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Kallupi M, Scuppa G, de Guglielmo G, Calò G, Weiss F, Statnick MA, Rorick-Kehn LM, Ciccocioppo R. Genetic Deletion of the Nociceptin/Orphanin FQ Receptor in the Rat Confers Resilience to the Development of Drug Addiction. Neuropsychopharmacology 2017; 42:695-706. [PMID: 27562376 PMCID: PMC5240182 DOI: 10.1038/npp.2016.171] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 08/12/2016] [Accepted: 08/13/2016] [Indexed: 12/14/2022]
Abstract
The nociceptin (NOP) receptor is a G-protein-coupled receptor whose natural ligand is the NOP/orphanin FQ (N/OFQ) peptide. Evidence from pharmacological studies suggests that the N/OFQ system is implicated in the regulation of several addiction-related phenomena, such as drug intake, withdrawal, and relapse. Here, to further explore the role of NOP system in addiction, we used NOP (-/-) rats to study the motivation for cocaine, heroin, and alcohol self-administration in the absence of N/OFQ function. Conditioned place preference (CPP) and saccharin (0.2% w/v) self-administration were also investigated. Results showed that NOP (-/-) rats self-administer less cocaine (0.25, 0.125, or 0.5 mg/infusion) both under a fixed ratio 1 and a progressive ratio schedule of reinforcement compared with wild-type (Wt) controls. Consistently, cocaine (10 mg/kg, i.p.) was able to induce CPP in Wt but not in NOP (-/-). When NOP (-/-) rats were tested for heroin (20 μg/infusion) and ethanol (10% v/v) self-administration, they showed significantly lower drug intake compared with Wt. Conversely, saccharin self-administration was not affected by NOP deletion, excluding the possibility of nonspecific learning deficits or generalized disruption of reward mechanisms in NOP (-/-) rats. These findings were confirmed with pharmacological experiments using two selective NOP antagonists, SB-612111 and LY2817412. Both drugs attenuated alcohol self-administration in Wt rats but not in NOP (-/-) rats. In conclusion, our results demonstrate that genetic deletion of NOP receptors confers resilience to drug abuse and support a role for NOP receptor antagonism as a potential treatment option for drug addiction.
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Affiliation(s)
- Marsida Kallupi
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy,Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
| | - Giulia Scuppa
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Giordano de Guglielmo
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy,Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
| | - Girolamo Calò
- Department of Medical Science, Section of Pharmacology and National Institute of Neuroscience, University of Ferrara, Ferrara, Italy
| | - Friedbert Weiss
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute, La Jolla, CA, USA
| | - Michael A Statnick
- Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN USA
| | | | - Roberto Ciccocioppo
- School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, Italy,School of Pharmacy, Pharmacology Unit, University of Camerino, Camerino, 62032 Italy, Tel: +39 07 3740 3313, Fax: +39 07 3740 3325, E-mail:
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Filip M, Frankowska M, Jastrzębska J, Wydra K, Przegaliński E. Preclinical studies on comorbidity between depression and psychostimulant addiction. Pharmacol Rep 2013; 65:1529-34. [DOI: 10.1016/s1734-1140(13)71514-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 10/08/2013] [Indexed: 12/14/2022]
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Kest K, Cruz I, Chen DH, Galaj E, Ranaldi R. A food-associated CS activates c-Fos in VTA DA neurons and elicits conditioned approach. Behav Brain Res 2012; 235:150-7. [PMID: 22963991 DOI: 10.1016/j.bbr.2012.07.044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 07/27/2012] [Accepted: 07/31/2012] [Indexed: 11/29/2022]
Abstract
Neutral stimuli associated with unconditioned stimuli (USs) acquire the ability to act as conditioned stimuli (CSs), which can elicit behaviors similar to the US with which they are associated. The neural mechanisms by which this occurs are not fully known. We have previously proposed a model stipulating CSs function as such because they acquire the capacity to activate dopamine (DA) neurons at the level of the ventral tegmental area (VTA). In the present experiments we hypothesized that a food-associated CS (light), which demonstrably functions as such by eliciting conditioned responses (CRs), comes to acquire the capacity to activate VTA DA neurons. In Experiment 1, rats were allowed to eat or not eat food (food being the US). In Experiment 2, rats were trained to retrieve food pellets after light presentations (the CS) and then tested for the expression of the food checking response (the CR) with only CS presentations. In Experiment 1, eating food (exposure to the US) caused a significantly greater number of VTA DA (TH-labeled) cells to express c-Fos than not eating. In Experiment 2, CS (light) presentations caused a significant amount of conditioned approach and a significantly greater number of VTA TH-labeled (DA) cells to express c-Fos. These findings support our model stipulating that conditioned approach learning occurs when CSs acquire the capacity to cause conditioned activation of VTA DA neurons.
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Affiliation(s)
- Karen Kest
- Graduate Center, City University of New York, United States
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Edwards S, Bachtell RK, Guzman D, Whisler KN, Self DW. Emergence of context-associated GluR(1) and ERK phosphorylation in the nucleus accumbens core during withdrawal from cocaine self-administration. Addict Biol 2011; 16:450-7. [PMID: 21309958 DOI: 10.1111/j.1369-1600.2010.00296.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reexposure to cocaine-associated environments promotes relapse to cocaine seeking and represents a persistent impediment to successful abstinence. Neurobiological adaptations are thought to underlie the preservation of drug-seeking behavior during protracted withdrawal periods, possibly including changes associated specifically with cocaine-paired contexts. We measured GluR(1) (S845) and extracellular signal-regulated kinase (ERK) phosphorylation in rat striatal subregions in an animal model of cocaine relapse. Animals with cocaine self-administration experience and their yoked partners were exposed to extinction conditions for one hour in the drug-paired environmental context after one day or three weeks withdrawal to measure protein phosphorylation induced by the cocaine-paired context in the absence of cocaine reinforcement. GluR(1) (S845) (an index of protein kinase A (PKA) activity) and ERK phosphorylation increased in the nucleus accumbens core of self-administering but not yoked animals after three weeks (but not one day) withdrawal, indicating a time-dependent emergence of context-associated protein phosphorylation in this accumbens subregion. In comparison, animals trained to self-administer sucrose displayed a similar increase in ERK, but not GluR(1) (S845) , phosphorylation following reexposure to a sucrose-paired environment three weeks later, indicating that GluR(1) (S845) phosphorylation did not result solely from lever press behavior per se. In contrast, basal (home cage) GluR(1) (S845) phosphorylation was elevated in the nucleus accumbens shell and caudate-putamen after one day or three weeks cocaine withdrawal regardless of context exposure. These results suggest that time-dependent emergence of context-associated GluR(1) (S845) phosphorylation in the nucleus accumbens core may contribute to the persistence of cocaine-seeking behavior, whereas ERK phosphorylation may be a consequence of this behavior.
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Affiliation(s)
- Scott Edwards
- Department of Psychiatry and Neuroscience Graduate Program, The Seay Center for Basic and Applied Research in Psychiatric Illness, UT Southwestern Medical Center, Dallas, TX 75390-9070, USA
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Dhanya RP, Sidique S, Sheffler DJ, Nickols HH, Herath A, Yang L, Dahl R, Ardecky R, Semenova S, Markou A, Conn PJ, Cosford NDP. Design and synthesis of an orally active metabotropic glutamate receptor subtype-2 (mGluR2) positive allosteric modulator (PAM) that decreases cocaine self-administration in rats. J Med Chem 2010; 54:342-53. [PMID: 21155570 DOI: 10.1021/jm1012165] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The modification of 3'-((2-cyclopentyl-6,7-dimethyl-1-oxo-2,3-dihydro-1H-inden-5-yloxy)methyl)biphenyl-4-carboxylic acid (BINA, 1) by incorporating heteroatoms into the structure and replacing the cyclopentyl moiety led to the development of new mGluR2 positive allosteric modulators (PAMs) with optimized potency and superior druglike properties. These analogues are more potent than 1 in vitro and are highly selective for mGluR2 vs other mGluR subtypes. They have significantly improved pharmacokinetic (PK) properties, with excellent oral bioavailability and brain penetration. The benzisothiazol-3-one derivative 14 decreased cocaine self-administration in rats, providing proof-of-concept for the use of mGluR2 PAMs for the treatment of cocaine dependence.
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Affiliation(s)
- Raveendra-Panickar Dhanya
- Conrad Prebys Center for Chemical Genomics, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, United States
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Jin X, Semenova S, Yang L, Ardecky R, Sheffler DJ, Dahl R, Conn PJ, Cosford NDP, Markou A. The mGluR2 positive allosteric modulator BINA decreases cocaine self-administration and cue-induced cocaine-seeking and counteracts cocaine-induced enhancement of brain reward function in rats. Neuropsychopharmacology 2010; 35:2021-36. [PMID: 20555310 PMCID: PMC2922422 DOI: 10.1038/npp.2010.82] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Metabotropic glutamate receptor 2/3 (mGluR2/3) agonists were shown previously to nonselectively decrease both cocaine- and food-maintained responding in rats. mGluR2 positive allosteric modulators (PAMs) may represent improved therapeutic compounds because of their modulatory properties and higher selectivity for mGluR2. We analyzed the effects of the selective, brain penetrant, and systemically active mGluR2 PAM potassium 3'-([(2-cyclopentyl-6-7-dimethyl-1-oxo-2,3-dihydro-1H-inden-5-yl)oxy]methyl)biphenyl l-4-carboxylate (BINA) and the mGluR2/3 agonist LY379268 on intravenous cocaine self-administration and cocaine-seeking behavior in rats that had short (1 h, ShA) or long (6 h, LgA) access to cocaine. The effects of BINA on food responding and food-seeking behavior were also analyzed. Finally, we examined the effects of BINA on brain reward function and cocaine-induced reward enhancement using the intracranial self-stimulation procedure. BINA decreased cocaine self-administration in both ShA and LgA rats, with no effect on food self-administration. Alternatively, LY379268 nonselectively decreased both cocaine and food self-administration. BINA decreased cue-induced reinstatement of cocaine seeking with no effect on food seeking. The cocaine-induced enhancement of brain reward function was blocked by BINA, although the highest doses of BINA decreased brain reward function when administered alone, suggesting additive, rather than interactive, effects of BINA and cocaine. In conclusion, BINA attenuated the reinforcing and counteracted the reward-enhancing effects of cocaine and decreased cue-induced cocaine-seeking behavior, without affecting behaviors motivated by food reinforcement. The higher selectivity of BINA compared with an mGluR2/3 agonist for drug- vs food-motivated behaviors suggests a therapeutic role for mGluR2 PAMs for the treatment of cocaine addiction and possibly other drugs of abuse.
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Affiliation(s)
- Xinchun Jin
- Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Svetlana Semenova
- Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Li Yang
- Program on Apoptosis and Cell Death, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA
| | - Robert Ardecky
- Program on Apoptosis and Cell Death, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA
| | - Douglas J Sheffler
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Russell Dahl
- Program on Apoptosis and Cell Death, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA
| | - P Jeffrey Conn
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Nicholas DP Cosford
- Program on Apoptosis and Cell Death, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA
| | - Athina Markou
- Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla, CA, USA,Department of Psychiatry, M/C 0603, School of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0603, USA, Tel: +1 858 534 1572, Fax: +1 858 534 9917, E-mail:
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Hyman SE, Malenka RC, Nestler EJ. Neural mechanisms of addiction: the role of reward-related learning and memory. Annu Rev Neurosci 2006; 29:565-98. [PMID: 16776597 DOI: 10.1146/annurev.neuro.29.051605.113009] [Citation(s) in RCA: 1784] [Impact Index Per Article: 99.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Addiction is a state of compulsive drug use; despite treatment and other attempts to control drug taking, addiction tends to persist. Clinical and laboratory observations have converged on the hypothesis that addiction represents the pathological usurpation of neural processes that normally serve reward-related learning. The major substrates of persistent compulsive drug use are hypothesized to be molecular and cellular mechanisms that underlie long-term associative memories in several forebrain circuits (involving the ventral and dorsal striatum and prefrontal cortex) that receive input from midbrain dopamine neurons. Here we review progress in identifying candidate mechanisms of addiction.
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Affiliation(s)
- Steven E Hyman
- Office of the Provost, Harvard University, Cambridge, Massachusetts 02138, USA.
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Bespalov AY, Dravolina OA, Sukhanov I, Zakharova E, Blokhina E, Zvartau E, Danysz W, van Heeke G, Markou A. Metabotropic glutamate receptor (mGluR5) antagonist MPEP attenuated cue- and schedule-induced reinstatement of nicotine self-administration behavior in rats. Neuropharmacology 2005; 49 Suppl 1:167-78. [PMID: 16023685 DOI: 10.1016/j.neuropharm.2005.06.007] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 06/06/2005] [Accepted: 06/09/2005] [Indexed: 11/22/2022]
Abstract
Previous studies suggested that metabotropic glutamate 5 (mGlu5) receptors play an important role in the reinforcing effects of abused drugs. The present experiments evaluated the effects of the mGlu5 receptor antagonist, MPEP (2-methyl-6-(phenylethynyl)-pyridine hydrochloride; 1-10 mg/kg, salt, i.p.), in rat models of nicotine-seeking behavior that may have relevance to relapse to drug-taking. Male Wistar rats (with restricted access to food) were trained to nose-poke to receive intravenous infusions of nicotine (0.03 mg/kg per infusion, base) under a fixed ratio 5 time out 60 s schedule of reinforcement. After stable nicotine self-administration was acquired, nose-poking behavior was extinguished in the absence of nicotine-associated cues. During the reinstatement test phase, independent groups of animals were exposed to: (a) response-contingent nicotine-associated cues (cue-induced reinstatement); or (b) response-noncontingent presentations of 45-mg food pellets under fixed time 2 min schedule (schedule-induced reinstatement). Additional control experiments were conducted to demonstrate that in nicotine-naïve animals MPEP does not affect cue-induced reinstatement of food-seeking behavior and has no effects on operant behavior maintained by a simple fixed interval 2 min schedule of food reinforcement. Pretreatment with MPEP (10 mg/kg) significantly attenuated the reinstatement of nicotine-seeking in both experiments. Further, MPEP (10 mg/kg) significantly attenuated polydipsia induced by a fixed time 2 min food schedule. In conclusion, the present findings indicate that the blockade of mGlu5 receptors attenuates cue-induced reinstatement of nicotine self-administration behavior (but not food-seeking) and may produce a general inhibition of schedule-induced behaviors, including schedule-induced nicotine-seeking.
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Affiliation(s)
- Anton Y Bespalov
- Institute of Pharmacology, Pavlov Medical University, St. Petersburg, Russia.
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Carroll ME, Batulis DK, Landry KL, Morgan AD. Sex differences in the escalation of oral phencyclidine (PCP) self-administration under FR and PR schedules in rhesus monkeys. Psychopharmacology (Berl) 2005; 180:414-26. [PMID: 15739077 DOI: 10.1007/s00213-005-2182-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Accepted: 01/06/2005] [Indexed: 01/18/2023]
Abstract
RATIONALE Studies with male rats indicate that long access (LgA) vs short access (ShA) to i.v. cocaine and heroin self-administration leads to an escalation of drug intake and a subsequent upward shift of the dose-response function. OBJECTIVE The purpose of this experiment was to extend these results to male and female rhesus monkeys and oral phencyclidine (PCP) self-administration under fixed-ratio (FR) and progressive-ratio (PR) schedules. METHODS Adult rhesus monkeys (seven females and nine males) orally self-administered PCP (0.25 mg/ml) and water under concurrent FR 16 FR 16 schedules during daily ShA 3-h sessions. Since females weighed less than males, each liquid delivery (0.6 ml) represented a higher unit dose mg/kg for females than males, but drug concentration mg/ml remained constant. Concurrent PR PR schedules were then used to obtain a concentration-response function (0.125, 0.25, 0.5, and 1.0 mg/ml). Next, PCP and water were available during LgA 6-h sessions under concurrent FR 16 FR 16 schedules for 21 days. The monkeys were then retested under the concurrent FR 16 FR 16 and PR PR conditions during ShA sessions. RESULTS Under the initial ShA concurrent FR 16 FR 16 schedules, females and males did not differ on PCP deliveries or intake (mg/kg); however, during LgA, males and females had more PCP deliveries compared with ShA. During LgA, males exceeded females in PCP deliveries, but females were higher than males in mg/kg PCP intake. Also, PCP (but not water) deliveries and mg/kg PCP intake significantly increased from the first 3 days to the last 3 days of the 21-day LgA period in both males and females. The subsequent ShA FR 16 FR 16 performance did not differ by sex, but it was significantly elevated above the first ShA period in both sexes. The concentration-response function for PCP break point under the PR PR schedules and PCP intake (mg/kg) were significantly shifted upward during the second (vs first) ShA period, and females' mg/kg intake significantly exceeded males'. CONCLUSIONS Male and female rhesus monkeys both showed escalation of PCP self-administration during LgA to PCP and during ShA that occurred after (vs before) LgA. Both showed vertical upward shifts in the concentration x intake (mg/kg) function under the PR schedule, and females exceeded males on this measure. These findings with PCP and monkeys are consistent with vertical upward shifts of cocaine dose-response functions in previous escalation studies in male rats and reports of sex differences (F>M) during several other phases of drug abuse.
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Affiliation(s)
- Marilyn E Carroll
- Department of Psychiatry, University of Minnesota, MMC 392, Minneapolis, MN 55455, USA.
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Barr AM, Markou A. Psychostimulant withdrawal as an inducing condition in animal models of depression. Neurosci Biobehav Rev 2005; 29:675-706. [PMID: 15893821 DOI: 10.1016/j.neubiorev.2005.03.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A large body of evidence indicates that the withdrawal from high doses of psychostimulant drugs in humans induces a transient syndrome, with symptoms that appear isomorphic to those of major depressive disorder. Pharmacological treatment strategies for psychostimulant withdrawal in humans have focused mainly on compounds with antidepressant properties. Animal models of psychostimulant withdrawal have been shown to demonstrate a wide range of deficits, including changes in homeostatic, affective and cognitive behaviors, as well as numerous physiological changes. Many of these behavioral and physiological sequelae parallel specific symptoms of major depressive disorder, and have been reversed by treatment with antidepressant drugs. These combined findings provide strong support for the use of psychostimulant withdrawal as an inducing condition in animal models of depression. In the current review we propound that the psychostimulant withdrawal model displays high levels of predictive and construct validity. Recent progress and limitations in the development of this model, as well as future directions for research, are evaluated and discussed.
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Affiliation(s)
- Alasdair M Barr
- Department of Neuropharmacology, CVN-7, The Scripps Research Institute, 10550 North Torrey Pines Rd, La Jolla, CA 92037 USA
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Lu L, Grimm JW, Dempsey J, Shaham Y. Cocaine seeking over extended withdrawal periods in rats: different time courses of responding induced by cocaine cues versus cocaine priming over the first 6 months. Psychopharmacology (Berl) 2004; 176:101-8. [PMID: 15071719 DOI: 10.1007/s00213-004-1860-4] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2004] [Accepted: 02/29/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE AND OBJECTIVES We previously found time dependent increases, or incubation, of cocaine seeking induced by re-exposure to cocaine cues over withdrawal periods of up to 3 months. Here, we studied cocaine seeking induced by re-exposure to cocaine cues or cocaine itself over an extended withdrawal period of 6 months. METHODS Rats were trained to self-administer intravenous cocaine for 6 h/day for 10 days. Cocaine seeking induced by re-exposure to cocaine cues or cocaine itself, as measured in extinction or drug-induced reinstatement tests, respectively, was then assessed 1 day, or 1, 3 or 6 months after withdrawal. Rats were first given six 1-h extinction sessions wherein lever presses resulted in contingent presentations of cues previously paired with cocaine infusions. Subsequently, reinstatement of drug seeking induced by cocaine injections (expt 1: 0, 5, and 15 mg/kg, i.p.; expt 2: 0, 2.5, and 5 mg/kg) was assessed during three 1-h sessions. RESULTS Profound time dependent changes in responsiveness to cocaine cues in the extinction tests were observed, with low responding after 1 day, high responding after 1 and 3 months, and intermediate responding after 6 months of withdrawal. In contrast, no significant time dependent changes in cocaine-induced drug seeking were found; acute re-exposure to cocaine effectively reinstated responding at all withdrawal periods. CONCLUSIONS Results indicate that the withdrawal period is a critical modulator of drug seeking provoked by re-exposure to cocaine cues, but not cocaine itself. Results also indicate that while the incubation of responsiveness to cocaine cues is a long lasting phenomenon, it is not permanent.
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Affiliation(s)
- Lin Lu
- Behavioral Neuroscience Branch, IRP/NIDA/NIH/DHHS, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA
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Wilson DIG, Bowman EM. Second-order stimuli do not always increase overall response rates in second-order schedules of reinforcement in the rat. Psychopharmacology (Berl) 2004; 174:430-7. [PMID: 15083254 DOI: 10.1007/s00213-004-1867-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Accepted: 03/02/2004] [Indexed: 10/26/2022]
Abstract
RATIONALE Second-order schedules of reinforcement have been used extensively to model reward-seeking and drug-seeking behaviour. Second-order stimuli within second-order schedules have been shown to enhance response rates during operant responding for natural reinforcers and drug reinforcers. This has led some to view second-order schedules of drug reinforcement as a model maintained of drug-seeking in addicts by drug-associated stimuli. However, the functional role of the second-order stimulus within second-order schedules is complex. OBJECTIVE We investigated the role of second-order stimuli within a second-order schedule of reinforcement [FI 4 min (FR10: S)] maintained by sweetened water reinforcement. METHODS Eight rats were trained to press a bar on a second-order schedule of reinforcement and tested in the presence and absence of the second-order stimulus. RESULTS In contrast to most previous work, overall bar-pressing rates were significantly increased when the second-order stimulus was omitted (second-order stimulus omission: 0.17 Hz (+/-0.04, 95% CI); second-order stimulus present: 0.13 Hz (+/-0.04, 95% CI)). However, second-order stimuli also changed the pattern of responding whereby rats would make a bout of bar presses prior to the presentation of the second-order stimulus and then pause briefly after the second-order stimulus. In the absence of second-order stimuli, responding was uniformly high. Control measures, such as the ability of the second-order stimulus to evoke checking for the primary reinforcers, indicated that the second-order stimulus was associated with the primary reinforcer. CONCLUSIONS These results demonstrated that although second-order stimuli maintained responding and caused the rat to check for primary reinforcement, overall response rates were increased when the second-order stimuli were omitted. This has implications for interpreting the results of studies where overall response rates within second-order schedules have been the only measure used to assess the effects of potential anti-addiction drugs. Future studies could be improved by performing a second-order stimulus omission test analysing both the overall response rates and the temporal organization of responding with respect to the second-order stimulus.
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Affiliation(s)
- David I G Wilson
- School of Psychology, St Mary's College, University of St Andrews, South Street, St Andrews, Fife KY16 9JP, UK.
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Kenny PJ, Koob GF, Markou A. Conditioned facilitation of brain reward function after repeated cocaine administration. Behav Neurosci 2004; 117:1103-7. [PMID: 14570559 DOI: 10.1037/0735-7044.117.5.1103] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cocaine lowers brain reward thresholds, reflecting increased brain reward function. The authors investigated whether, similar to acute cocaine administration, cocaine-predictive conditioned stimuli would lower intracranial self-stimulation (ICSS) thresholds. Rats received a saline injection for 5 days, a cocaine injection (10 mg/kg) for 20 consecutive days, then saline for 5 additional days. Thresholds were measured immediately before and 10 min after each injection. The initial 5 saline injections had no effect on thresholds, whereas cocaine significantly lowered thresholds for 20 days. There was no tolerance or sensitization to this effect of cocaine over days. During the last 5 days when cocaine administration was substituted with saline, rats demonstrated a conditioned lowering of thresholds during the 2nd daily ICSS session. These data demonstrate that cocaine-predictive conditioned stimuli induce a conditioned facilitation of brain reward function.
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Affiliation(s)
- Paul J Kenny
- Department of Neuropharmacology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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14
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Lu L, Grimm JW, Hope BT, Shaham Y. Incubation of cocaine craving after withdrawal: a review of preclinical data. Neuropharmacology 2004; 47 Suppl 1:214-26. [PMID: 15464139 DOI: 10.1016/j.neuropharm.2004.06.027] [Citation(s) in RCA: 336] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2004] [Revised: 06/02/2004] [Accepted: 06/30/2004] [Indexed: 10/26/2022]
Abstract
Using a rat model of drug craving and relapse, we recently found that cocaine seeking induced by re-exposure to drug-associated cues progressively increases over the first 2 months after withdrawal from cocaine self-administration, suggesting that drug craving incubates over time [Nature 412 (2001) 141]. Here, we summarize data from studies that further characterized this incubation phenomenon and briefly discuss its implications for drug addiction. The main findings of our ongoing research are: 1. Incubation of cocaine craving is long-lasting, but not permanent: cocaine seeking induced by exposure to cocaine cues remains elevated for up to 3 months of withdrawal, but decreases after 6 months. 2. Incubation of reward craving is not drug specific: sucrose seeking induced by re-exposure to the reward cues also increases after withdrawal, but for a time period that is shorter than that of cocaine. 3. Incubation of cocaine craving is not evident after acute re-exposure to cocaine itself: cocaine seeking induced by cocaine priming injections remains essentially unchanged over the first 6 months of withdrawal. 4. Incubation of cocaine craving after withdrawal is associated with increases in the levels of brain-derived neurotrophic factor (BDNF) in mesolimbic dopamine areas.
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Affiliation(s)
- Lin Lu
- Behavioral Neuroscience Branch, IRP/NIDA/NIH/DHHS, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA
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Semenova S, Bespalov A, Markou A. Decreased prepulse inhibition during nicotine withdrawal in DBA/2J mice is reversed by nicotine self-administration. Eur J Pharmacol 2003; 472:99-110. [PMID: 12860478 DOI: 10.1016/s0014-2999(03)01904-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We characterized spontaneous and mecamylamine-precipitated nicotine withdrawal using intravenous nicotine self-administration, the acoustic startle response, prepulse inhibition and somatic signs of withdrawal in DBA/2J mice. Nicotine dependence was induced by continuous nicotine infusion through osmotic minipumps. Nicotine self-administration was studied before and after the induction of dependence. The initial test revealed significant nicotine self-administration at the 0.048 microg/infusion dose. During the second self-administration test, saline-treated mice exhibited increased aversiveness of response-contingent infusions of high nicotine doses; these changes were not seen in the nicotine-treated animals reflecting tolerance to nicotine's effects. Neither mecamylamine administration nor spontaneous withdrawal affected the expression of somatic signs, except that increases in jumping were observed during spontaneous withdrawal. Finally, nicotine withdrawal increased general activity in the startle chambers when no stimuli were presented, possibly reflecting increased body tremor and/or agitation, and decreased prepulse inhibition reflecting a sensorimotor gating deficit; the last two effects were reversed by nicotine self-administration. Thus, nicotine withdrawal results in modest, but yet detectable, changes in the behavior of mice.
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Affiliation(s)
- Svetlana Semenova
- Department of Neuropharmacology, CVN-7, The Scripps Research Institute, 10550 North Torrey Pines Rd., La Jolla, CA 92037, USA
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