Quality of service at the computer networks based on internet

А framework for the emerging computer networks quality of Internet service is presented. Two important components of the framework are considered: integrated service and differentiated service. They are described and problems related to their implementation are discussed. Two broadly classified algorithms are investigated: scheduling and queue management algorithms. The model of the average time delay for the type packet is presented.Запропоновано структуру забезпечення якості надання послуг Internet. Розглянуто два важливі компоненти цієї структури: інтегроване та диференційоване обслуговування, їх реалізацію та пов’язані з нею проблеми. Досліджено два алгоритма: планування і управління чергою. Запропоновано модель даних, яка базується на теорії масового обслуговування.Предложена структура обеспечения качества предоставления услуг Internet. Рассмотрены два важных компонента этой структуры: интегрированное и дифференцированное обслуживание, их реализация и связанные с ней проблемы. Исследованы два алгоритма: планирования и управления очередью. Предложена модель данных, базирующаяся на теории массового обслуживания

Using conditioned suppression to investigate compulsive drug seeking in rats

Item does not contain fulltextBACKGROUND: Persistent drug seeking despite harmful consequences is a defining characteristic of addiction. Recent preclinical studies have demonstrated the occurrence of this hallmark feature of addictive behaviour in rodents. For example, it has been shown that the ability of an aversive conditioned stimulus (CS) to suppress cocaine seeking was diminished after an extended self-administration history. The present study aimed to optimize the experimental conditions to examine conditioned suppression of sucrose and cocaine seeking in rats, and its dependence on the longevity of self-administration experience. METHODS: We investigated whether conditioned suppression depends on the intensity and quantity of footshocks during conditioning. In addition, the effects of CS omission, extinction and reconditioning were investigated, as well as the influence of the CS interval sequence on conditioned suppression. We also compared conditioned suppression after a limited and extended sucrose or cocaine self-administration history. RESULTS: We found that conditioned suppression depended on the intensity rather than the quantity of footshocks, whereby a higher footshock intensity was necessary to induce suppression of cocaine seeking compared to sucrose seeking. Conditioned suppression was most pronounced when the test started with presentation of the aversive CS, and conditioned suppression could be extinguished and reacquired. In addition, conditioned suppression of cocaine, but not sucrose seeking was reduced after extended self-administration experience. CONCLUSIONS: These data provide a detailed analysis of conditioned suppression of cocaine and sucrose seeking. Importantly, we confirm the usefulness of conditioned suppression to study persistent drug seeking after prolonged drug self-administration

Stable immediate early gene expression patterns in medial prefrontal cortex and striatum after long-term cocaine self-administration.

The transition from casual to compulsive drug use is thought to occur as a consequence of repeated drug taking leading to neuroadaptive changes in brain circuitry involved in emotion and cognition. At the basis of such neuroadaptations lie changes in the expression of immediate early genes (IEGs) implicated in transcriptional regulation, synaptic plasticity and intracellular signalling. However, little is known about how IEG expression patterns change during long-term drug self-administration. The present study, therefore, compares the effects of 10 and 60-day self-administration of cocaine and sucrose on the expression of 17 IEGs in brain regions implicated in addictive behaviour, i.e. dorsal striatum, ventral striatum and medial prefrontal cortex (mPFC). Increased expression after cocaine self-administration was found for 6 IEGs in dorsal and ventral striatum (c-fos, Mkp1, Fosb/ΔFosb, Egr2, Egr4, and Arc) and 10 IEGs in mPFC (same 6 IEGs as in striatum, plus Bdnf, Homer1, Sgk1 and Rgs2). Five of these 10 IEGs (Egr2, Fosb/ΔFosb, Bdnf, Homer1 and Jun) and Trkb in mPFC were responsive to long-term sucrose self-administration. Importantly, no major differences were found between IEG expression patterns after 10 or 60days of cocaine self-administration, except Fosb/ΔFosb in dorsal striatum and Egr2 in mPFC, whereas the amount of cocaine obtained per session was comparable for short-term and long-term self-administration. These steady changes in IEG expression are, therefore, associated with stable self-administration behaviour rather than the total amount of cocaine consumed. Thus, sustained impulses to IEG regulation during prolonged cocaine self-administration may evoke neuroplastic changes underlying compulsive drug use

Social play behavior, ultrasonic vocalizations and their modulation by morphine and amphetamine in Wistar and Sprague-Dawley rats

RATIONALE: Social play behavior is the most characteristic social behavior in young mammals. It is highly rewarding and crucial for proper neurobehavioral development. Despite the importance of genetic factors in normal and pathological social behaviors, little information is available about strain influences on social play. OBJECTIVE AND METHODS: The aim of this study was to investigate differences in social play behavior, 50-kHz ultrasonic vocalizations (USVs) and their modulation by acute morphine and amphetamine administration in two rat strains widely used in behavioral pharmacology studies, i.e., Wistar and Sprague-Dawley rats. RESULTS: Sprague-Dawley rats showed higher levels of social play than Wistar rats. In both strains, no correlation was found between the performance of social behaviors and the emission of 50-kHz USVs. In Wistar and Sprague-Dawley rats, morphine increased and amphetamine decreased social play. The effects of morphine, however, were more pronounced in Wistar than Sprague-Dawley animals. In both strains, morphine did not affect USV emission, while amphetamine increased it during cage exploration. In Sprague-Dawley rats only, amphetamine decreased USVs during social interaction. CONCLUSIONS: Wistar and Sprague-Dawley rats differ in their absolute levels of social play behavior and 50-kHz USVs, and quantitative differences exist in their response to pharmacological manipulations of social play. The emission of 50-kHz USVs and the behavioral parameters thought to reflect rewarding social interactions in adolescent rats are dissociable