1,720,965 research outputs found
Changes in brain dopamine and acetylcholine release during and following stress are independent of the pituitary-adrenocortical axis.
No full textMicrodialysis was employed to assess extracellular dopamine from medial prefrontal cortex, nucleus accumbens, nucleus caudatus, and acetylcholine from the hippocampus of conscious rats during and after 120 min restraint stress. Restraint stress rapidly stimulated the release and the metabolism of dopamine in the medial prefrontal cortex and in the nucleus accumbens, and acetylcholine release in the hippocampus. Fifty-sixty min later, although rats were still restrained, dopamine and acetylcholine release gradually returned to basal levels. When the animals were freed a considerable increase in the release of both neurotransmitters was observed. No changes in the striatum were observed throughout the experiments. The time-course of plasma corticosterone did not parallel that of dopamine and acetylcholine release, increasing during the whole stress procedure, and decreasing when the animals were released. Adrenalectomized rats responded to stress and liberation in much the same way as intact rats. The administration of exogenous corticosterone (0.5-1.5 mg/kg s.c.) did not change the release of dopamine from the prefrontal cortex and nucleus accumbens, and of acetylcholine from the hippocampus, while the dose of 3.0 mg/kg which stimulated them, raised plasma corticosterone to very high concentrations which had never been attained during stress. Moreover, RU 38486, an antagonist of brain glucocorticoid receptors, did not antagonize the stress-induced increase of neurotransmitter release
Muscarinic and nicotinic receptors and the function of the cholinergic synapse in the rat’s hippocampus: selective age dependent changes and therapeutic interventions.
No full textCortical and limbic dopamine and acetylcholine release as neurochemical correlates of emotional arousal in both aversive and non-aversive environmental changes.
No full textL-alpha-glycerylphosphorylcholine antagonizes scopolamine-induced amnesia and enhances hippocampal cholinergic transmission in the rat.
No full textThe effects of L-alpha-glycerylphosphorylcholine (alpha-GPC) on scopolamine-induced memory impairment and on brain acetylcholine (ACh) synthesis and release were investigated in rats. Oral administration of alpha-GPC 3 h before the behavioural test prevented the learning impairment induced by scopolamine given 30 min before the acquisition of a passive avoidance response. Similarly, retrograde amnesia induced by scopolamine, given immediately after acquisition training, was also completely reversed by the drug. These effects were dose-dependent with a maximum at 300 mg/kg. The mechanism of action of this compound was investigated by measuring hippocampal ACh synthesis and release both in vivo by means of the microdialysis technique and in vitro in tissue slices. alpha-GPC dose dependently increased ACh release with a maximum at 300 mg/kg. In addition, i.v. injection of [14C]alpha-GPC resulted in [14C]ACh formation. The data suggest that the behavioural effects of alpha-GPC may be related to its property to increase hippocampal ACh synthesis and release
REPEATED STRESSFUL EXPERIENCES DIFFERENTLY AFFECT LIMBIC DOPAMINE RELEASE DURING AND FOLLOWING STRESS
No full textThe effects of repeated restraint stress exposures (daily 60 min, for 6 days) on extracellular dopamine in the nucleus accumbens, during and after the stress experience, have been investigated in rats by in vivo microdialysis. On the first day, restraint increased dopamine release during the first 40 min followed by a return to basal levels (50-60 min later). As soon as restraint ceased and the rats were set free, there was another increase in dopamine release lasting 40 min. On the second and third day, restraint produced only a slight increase in dopamine release, while no significant changes were evident from the fourth to the sixth day. By contrast, from the second to the sixth day the increase in dopamine release observed once rats were freed, was unchanged in comparison to the first day. The present results show that the activation of the mesolimbic dopaminergic system induced by aversive stimuli adapts to repeated experiences differently from that produced by pleasurable events, suggesting that aversive and rewarding experiences involve different neural systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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