1,720,975 research outputs found
The corticotropin-releasing factor receptor-1 pathway mediates the negative affective states of opiate withdrawal.
No full textThe negative affective symptoms of opiate withdrawal powerfully motivate drug-seeking behavior and may trigger relapse to heroin abuse. To date, no medications exist that effectively relieve the negative affective symptoms of opiate withdrawal. The corticotropin-releasing factor (CRF) system has been hypothesized to mediate the motivational effects of drug dependence. The CRF signal is transmitted by two distinct receptors named CRF receptor-1 (CRF1) and CRF2. Here we report that genetic disruption of CRF1 receptor pathways in mice eliminates the negative affective states of opiate withdrawal. In particular, neither CRF1 receptor heterozygous (CRF1+/-) nor homozygous (CRF1-/-) null mutant mice avoided environmental cues repeatedly paired with the early phase of opiate withdrawal. These results were not due to altered associative learning processes because CRF1+/- and CRF1-/- mice displayed reliable, conditioned place aversions to environmental cues paired with the kappa-opioid receptor agonist U-50,488H. We also examined the impact of CRF1 receptor-deficiency upon opiate withdrawal-induced dynorphin activity in the nucleus accumbens, a brain molecular mechanism thought to underlie the negative affective states of drug withdrawal. Consistent with the behavioral indices, we found that, during the early phase of opiate withdrawal, neither CRF1+/- nor CRF1-/- showed increased dynorphin mRNA levels in the nucleus accumbens. This study reveals a cardinal role for CRF/CRF1 receptor pathways in the negative affective states of opiate withdrawal and suggests therapeutic strategies for the treatment of opiate addiction
Gender- and morphine dose-linked expression of spontaneous somatic opiate withdrawal in mice.
No full textThe opiate withdrawal syndrome powerfully motivates opiate seeking and abuse. Development of effective medications for opiate withdrawal symptoms is thus a primary research goal and heavily relies on improved experimental models. This study was carried out to establish a clinically relevant paradigm to assess somatic opiate withdrawal in mice. Female and male C57BL/6J mice were treated with saline or increasing morphine doses (10-50mg/kg or 20-100mg/kg) during 6 consecutive days and tested for the spontaneous expression of somatic opiate withdrawal signs 8, 32, 56 and 80 h after last drug administration. Contrary to opioid receptor antagonist-precipitated procedures, the spontaneous opiate withdrawal paradigm used here revealed interesting gender- and morphine dose-linked differences. In particular, 56 h after last morphine administration elevated global opiate withdrawal scores were still evident in female but not in male mice treated with 20-100mg/kg. The severity of somatic opiate withdrawal directly correlated with the prior cumulative morphine exposure. Timing of expression of somatic opiate withdrawal signs also varied as a function of both gender and morphine dose. For example, expression of paw tremors and wet dog shakes was earlier in opiate-withdrawn male than in female mice. Overall, these findings highlight the possibility to detect gender- and opiate dose-linked differences in the expression and duration of somatic opiate withdrawal using a clinically relevant research model. The behavioral paradigm described here may represent a more appropriate tool to investigate the neurobiological bases of opiate withdrawal as opposed to opioid receptor antagonist-precipitated opiate withdrawal procedures
Decreased motivation to eat in mu-opioid receptor-deficient mice.
No full textAltered motivational processes might participate to the physiopathology of eating-related disorders. The endogenous opioid system is thought to mediate the hedonic properties of food intake. To assess the role for the micro-opioid receptor (MOR) pathway in the motivational properties of food intake, in the present study we tested wild-type and MOR-deficient mice (MOR-/-) in a nose-poke operant paradigm for chow or sucrose pellets. To avoid confounding factors linked to food restriction/deprivation experience, mice were always provided with food ad libitum. Although less MOR-/- than wild-type mice initiated operant behaviour, under a fixed ratio-1 (FR-1) reinforcement schedule the two genotypes showed similar patterns of food-driven nose-poking, indicating preserved cognitive abilities in MOR-deficient mice. However, during FR-3 and progressive ratio (PR) reinforcement experiments, MOR-/- mice showed lower levels of nose-poking for either chow or sucrose pellets than wild-type mice, indicating a crucial role for the MOR pathway in the motivational properties of food intake. Moreover, under the PR reinforcement schedule mice nose-poking for sucrose pellets showed higher genotype-independent breakpoint levels than mice working for chow pellets, indicating that the MOR pathway is not essential for hedonic processing of palatable food intake. Finally, MOR-/- mice did not differ from wild-type mice in the rate of operant responding extinction, further supporting the notion of unaltered cognitive abilities in the MOR-deficient mice. The present findings strongly indicate that the MOR pathway mediates the motivational properties of food intake, but it is not essential for hedonic processing of ingestive behaviour
Abecarnil enhances recovery from diazepam tolerance.
No full textTreatment with diazepam (25 mg/kg; p.o., twice-daily for 17 days) induced tolerance to the anticonvulsant effect of diazepam against bicuculline-induced convulsions in mice. Cross-tolerance was observed to the anticonvulsant action of clonazepam, imidazenil but not abecarnil. While substitution of clonazepam (12 mg/kg; p.o., twice-daily for 15 days) for diazepam did not affect tolerance to diazepam, substitution of imidazenil (17 mg/kg; p.o., twice-daily for 15 days) for diazepam significantly increased sensitivity to the anticonvulsant effect of diazepam, although tolerance was not abolished. Tolerance to diazepam progressively decreased either after suspension of diazepam administration or replacement treatment with abecarnil (20 mg/kg; p.o., twice-daily). Complete recovery of diazepam efficacy was detected after 8 and 15 days of administration of abecarnil and vehicle, respectively. Binding experiments using [H-3]-flumazenil showed that K-d values did not differ among treatment groups. A significant decrease in B-max (-42%) was observed in the cortex of diazepam-tolerant mice whether or not also treated with imidazenil and clonazepam. Conversely, chronically diazepam-treated mice, that further received abecarnil for either 8 or 15 days or vehicle for 15 days showed B-max values similar to those of vehicle-treated mice never exposed to diazepam. Results suggest that repeated abecarnil administration to diazepam-tolerant mice can facilitate re-adaptation of receptors to the diazepam-free state. It is proposed that replacement therapy with abecarnil after long-term treatment with conventional benzodiazepines (BDZs) may provide a novel approach for reducing tolerance to their anticonvulsant effects. (C) 1999 Elsevier Science Ltd. All rights reserved
Disruption of the CRF/CRF1 receptor stress system exacerbates the somatic signs of opiate withdrawal.
No full textEscape from the extremely stressful opiate withdrawal syndrome may motivate opiate seeking and taking. The corticotropin-releasing factor receptor-1 (CRF1) pathway mediates behavioral and endocrine responses to stress. Here, we report that genetic inactivation (CRF1-/-) as well as pharmacological antagonism of the CRF/CRF1 receptor pathway increased and prolonged the somatic expression of opiate withdrawal. Opiate-withdrawn CRF1-/- mice also showed aberrant CRF and dynorphin expression in the paraventricular nucleus of the hypothalamus (PVN) and the striatum, indicating profound impairments in stress-responsive brain circuitry. Intake of nonstressful amounts of corticosterone effectively reduced the exaggerated somatic reactions of CRF1-/- mice to opiate withdrawal. Exogenous corticosterone also restored "wild-type-like" patterns of CRF and dynorphin gene expression in the PVN and the striatum of opiate-withdrawn CRF1-/- mice, respectively. The present findings unravel a key role for the hypothalamus-pituitary-adrenal (HPA) system and brain extra-hypothalamic CRF/CRF1 receptor circuitry in somatic, molecular, and endocrine alterations induced by opiate withdrawal
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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