Changes in concentrations of NMDA receptor subunit GluN2B, Arc and syntaxin-1 in dorsal hippocampus Schaffer collateral synapses in a rat learned helplessness model of depression

Major depressive disorder involves changes in synaptic structure and function, but the molecular underpinnings of these changes are still not established. In an initial pilot experiment, whole-brain synaptosome screening with quantitative western blotting was performed to identify synaptic proteins that may show concentration changes in a congenital rat learned helplessness model of depression. We found that the N-methyl-D-aspartate receptor (NMDAR) subunits GluN2A/GluN2B, activityregulated cytoskeleton-associated protein (Arc) and syntaxin-1 showed significant concentration differences between congenitally learned helpless (LH) and nonlearned helpless (NLH) rats. Having identified these three proteins, we then performed more elaborate quantitative immunogold electron microscopic analyses of the proteins in a specific synapse type in the dorsal hippocampus: the Schaffer collateral synapse in the CA1 region. We expanded the setup to include also unstressed wild-type (WT) rats. The concentrations of the proteins in the LH and NLH groups were compared to WT animals. In this specific synapse, we found that the concentration of NMDARs was increased in postsynaptic spines in both LH and NLH rats. The concentration of Arc was significantly increased in postsynaptic densities in LH animals as well as in presynaptic cytoplasm of NLH rats. The concentration of syntaxin-1 was significantly increased in both presynaptic terminals and postsynaptic spines in LH animals, while pre- and postsynaptic syntaxin-1 concentrations were significantly decreased in NLH animals. These protein changes suggest pathways by which synaptic plasticity may be increased in dorsal hippocampal Schaffer collateral synapses during depression, corresponding to decreased synaptic stability.publishedVersio

Increased metabolic activity in the septum and habenula during stress is linked to subsequent expression of learned helplessness behavior

Uncontrollable stress can have a profound effect on an organism's ability to respond effectively to future stressful situations. Behavior subsequent to uncontrollable stress can vary greatly between individuals, falling on a spectrum between healthy resilience and maladaptive learned helplessness. It is unclear whether dysfunctional brain activity during uncontrollable stress is associated with vulnerability to learned helplessness; therefore, we measured metabolic activity during uncontrollable stress that correlated with ensuing inability to escape future stressors. We took advantage of small animal positron emission tomography (PET) and 2-deoxy-2[(18)F]fluoro-D-glucose ((18)FDG) to probe in vivo metabolic activity in wild type Sprague Dawley rats during uncontrollable, inescapable, unpredictable foot-shock stress, and subsequently tested the animals response to controllable, escapable, predictable foot-shock stress. When we correlated metabolic activity during the uncontrollable stress with consequent behavioral outcomes, we found that the degree to which animals failed to escape the foot-shock correlated with increased metabolic activity in the lateral septum and habenula. When used a seed region, metabolic activity in the habenula correlated with activity in the lateral septum, hypothalamus, medial thalamus, mammillary nuclei, ventral tegmental area, central gray, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and rostromedial tegmental nucleus, caudal linear raphe, and subiculum transition area. Furthermore, the lateral septum correlated with metabolic activity in the preoptic area, medial thalamus, habenula, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and caudal linear raphe. Together, our data suggest a group of brain regions involved in sensitivity to uncontrollable stress involving the lateral septum and habenula

Neuroprotective function for ramified microglia in hippocampal excitotoxicity

<p>Abstract</p> <p>Background</p> <p>Most of the known functions of microglia, including neurotoxic and neuroprotective properties, are attributed to morphologically-activated microglia. Resting, ramified microglia are suggested to primarily monitor their environment including synapses. Here, we show an active protective role of ramified microglia in excitotoxicity-induced neurodegeneration.</p> <p>Methods</p> <p>Mouse organotypic hippocampal slice cultures were treated with <it>N</it>-methyl-D-aspartic acid (NMDA) to induce excitotoxic neuronal cell death. This procedure was performed in slices containing resting microglia or slices that were chemically or genetically depleted of their endogenous microglia.</p> <p>Results</p> <p>Treatment of mouse organotypic hippocampal slice cultures with 10-50 μM <it>N</it>-methyl-D-aspartic acid (NMDA) induced region-specific excitotoxic neuronal cell death with CA1 neurons being most vulnerable, whereas CA3 and DG neurons were affected less. Ablation of ramified microglia severely enhanced NMDA-induced neuronal cell death in the CA3 and DG region rendering them almost as sensitive as CA1 neurons. Replenishment of microglia-free slices with microglia restored the original resistance of CA3 and DG neurons towards NMDA.</p> <p>Conclusions</p> <p>Our data strongly suggest that ramified microglia not only screen their microenvironment but additionally protect hippocampal neurons under pathological conditions. Morphological activation of ramified microglia is thus not required to influence neuronal survival.</p

Herophilus and Erasistratus on the hēgemonikon

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this record.In Alexandria at some point in the early third century bc, Herophilus of Chalcedon identified the nerves as a distinct system within the body, traced their origins to the brain, and recognised their role in transmitting sensation and voluntary motion. His discovery was based on dissection and vivisection, not only of animals, but also of human beings. Herophilus’ younger contemporary Erasistratus also integrated these findings into his rather bolder physiology. The implications of this discovery were of course wide-ranging. From a modern perspective, it is now widely celebrated as having established, for the first time on something like a scientific basis, that the brain has more or less the functions that we now ascribe to it. Likewise, in antiquity, Galen relied heavily on Herophilus’ discovery in his proof that the rational soul is located in the brain. As we shall see, it also had an impact on Stoic psychology. What exactly Herophilus and Erasistratus saw as its implications, however, is a different question, and the difficulties in answering it are considerable given the state of the evidence

Theory and terminology of mixture in Galen

Das Thema der vorliegenden Dissertation ist die Theorie und Terminologie der Mischung nach Galen. Im ersten Teil, der sich aus den ersten zwei Hauptkapiteln zusammensetzt, werden die historischen und theoretischen Quellen für Galens Modell zur Mischung der Primärelemente (das Warme, das Kalte, das Trockene und das Feuchte) und sein System der neun Mischungen (acht schlechte Mischungen und eine gute Mischung, in der keine Qualität überwiegt). Im ersten Hauptkapitel illustriere ich im Gegensatz zu den bisherigen konträren wissenschaftlichen Meinungen, dass Galens Modell zur Mischung der Primärelemente eine klare innere Logik aufweist und von der peripatetischen Naturphilosophie des 2. Jahrhunderts unserer Zeitrechnung beeinflusst wird. Dabei entbehrt es keinesfalls des „archaischen“ hippokratischen Ansatzes. Im zweiten Hauptkapitel der Dissertation analysiere ich die historischen und theoretischen Quellen von Galens Theorie der neun Mischungen. Genauer gesagt zeige ich in diesem Kapitel auf, dass Galens Theorie im Gegensatz zu bisherigen Gelehrtenmeinungen nicht vollständig von dem System der neun Mischungen abhängt, das die Pneumatiker entwickelt haben. In der Tat beruht Galens Modell auf einer anderen – peripatetischen – Elementartheorie. Im Gegensatz zur pneumatischen Medizin ist dieses Modell der neun Mischungen in seinem allgemeinen Weltbild fest verankert. Im zweiten Teil dieser Dissertation, der dem dritten Hauptkapitel entspricht, setze ich mich mit Galens Terminologie der Mischung und genauer gesagt mit seiner Verwendung der Begriffe krasis und mixis auseinander. Im Gegensatz zu vorherigen wissenschaftlichen Arbeiten, die besagen, dass der Unterschied von den Bestandteilen abhänge (krasis wäre eine Mischung von Qualitäten, während mixis eine Mischung von Substanzen wäre), zeige ich, dass der Unterschied zwischen krasis und mixis in der Phase des Prozesses und in dem Grad der Wiedererkennbarkeit der Bestandteile liegt.The present dissertation aimed at studying the theory and the terminology of mixture in Galen. The first part, which is composed of the first two main chapters, intended to examine the historical and theoretical sources of Galen’s model of mixture of primary elements (the hot, the cold, the dry and the wet) and of its system of nine mixtures (eight bad mixtures and one good mixture, where no quality predominates). In the first main chapter, I illustrated that, differently from the conflicting views expressed so far by the previous scholarship, Galen’s model of mixture of primary elements shows a clear internal logic and comes under the sway of the Peripatetic natural philosophy of the 2nd century CE, while in no way renouncing, on the other hand, the “archaic” Hippocratic background. In the second main chapter of the dissertation I analysed the historical and theoretical sources of Galen’s scheme of nine mixtures. More precisely, in this chapter we pointed out that, differently from what has been said by previous scholarship, although the Pneumatists developed a system of nine mixtures, Galen’s is not entirely dependent on it insofar as Galen’s relies on a different – Peripatetic – elemental theory and, differently from Pneumatic medicine, this scheme of nine mixtures is embedded in Galen’s general world view. In the second part of the thesis, which corresponds to the third main chapter, I have dealt with Galen’s terminology of mixture and, more precisely, with his usage of the terms krasis and mixis. Differently from the previous scholarship according to which the difference would depend on the constituents (krasis would be a mixture of qualities whereas mixis a mixture of substances), I have showed that the difference between krasis and mixis lies in the stage of the process and in the degree of recognisability of the constituents

Contemporâneo: mercado verde

Atualmente, somos bombardeados por informações de empresas, grifes e produtos que exploram ações ligadas à sustentabilidade, ecologia e preservação do meio ambiente. Essa verdadeira onda verde que envolve inúmeros setores, como a indústria da moda, ganha a cada dia mais e mais adeptos no mundo, sinalizando inclusive o surgimento de uma nova postura do consumidorque passa a não se importar em pagar um preço mais alto por determinados produtos que apresentam qualidade e valores que ultrapassam a própria moda. Percebemos também que empresas e consumidores olham para produtos focados na sustentabilidade, visando não só à preservação do planeta mas também à geração de novas oportunidades de negócios (...

Medial thalamic 18-FDG uptake following inescapable shock correlates with subsequent learned helpless behavior

The learned helplessness paradigm has been repeatedly shown to correlate with neurobiological aspects of depression in humans. In this model, rodents are exposed inescapable foot-shock in order to reveal susceptibility to escape deficit, defined as 'learned helplessness' (LH). Few methods are available to probe the neurobiological aspects underlying the differences in susceptibility in the living animal, thus far being limited to studies examining regional neurochemical changes with microdialysis. With the widespread implementation of small animal neuroimaging methods, including positron emission tomography (PET), it is now possible to explore the living brain on a systems level to define regional changes that may correlate with vulnerability to stress. In this study, 12 wild type Sprague-Dawley rats were exposed to 40 minutes of inescapable foot-shock followed by metabolic imaging using 2-deoxy-2[{sup 18}F]fluoro-D-glucose (18-FDG) 1 hour later. The escape test was performed on these rats 48 hours later (to accommodate radiotracer decay), where they were given the opportunity to press a lever to shut off the shock. A region of interest (ROI) analysis was used to investigate potential correlations (Pearson Regression Coefficients) between regional 18-FDG uptake following inescapable shock and subsequent learned helpless behavior (time to finish the test; number of successful lever presses within 20 seconds of shock onset). ROI analysis revealed a significant positive correlation between time to finish and 18-FDG uptake, and a negative correlation between lever presses and uptake, in the medial thalamic area (p=0.033, p=0.036). This ROI included the paraventricular thalamus, mediodorsal thalamus, and the habenula. In an effort to account for possible spillover artifact, the posterior thalamic area (including ventral medial and lateral portions) was also evaluated but did not reveal significant correlations (p=0.870, p=0.897). No other significant correlations were found in additional regions analyzed including the nucleus accumbens, caudate putamen, substantia nigra, and amygdala. These data suggest that medial thalamic 18-FDG uptake during inescapable shock may contribute to subsequent escape deficits, and are not confounded by shock effects per se, since all animals received the same treatment prior to scanning. We have previously explored 18-FDG differences following the escape test session which also showed hyperactivity in the medial thalamus of learned helpless animals compared to non-learned helpless, and included additional cortical-limbic changes. Given the neuroanatomical connections between the medial thalamus (and habenula) with the prefrontal cortex and monoaminergic brain stem, one possible speculation is that abnormal neuronal activity in these areas during stress may set in motion circuitry changes that correlate with learned helpless behavior

Cognitive aspects of congenital learned helplessness and its reversal by the monoamine oxidase (MAO)-B inhibitor deprenyl

Cognitive processes are assumed to change with learned helplessness, an animal model of depression, but little is known about such deficits. Here we investigated the role of cognitive and related functions in selectively bred helpless (cLH, n=10), non-helpless (cNLH, n=12) and wild type (WT, n=8) Sprague Dawley rats. The animals were exposed to an open field for 10min on each of two test days. On the third day, an object exploration paradigm was carried out. The animals were later tested for helplessness. Both cLH and cNLH rats were more active than WTs on the first day in the open field. Over trials, cNLH and WT rats lowered their activity less than cLH rats. This resistance-to-habituation co-varied with a resistance to develop helplessness. In cLH rats, higher 'anxiety' or less time spent in the center of the open field co-varied with severe helplessness. In WTs, a greater reactivity to novel objects and to a spatially relocated object predicted lower levels of helplessness. In cLH rats (n=4-5 per group), chronic treatment with a high dose of the monoamine oxidase (MAO)-B inhibitor deprenyl (10mg/kg; i.p.), an anti-Parkinson, nootropic and antidepressant drug, attenuated helplessness. Remarkably, helplessness reversal required the experience of repeated test trials, reminiscent of a learning process. Chronic deprenyl (10mg/kg; i.p.) did not alter locomotion/exploration or 'anxiety' in the open field. In conclusion, helplessness may be related to altered mechanisms of reinforcement learning and working memory, and to abnormalities in MAO-A and/or MAO-B functioning