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Effects of voluntary ethanol consumption on emotional state and stress responsiveness in socially isolated rats
No full textSocial isolation of rats immediately after weaning is thought to represent an animal model of anxiety-like disorders. This mildly stressful condition reduces the cerebrocortical and plasma concentrations of 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) as well as increases the sensitivity of rats to the effects of acute ethanol administration on the concentrations of this neuroactive steroid. We further investigated the effects of voluntary consumption of ethanol at concentrations increasing from 2.5 to 10% over 4 weeks of isolation. Isolated rats showed a reduced ethanol preference compared with group-housed animals. Ethanol consumption did not affect the isolation-induced down-regulation of BDNF or Arc, but it attenuated the increase in the cerebrocortical concentration of 3α,5α-TH PROG induced by foot-shock stress in both isolated and group-housed animals as well as increased the percentage of number of entries made by socially isolated rats into the open arms in the elevated plus-maze test. Ethanol consumption did not affect expression of the α4 subunit of the GABA(A) receptor in the hippocampus of group-housed or isolated rats, whereas it up-regulated the δ subunit throughout the hippocampus under both conditions. The results suggest that low consumption of ethanol may ameliorate some negative effects of social isolation on stress sensitivity and behavior
Down-regulation of hippocampal BDNF and Arc associated with improvement in aversive spatial memory performance in socially isolated rats
No full textRats deprived of social contact with other rats at a young age experience a form of prolonged stress that leads to long-lasting changes in behavioral profile. Such isolation is thought to be anxiogenic for these normally gregarious animals, and the abnormal reactivity of isolated rats to environmental stimuli is thought to be a product of prolonged stress. We now show that isolation of rats at weaning reduced immobility time in the forced swim test, decreased sucrose intake and preference, and down-regulated both brain-derived neurotrophic factor (BDNF) and activity-regulated cytoskeletal associated protein (Arc) in the hippocampus. In the Morris water maze, isolated rats showed a reduced latency to reach the hidden platform during training, indicative of an improved learning performance, compared with group-housed rats. The cumulative search error during place training trials indicated a reliable difference between isolated and group-housed rats on days 4 and 5. The probe trial revealed a significant decrease of the average proximity to the target location in the isolated rats suggesting an improvement in spatial memory. Isolated rats also showed an increase in the plasma level of corticosterone on the 5th day of training and increased expression of BDNF and Arc in the hippocampus on both days 1 and 5. These results show that social isolation from weaning in rats results in development of depressive-like behavior but has a positive effect on spatial learning, supporting the existence of a facilitating effect of stress on cognitive functio
La separazione dalla prole reverte le modificazioni nell'espressione di BDNF, proteina Arc, spine dendritiche, LTP e neurogenesi osservate durante la gravidanza e dopo il parto
Get PDFLa gravidanza, il parto e il periodo post partum costituiscono particolari condizioni fisiologiche durante le quali il cervello femminile è sottoposto a modificazioni funzionali e morfologiche necessarie per l’insorgenza e il mantenimento del comportamento materno.
Il BDNF (Brain Derived Neurotrofic Factor), così come la proteina Arc (Activity-Regulated Cytoskeletal), costituisce un mediatore chiave della plasticità neuronale e la sua azione a lungo termine ha un ruolo importante nell’apprendimento, memoria, comportamento affettivo ed emozionale (1); entrambi inoltre sono in grado di regolare l’architettura neuronale (2).
Nel mio studio ho misurato le quantità di BDNF, di proteina Arc, la densità delle spine dendritiche (DSD), il potenziamento sinaptico a lungo termine (LTP) e la neurogenesi nell’ippocampo di femmine di ratto durante la gravidanza e dopo il parto. Inoltre ho valutato gli stessi parametri nelle madri private della prole una settimana dopo il parto.
Nel giro dentato i livelli di BDNF, Arc e DSD risultano essere aumentati al termine della gravidanza e durante l’allattamento, un effetto associato a un’incremento della LTP in confronto agli animali di controllo. La sottrazione della prole ha indotto una drastica riduzione dei livelli di BDNF, Arc e DSD, i cui valori sono scesi al di sotto dei livelli di controllo. Infine è stato osservato un incremento della neurogenesi al termine della gravidanza e in seguito alla sottrazione dei cuccioli e una riduzione durante l’allattamento.
La variazione dei livelli di espressione di BDNF e Arc, della DSD, i cambiamenti dell’LTP e della neurogenesi indotti dalla maternità e dalla separazione dei cuccioli possono avere un ruolo cruciale nella regolazione del comportamento materno.
------------------------------------------------------------------------------------------------------------------------Pregnancy, delivery and post partum period are among the most important physiological condition in which the brain of female undergo to the functional and morphological modification needed to adapt the behavior to the onset of motherhood.
Brain Derived Neurotrofic Factor (BDNF) is a key mediator of neuronal plasticity. Long term action of BDNF plays a key role in learning and memory, emotional and affective behaviour (1). Activity-regulated cytoskeleton-associated protein (Arc) also plays a relevant role in synaptic plasticity. A role for BDNF-Arc signalling in the regulation of neuronal architecture has been clearly demonstrated (2).
In my study the amount of BDNF, Arc protein, dendritic spines density (DSD), long term potentiation (LTP) and neurogenesis were measured in hippocampus of female rats during pregnancy and after delivery. The same parameters were also evaluated after delivery in the mothers deprived of their pups one week after birth.
In the dentate gyrus BDNF, Arc protein and DSD started to be markedly increased in the late pregnancy and during lactation, an effect associated to a significant increase of LTP and to a dramatic reduction of neurosteroid content compared to control rats. Separation of pups from their dams induced a marked reduction of DSD, BDNF and Arc protein, the amount of which felt at values markedly lower than control. Finally, we observed an increase of neurogenesis in the late pregnancy and after the separation of pups from their dams and a reduction during lactation.
The motherhood-induced change in the amount of DSD, BDNF, Arc, LTP and neurogenesis as well as the reversal by pups separation suggest a crucial role of neuronal plasticity in the regulation of maternal care. ---------------------------------------------------------------------------------------
1) Lu B. 2003, BDNF and activity-dependent synaptic modulation, Learn Mem.; 10(2):86-98.
2) Scharfman HE, Mercurio TC, Goodman JH, Wilson MA, MacLusky NJ 2003 Hippocampal excitability increases during the estrous cycle in the rat: a potential role for brain-derived neurotrophic factor, J Neurosci.;23(37):11641-52
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Enhanced Glutamatergic Synaptic Plasticity in the Hippocampal CA1 Field of Food-Restricted Rats: Involvement of CB1 Receptors
No full textThe endogenous endocannabinoid system has a crucial role in regulating appetite and feeding behavior in mammals, as well as working memory and reward mechanisms. In order to elucidate the possible role of cannabinoid type-1 receptors (CB1Rs) in the regulation of hippocampal plasticity in animals exposed to food restriction (FR), we limited the availability of food to a 2-h daily period for 3 weeks in Sprague-Dawley rats. FR rats showed a higher long-term potentiation at hippocampal CA1 excitatory synapses with a parallel increase in glutamate release when compared with animals fed ad libitum. FR rats showed a significant increase in the long-term spatial memory determined by Barnes maze. FR was also associated with a decreased inhibitory effect of the CB1R agonist win55,212-2 on glutamatergic field excitatory postsynaptic potentials, together with a decrease in hippocampal CB1R protein expression. In addition, hippocampal brain-derived neurotrophic factor protein levels and mushroom dendritic spine density were significantly enhanced in FR rats. Altogether, our data suggest that alterations of hippocampal CB1R expression and function in FR rats are associated with dendritic spine remodeling and functional potentiation of CA1 excitatory synapses, and these findings are consistent with increasing evidence supporting the idea that FR may improve cognitive functions.Neuropsychopharmacology advance online publication, 21 October 2015; doi:10.1038/npp.2015.280
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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