1,720,966 research outputs found
Baclofen antagonizes nicotine-, cocaine-, and morphine-induced dopamine release in the nucleus accumbens of rat
No full textEvidence recently provided has suggested a specific involvement of the GABAergic system in modulating positive reinforcing properties of several drugs of abuse through an action on mesolimbic dopaminergic neurons. The GABA(B) receptor agonist baclofen has been proposed as a potential therapeutic agent for the clinical treatment of several forms of drug addiction. In the present study, using the in vivo microdialysis technique, we investigated the effect of baclofen on nicotine, cocaine, and morphine-induced increase in extracellular dopamine (DA) levels in the shell of the nucleus accumbens, a brain area supposedly involved in the modulation of the central effects of several drugs of abuse, of freely moving rats. As expected, nicotine (0.6 mg/kg s.c.), morphine (5 mg/kg s.c.), and cocaine (7.5 mg/kg i.p.) administration in rats induced a marked increase in extracellular DA concentrations in the nucleus accumbens, reaching a maximum value of +205 +/- 8.4%, +300 +/- 22.2%, and +370 +/- 30.7%, respectively. Pretreatment with baclofen (1.25 and 2.5 mg/kg i.p.) dose-dependently reduced the nicotine-, morphine-, and cocaine-evoked DA release in the shell of the nucleus accumbens. Furthermore, baclofen alone did not elicit changes in basal DA extracellular levels up to 180 min. Taken together, our data are in line with previous reports demonstrating the ability of baclofen to modulate the mesolimbic DAergic transmission and indicate baclofen as a putative candidate in the pharmacotherapy of polydrug abuse. (C) 2003 Wiley-Liss, Inc
Different effects of morphine on extracellular dopamine and 5-Hydroxyindolacetic acid levels in dorsal striatum and nucleus accumbens of DBA/2J and C57BL/6J mice
No full textDopamine and serotonin release in dorsal striatum and nucleus accumbens is differentially modulated by morphine in DBA/2J and C57BL/6J mice
No full textNumerous studies have demonstrated that genetic factors significantly influence opioid ability to induce behavioral modification in mice. This differential sensitivity has been extensively studied, particularly in the DBA/2J and C57BL/6J strains. In the present study, using the "in vivo" microdialysis technique in these strains, we investigated the effect of morphine administration on the extracellular levels of dopamine (DA), serotonin (5-HT), and their metabolites in the nucleus accumbens and dorsal striatum-areas thought to be involved in morphine-induced locomotor hyperactivity. In the nucleus accumbens, morphine (20 mg/kg) significantly increased extracellular levels of DA in both strains. However, in dorsal striatum the morphine-induced increase of extracellular DA was lower in DBA/2J mice than in C57BL/6J. Moreover, morphine significantly stimulated 5-HT and 5-hydroxyindolacetic acid (5-HIAA) release both in nucleus accumbens and dorsal striatum of C57BL/6J mice, whereas it decreased 5-HT release without modifying 5-HIAA levels in DBA/2J mice. These results suggest that the different behavioral and biochemical responses to acute morphine described in these two strains could be mediated by different sensitivity of both the dopaminergic and the serotonergic 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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