The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform
William J. Mcbride - One of the best experts on this subject based on the ideXlab platform.
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Intracranial Self-Administration of Cocaine within the Posterior Ventral Tegmental Area of Wistar Rats: Evidence for Involvement of Serotonin-3 Receptors and Dopamine Neurons
Journal of Pharmacology and Experimental Therapeutics, 2005Co-Authors: Zachary A. Rodd, Richard L. Bell, Ying Zhang, James M. Murphy, William J. McbrideAbstract:The rewarding properties of cocaine have been postulated to be regulated, in part, by the mesolimbic dopamine (DA) system. The present study assessed whether adult female Wistar rats would self-administer cocaine directly into the ventral tegmental area (VTA). Following guide cannulae surgery aimed at either the posterior or anterior VTA, subjects were placed in an operant box equipped with an active lever that caused the delivery of the infusate and an inactive lever that did not. Posterior and anterior VTA subjects were randomly assigned to one of six groups that self-administered either artificial cerebrospinal fluid (aCSF) or 25 to 400 pmol cocaine/100 nl in aCSF for the first four sessions, aCSF in sessions 5 and 6, and the acquisition dose of infusate during session 7. Additionally, the effects of increasing the Time-Out Period, higher concentrations of cocaine, coadministration of a 5HT 3 antagonist, and coadministration of a D 2/3 agonist on self-infusion of cocaine were determined. Self-infusions were maintained when the Time-Out Period was extended from 5 to 25 s. Coinfusion of a 5HT 3 antagonist or D 2/3 agonist blocked the self-infusion of cocaine. In contrast, rats did not self-administer 25 to 400 pmol/100 nl cocaine into the anterior VTA. Additionally, rats did not self-administer either 800 or 1600 pmol/100 nl cocaine into the posterior or anterior VTA. Overall, the data indicate that the VTA is functionally heterogeneous with regard to the rewarding actions of cocaine and that the reinforcing effects of cocaine within the posterior VTA are mediated by activation 5-HT 3 receptors and DA neurons.
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The reinforcing effects of acetaldehyde in the posterior ventral tegmental area of alcohol-preferring rats.
Pharmacology Biochemistry and Behavior, 2002Co-Authors: Zachary A. Rodd-henricks, Roberto I. Melendez, Alejandro Zaffaroni, Avram Goldstein, William J. McbrideAbstract:Acetaldehyde (ACD), the first metabolite of ethanol, is a biologically active compound, which may mediate some of the reinforcing, behavioral and neurotoxic effects of ethanol. The objective of this study was to test the hypothesis that ACD is reinforcing within the mesolimbic system. The intracranial self-administration (ICSA) technique was employed to determine whether ACD was reinforcing in the posterior ventral tegmental area (VTA), a site that supports the reinforcing actions of ethanol. Adult female alcohol-preferring (P) rats were implanted with guide cannulae aimed at the posterior VTA. Subjects were placed in two-lever operant chambers 7-10 days after surgery. Responding on the "active lever" on a fixed ratio 1 (FR1) schedule of reinforcement caused the delivery of 100 nl of infusate, whereas responses on the "inactive lever" were without consequences. Rats were assigned to one of five groups that self-administered either artificial cerebrospinal fluid (aCSF) throughout all eight sessions (4 h in duration) or 3- and 6-, 11- and 23-, 45- and 90- or 180- and 360-microM ACD for the eight sessions, with the lower concentration of ACD given for the initial four sessions and the higher concentration of ACD given for the last four sessions. A second experiment examined the acquisition (first four sessions), extinction (aCSF in sessions 5 and 6) and reinstatement using 90-microM ACD. A third experiment examined the effects of extending the Time-Out Period (from 5 to 55 s) on the number and pattern of infusions of 23-microM ACD. Adult P rats readily self-administered 6-90-microM ACD and discriminated between the active and inactive levers. Furthermore, rats self-administering 90-microM ACD also demonstrated extinction behavior when aCSF was substituted for ACD and gradually reinstated active lever responding when ACD was reintroduced. P rats maintained similar numbers of infusions and infusion patterns under both Time-Out schedules. Overall, the data indicate that ACD is a potent reinforcer within the posterior VTA of the P rat.
Carlos M P Sousa - One of the best experts on this subject based on the ideXlab platform.
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export market re entry time out Period and price quality dynamisms
Journal of World Business, 2019Co-Authors: Jieke Chen, Carlos M P SousaAbstract:The relevance of nonlinear internationalisation regarding exporting activities and the performance post re-entry remains little understood. This study develops a two-stage model to explain the process of exporting firms’ exit and re-entry decisions regarding individual export markets. Specifically, it investigates the dynamic relationships between exit and re-entry stages by focusing on the Time-Out Period. This study empirically tests the decision model by employing export data from the Chinese Customs for the Period 2000-2009. The results indicate the importance of the exit stage in shaping re-entry decisions, price/quality ratio and export performance, where Time-Out Period plays a significant role in varying these effects.
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Export market re-entry: Time-Out Period and price/quality dynamisms
Journal of World Business, 2019Co-Authors: Jieke Chen, Carlos M P SousaAbstract:Abstract The relevance of nonlinear internationalisation regarding exporting activities and the performance post re-entry remains little understood. This study develops a two-stage model to explain the process of exporting firms’ exit and re-entry decisions regarding individual export markets. Specifically, it investigates the dynamic relationships between exit and re-entry stages by focusing on the Time-Out Period. This study empirically tests the decision model by employing export data from the Chinese Customs for the Period 2000-2009. The results indicate the importance of the exit stage in shaping re-entry decisions, price/quality ratio and export performance, where Time-Out Period plays a significant role in varying these effects.
Patrick M. Beardsley - One of the best experts on this subject based on the ideXlab platform.
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Dose history and occurrence of conditional stimuli determine the strength of cocaine-seeking behavior of rhesus monkeys
International Journal of Comparative Psychology, 2005Co-Authors: Jennifer L. Newman, Patrick M. BeardsleyAbstract:Four adult male rhesus monkeys were trained to lever press for cocaine under a daily two-component MIX PR (progressive ratio) schedule. During the first 10 min of experimental sessions, completion of progressive ratios resulted in 1-s presentations of brief visual stimuli (BS; colored lights) associated with cocaine infusions during the second component. Stimulus lights of different colors were associated with doses of 3, 30, and 300 μg/kg cocaine as the available self-administered infusate. A 5-min time out Period followed the first component, which in turn was followed by a 60-min component during which completion of progressive ratios resulted in cocaine infusions and the associated visual stimuli. Once reinforcer rates had stabilized under each dosing condition in both components, break point tests were conducted separately for BS as the reinforcer and with cocaine + stimuli as the reinforcer. Break points for lever pressing maintained by BS alone increased as they were paired with increasing doses of cocaine. Break points maintained by actual cocaine delivery, however, demonstrated an inverted U-shaped function to cocaine dose. The results of this study suggest that the strength of cocaine-seeking behavior varies monotonically with the self-administered dose of cocaine and that the level of motivation to obtain cocaine may not be directly revealed by levels of actual cocaine self-administration.
Jane Stewart - One of the best experts on this subject based on the ideXlab platform.
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A role for the prefrontal cortex in stress- and cocaine-induced reinstatement of cocaine seeking in rats.
Psychopharmacology, 2002Co-Authors: Nancy Capriles, Demetra Rodaros, Robert E Sorge, Jane StewartAbstract:It is well established that stress induces reinstatement of drug seeking in an animal model of relapse. Here we studied the role of the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) in foot-shock stress-induced reinstatement of cocaine seeking. Groups of rats were trained to self-administer cocaine (0.5 mg/kg per infusion, i.v., 3 h/day for 9 days) and after ten drug-free days were exposed to extinction and reinstatement test sessions. Each 60 min of extinction was separated by a 30-min Time-Out Period after which the lever and stimulus lights were reintroduced. Rats were given four 1-h extinction sessions on day 1 and then on subsequent days were given two to three 1-h extinction sessions that were followed by a 3-h test for reinstatement. Tests were run every 48 h. In one set of experiments, the effects of inactivation of the prelimbic (PL), infralimbic (IL) or OFC by tetrodotoxin (TTX, 5 ng/0.5 micro l per side) on reinstatement induced by foot shock (5 min, intermittent, 1 mA) or priming injections of cocaine (20 mg/kg, i.p.) were determined. In a second set, the effects of infusions of the D1-like and D2-like dopamine receptor antagonists (SCH 23390 and raclopride) were studied using the same methods. TTX infusions into the PL cortex blocked both foot shock and cocaine-induced reinstatement. TTX into OFC attenuated foot-shock-induced, but not cocaine-induced reinstatement. Infusions into IL were ineffective. Infusions of SCH 22390 (0.25 micro g/0.5 micro l per side) into either PL or OFC blocked foot-shock-induced reinstatement, but infusions into PL had no effect on cocaine-induced reinstatement. Raclopride (5 micro g/0.5 micro l per side) had no effect on foot-shock-induced reinstatement in either PL or OFC or on cocaine-induced reinstatement when infused into PL. Neither TTX nor SCH23390 infusions into PL or OFC had any effect on lever pressing for sucrose. These results suggest that the PL and OFC regions form part of the circuitry mediating the effects of foot shock stress on reinstatement of drug seeking and that the PL region may be a common pathway for cue, drug and foot-shock stress-induced reinstatement of drug seeking.
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A role for the prefrontal cortex in stress- and cocaine-induced reinstatement of cocaine seeking in rats
Psychopharmacology, 2002Co-Authors: Nancy Capriles, Demetra Rodaros, Robert E Sorge, Jane StewartAbstract:Rationale and objective It is well established that stress induces reinstatement of drug seeking in an animal model of relapse. Here we studied the role of the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) in foot-shock stress-induced reinstatement of cocaine seeking. Methods: Groups of rats were trained to selfadminister cocaine (0.5 mg/kg per infusion, i.v., 3 h/day for 9 days) and after ten drug-free days were exposed to extinction and reinstatement test sessions. Each 60 min of extinction was separated by a 30-min Time-Out Period after which the lever and stimulus lights were reintroduced. Rats were given four 1-h extinction sessions on day 1 and then on subsequent days were given two to three 1-h extinction sessions that were followed by a 3-h test for reinstatement. Tests were run every 48 h. In one set of experiments, the effects of inactivation of the prelimbic (PL), infralimbic (IL) or OFC by tetrodotoxin (TTX, 5 ng/0.5 �l per side) on reinstatement induced by foot shock (5 min, intermittent, 1 mA) or priming injections of cocaine (20 mg/kg, i.p.) were determined. In a second set, the effects of infusions of the D1-like and D2-like dopamine receptor antagonists (SCH 23390 and raclopride) were studied using the same methods. Results: TTX infusions into the PL cortex blocked both foot shock and cocaine-induced reinstatement. TTX into OFC attenuated foot-shock-induced, but not cocaine-induced reinstatement. Infusions into IL were ineffective. Infusions of SCH 22390 (0.25 �g/0.5 �l per side) into either PL or OFC blocked foot-shock-induced reinstatement, but infusions into PL had no effect on cocaine-induced reinstatement. Raclopride (5 �g/0.5 �l per side) had no effect on foot-shock-induced reinstatement in either PL or OFC or on cocaine-induced reinstatement when infused into PL. Neither TTX nor SCH23390 infusions into PL or OFC had any effect on lever pressing for sucrose. Conclusions: These results suggest that the PL and OFC regions form part of the circuitry mediating the effects of foot shock stress on reinstatement of drug seeking and that the PL region may be a common pathway for cue, drug and foot-shock stress-induced reinstatement of drug seeking.
Jieke Chen - One of the best experts on this subject based on the ideXlab platform.
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export market re entry time out Period and price quality dynamisms
Journal of World Business, 2019Co-Authors: Jieke Chen, Carlos M P SousaAbstract:The relevance of nonlinear internationalisation regarding exporting activities and the performance post re-entry remains little understood. This study develops a two-stage model to explain the process of exporting firms’ exit and re-entry decisions regarding individual export markets. Specifically, it investigates the dynamic relationships between exit and re-entry stages by focusing on the Time-Out Period. This study empirically tests the decision model by employing export data from the Chinese Customs for the Period 2000-2009. The results indicate the importance of the exit stage in shaping re-entry decisions, price/quality ratio and export performance, where Time-Out Period plays a significant role in varying these effects.
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Export market re-entry: Time-Out Period and price/quality dynamisms
Journal of World Business, 2019Co-Authors: Jieke Chen, Carlos M P SousaAbstract:Abstract The relevance of nonlinear internationalisation regarding exporting activities and the performance post re-entry remains little understood. This study develops a two-stage model to explain the process of exporting firms’ exit and re-entry decisions regarding individual export markets. Specifically, it investigates the dynamic relationships between exit and re-entry stages by focusing on the Time-Out Period. This study empirically tests the decision model by employing export data from the Chinese Customs for the Period 2000-2009. The results indicate the importance of the exit stage in shaping re-entry decisions, price/quality ratio and export performance, where Time-Out Period plays a significant role in varying these effects.
