolismo , Humanos , Inmunohistoquímica , Recién Nacido , Recien Nacido Prematuro , Neuroglía/metabolismo , Embarazo , Tercer Trimestre del Embarazo , Células de Purkinje/metabolismoRESUMEN
Besides modulating pain, stress, physiological functions, motivation, and reward, the opioid system has been implicated in developmental and adult mammalian neurogenesis and gliogenesis. In adult male songbirds including zebra finches, neurons generated from the ventricular zone (VZ) of the lateral ventricles are incorporated throughout the telencephalon, including the song control nuclei, HVC, and area X. Although the endogenous opioid met-enkephalin is present in neurons adjacent to the VZ and is upregulated in song control regions during singing, it is not known whether the opioid system can modulate adult neurogenesis/gliogenesis in zebra finches. We used quantitative RT-PCR and in situ hybridization to demonstrate that µ- and δ-opioid receptors are expressed by the VZ of adult male zebra finches. Treating cultured VZ cells from male birds with the opioid antagonist naloxone led to an increase in cell proliferation measured by 5-bromo-2-deoxyuridine incorporation, whereas administering met-enkephalin had the opposite effect, compared with saline-treated cultures. Systemically administering naloxone (2.5 mg/kg body wt) to adult male zebra finches for 4 d also led to a significant increase in cell proliferation in the ventral VZ of these birds, compared with saline-treated controls. Our results show that cell proliferation is augmented by naloxone in the VZ adjacent to the anterior commissure, suggesting that the endogenous opioids modulate adult neurogenesis/gliogenesis by inhibiting cell proliferation in songbirds.
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Proliferación Celular/efectos de los fármacos , Ventrículos Cerebrales/efectos de los fármacos , Encefalina Metionina/farmacología , Pájaros Cantores , Animales , Secuencia de Bases , Células Cultivadas , Ventrículos Cerebrales/metabolismo , Cartilla de ADN , Inmunohistoquímica , Hibridación Fluorescente in Situ , Masculino , Naloxona/farmacología , Neurogénesis/efectos de los fármacos , ARN Mensajero/genética , Receptores Opioides/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Endogenous opioids are known to modulate motivated behaviors. Male zebra finches produce a highly motivated behavior (directed song) to court females and also sing in isolation (undirected song). We found that adult male zebra finches sang significantly fewer directed and undirected songs after administration of low doses (2.5 mg/kg body weight) of the general opioid antagonist naloxone, even though the order of syllables in songs was not altered. Surprisingly, high doses of naloxone (10 mg/kg body weight) dramatically decreased the production of undirected songs but had no significant effects on directed songs. There were no changes in the number of calls during directed or undirected song, movement, stereotyped behaviors including pecking and preening, feeding or drinking behaviors after naloxone administration. We also found that treating zebra finches with naloxone led to a decrease in tonality (goodness of pitch), frequency and amplitude modulation and an increase in the length of intersyllable intervals. Our results suggest that the opioid system can differentially modulate directed and undirected song as well as the acoustic characteristics of birdsong, perhaps by acting on different components of the song control system.
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Analgésicos Opioides/metabolismo , Pinzones/fisiología , Preferencia en el Apareamiento Animal/efectos de los fármacos , Vocalización Animal/efectos de los fármacos , Animales , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Relación Dosis-Respuesta a Droga , Femenino , Masculino , Movimiento/efectos de los fármacos , Naloxona/farmacología , Antagonistas de Narcóticos/farmacología , Receptores Opioides mu/metabolismo , Análisis Espectral/métodos , Conducta Estereotipada/efectos de los fármacos , Testosterona/sangreRESUMEN
The opioid system is known to play a role in various aspects of learning and memory in diverse species of mammals and birds. Earlier studies have localized the endogenous opioids, met- and leu-enkephalin, in the song control regions of male zebra finches (Taenopygia guttata), a sexually dimorphic species of songbirds wherein only males sing. Recent research has shown that levels of enkephalin increase in some of the song control regions during singing and that blocking opioid receptors with the antagonist naloxone decreases the frequency of singing in songbirds. However, the distribution of receptors specific to the opioid system has not been studied in zebra finches. In the present study, we used reverse transcriptase PCR (RT-PCR) and quantitative real-time PCR (qRT-PCR) to demonstrate that the song control regions lateral magnocellular nucleus of the anterior nidopallium (LMAN), Area X, MSt (medial striatum), HVC and RA (robust nucleus of the arcopallium) expressed higher levels of mu-OR mRNA compared to delta-OR mRNA. In situ hybridization was used to demonstrate that neither LMAN nor Area X could be delineated from the surrounding brain regions [anterior nidopallium (ANP) and MSt, respectively], based on OR mRNA expression. However, HVC and RA neurons expressed marginally higher levels of mu-OR mRNA compared to the posterior nidopallium, which was confirmed by immunohistochemical localization. We also found that the dorsolateral subdivision of DLM (dorsolateral nucleus of the medial thalamus) demonstrated high levels of mu-OR immunoreactivity. Our results suggest that the ORs may be involved in modulating different aspects of vocalization and/or gating auditory input, as well as motor control.
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Química Encefálica/fisiología , Encéfalo/fisiología , Pinzones/fisiología , Receptores Opioides delta/biosíntesis , Receptores Opioides mu/biosíntesis , Vocalización Animal/fisiología , Animales , Western Blotting , Encéfalo/citología , Inmunohistoquímica , Hibridación in Situ , Hibridación Fluorescente in Situ , Masculino , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Recent research has documented the involvement of the endogenous opioid system in neural development, including neurogenesis and neuronal differentiation. However, the expression of opioid receptors (ORs) in different cell types of the human ventricular and subventricular zones (VZ and SVZ) has not been studied during early gestation. In the present study, we have used immunohistochemistry and quantified the results to demonstrate that the levels of delta- and mu-OR subtypes were high in the VZ and SVZ between 11 and 16 gestation weeks (GW) and decreased by 20GW. These results have also been confirmed by studying OR mRNA expression in the VZ and SVZ. Both delta- and mu-OR subtypes were expressed by multipotential stem cells, newly differentiated neurons and developing glial cells to different extents. However, migrating neurons expressed negligible levels of both OR subtypes. Our results suggest that the opioid system may affect cellular proliferation and/or differentiation of stem cells into neurons and glia during the first and second trimesters of gestation in humans. Since layers II and III of the cerebral cortex are being formed during the second trimester, their development is most likely affected by the opioid system mediated through delta- and mu-ORs.
Asunto(s)
Ventrículos Cerebrales/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Expresión Génica/fisiología , Neocórtex , Receptores Opioides delta/metabolismo , Receptores Opioides mu/metabolismo , Factores de Edad , Diferenciación Celular/fisiología , Proliferación Celular , Ventrículos Cerebrales/embriología , Feto , Humanos , Neocórtex/citología , Neocórtex/embriología , Neocórtex/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuroglía/metabolismo , Neuronas/metabolismo , Cambios Post Mortem , ARN Mensajero/metabolismo , Receptores Opioides delta/genética , Receptores Opioides mu/genética , Células Madre/fisiologíaRESUMEN
Parkinson's disease (PD), a neurodegenerative disorder, causes severe motor impairment due to loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). MPTP, a neurotoxin that causes dopaminergic cell loss in mice, was used in an animal model to study the pathogenic mechanisms leading to neurodegeneration. We observed the activation of apoptosis signal regulating kinase (ASK1, MAPKKK) and phosphorylation of its downstream targets MKK4 and JNK, 12 h after administration of a single dose of MPTP. Further, Daxx, the death-associated protein, translocated to the cytosol selectively in SNpc neurons seemingly due to MPTP mediated down-regulation of DJ-1, the redox-sensitive protein that binds Daxx in the nucleus. Coadministration of alpha-lipoic acid (ALA), a thiol antioxidant, abolished the activation of ASK1 and phosphorylation of downstream kinases, MKK4, and JNK and prevented the down-regulation of DJ-1 and translocation of Daxx to the cytosol seen after MPTP. ALA also attenuated dopaminergic cell loss in SNpc seen after subchronic MPTP treatment. Our studies demonstrate for the first time that MPTP triggers death signaling pathway by activating ASK1 and translocating Daxx, in vivo, in dopaminergic neurons in SNpc of mice and thiol antioxidants, such as ALA terminate this cascade and afford neuroprotection.
Asunto(s)
Antioxidantes/uso terapéutico , Antiparkinsonianos/uso terapéutico , Proteínas Portadoras/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , MAP Quinasa Quinasa Quinasa 5/metabolismo , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Intoxicación por MPTP/tratamiento farmacológico , Proteínas del Tejido Nervioso/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Proteínas Nucleares/metabolismo , Trastornos Parkinsonianos/tratamiento farmacológico , Sustancia Negra/efectos de los fármacos , Ácido Tióctico/uso terapéutico , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/farmacocinética , Acetilcisteína/farmacología , Alquinos/farmacología , Animales , Antioxidantes/farmacología , Antiparkinsonianos/farmacología , Biotransformación , Núcleo Celular/metabolismo , Proteínas Co-Represoras , Cistationina gamma-Liasa/antagonistas & inhibidores , Citosol/metabolismo , Dopamina/análisis , Evaluación Preclínica de Medicamentos , Complejo I de Transporte de Electrón/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Glutatión/análisis , Glicina/análogos & derivados , Glicina/farmacología , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , MAP Quinasa Quinasa 4/metabolismo , Intoxicación por MPTP/metabolismo , Masculino , Mesencéfalo/química , Ratones , Ratones Endogámicos C57BL , Chaperonas Moleculares , Neuronas/química , Neuronas/patología , Fármacos Neuroprotectores/farmacología , Proteínas Oncogénicas/biosíntesis , Proteínas Oncogénicas/genética , Trastornos Parkinsonianos/metabolismo , Peroxirredoxinas , Fosforilación , Proteína Desglicasa DJ-1 , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Transporte de Proteínas/efectos de los fármacos , Sustancia Negra/metabolismo , Ácido Tióctico/farmacologíaRESUMEN
Connections of representations of the teeth and tongue in primary somatosensory cortex (area 3b) and adjoining cortex were revealed in owl, squirrel, and marmoset monkeys with injections of fluorescent tracers. Injection sites were identified by microelectrode recordings from neurons responsive to touch on the teeth or tongue. Patterns of cortical label were related to myeloarchitecture in sections cut parallel to the surface of flattened cortex, and to coronal sections of the thalamus processed for cytochrome oxidase (CO). Cortical sections revealed a caudorostral series of myelin dense ovals (O1-O4) in area 3b that represent the periodontal receptors of the contralateral teeth, the contralateral tongue, the ipsilateral teeth, and the ipsilateral tongue. The ventroposterior medial subnucleus, VPM, and the ventroposterior medial parvicellular nucleus for taste, VPMpc, were identified in the thalamic sections. Injections placed in the O1 oval representing teeth labeled neurons in VPM, while injections in O2 representing the tongue labeled neurons in both VPMpc and VPM. These injections also labeled adjacent part of areas 3a and 1, and locations in the lateral sulcus and frontal lobe. Callosally, connections of the ovals were most dense with corresponding ovals. Injections in the area 1 representation of the tongue labeled neurons in VPMpc and VPM, and ipsilateral area 3b ovals, area 3a, opercular cortex, and cortex in the lateral sulcus. Contralaterally, labeled neurons were mostly in area 1. The results implicate portions of areas 3b, 3a, and 1 in the processing of tactile information from the teeth and tongue, and possibly taste information from the tongue.