1
|
Siviy SM, Martin MA, Campbell CM. Noradrenergic modulation of play in Sprague-Dawley and F344 rats. Psychopharmacology (Berl) 2023:10.1007/s00213-023-06419-2. [PMID: 37428218 DOI: 10.1007/s00213-023-06419-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 07/03/2023] [Indexed: 07/11/2023]
Abstract
RATIONALE For many mammals, engaging in social play behavior as a juvenile is important for cognitive, social, and emotional health as an adult. A playful phenotype reflects a dynamic interplay between genetic framework and experiences that operate on hard-wired brain systems so the relative lack of play in an otherwise playful species may be useful for identifying neural substrates that modulate play behavior. The inbred F344 rat has been identified as a strain that is consistently less playful than other strains commonly used in behavioral research. Norepinephrine (NE) acting on alpha-2 receptors has an inhibitory effect on play and F344 rats differ from a number of other strains in NE functioning. As such, the F344 rat may be particularly useful for gaining insight into NE involvement in play. OBJECTIVE The objective of this study was to determine whether the F344 rat is differentially sensitive to compounds that affect NE functioning and that are known to affect play behavior. METHODS Using pouncing and pinning to quantify play, the effects of the NE reuptake inhibitor atomoxetine, the NE alpha-2 receptor agonist guanfacine, and the NE alpha-2 receptor antagonist RX821002 on play behavior were assessed in juvenile Sprague-Dawley (SD) and F344 rats. RESULTS Atomoxetine and guanfacine reduced play in both SD and F344 rats. RX821002 increased pinning to a comparable extent in both strains but F344 rats were more sensitive to the play-enhancing effects of RX821002 on pounces. CONCLUSIONS Strain differences in NE alpha-2 receptor dynamics may contribute to the lower levels of play in F344 rats.
Collapse
Affiliation(s)
- Stephen M Siviy
- Department of Psychology, Gettysburg College, Gettysburg, PA, 17325, USA.
| | - Michelle A Martin
- Department of Psychology, Gettysburg College, Gettysburg, PA, 17325, USA
| | - Celeste M Campbell
- Department of Psychology, Gettysburg College, Gettysburg, PA, 17325, USA
| |
Collapse
|
2
|
Panfil K, Small R, Kirkpatrick K. Effects of methylphenidate on impulsive choice and delay aversion in Lewis rats. Behav Pharmacol 2023; 34:169-Btii. [PMID: 36752349 PMCID: PMC10006322 DOI: 10.1097/fbp.0000000000000719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Attention-deficit/hyperactivity disorder (ADHD), a common behavioral disorder in children and young adults, is characterized by symptoms of impulsivity, inattention, and hyperactivity. The purpose of this study was to evaluate the Lewis rat strain as a model of ADHD by testing their impulsive choices. Lewis rats were compared to their source strain, the Wistar rat, on an impulsive choice task. Rats completed the tasks on and off methylphenidate, a commonly prescribed medication for ADHD. Off methylphenidate, Lewis rats made more impulsive choices than Wistar rats. Analyses of acquisition of choice behavior suggested that both strains were able to discriminate reward sizes, but Lewis rats still chose the smaller-sooner option more than the larger-later (LL) option when the delays to reward were the same. This may be due to an aversion to the LL lever, which was associated with the longest delays to reward. Higher doses of methylphenidate increased LL choices in Lewis rats but decreased LL choices in Wistar rats. Altogether, these results suggest Lewis rats may be a viable model for ADHD in individuals whose symptoms are characterized by impulsive choices.
Collapse
Affiliation(s)
- Kelsey Panfil
- Department of Psychological Sciences, Kansas State University, Manhattan, Kansas, USA
| | | | | |
Collapse
|
3
|
“Wait and See”: Effects of Matching Visual Stimulation on Impulsive Behavior during an Adaptation of Flora et al.’s (1992) Choice Task. PSYCHOLOGICAL RECORD 2023. [DOI: 10.1007/s40732-023-00536-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
|
4
|
Steep Discounting of Future Rewards as an Impulsivity Phenotype: A Concise Review. Curr Top Behav Neurosci 2020; 47:113-138. [PMID: 32236897 DOI: 10.1007/7854_2020_128] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This chapter provides an overview over the behavioral economic index of impulsivity known as delay discounting. Specifically, delay discounting refers to an individual's preference for smaller immediate rewards over a larger delayed rewards. The more precipitously an individual discounts future rewards, the more impulsive they are considered to be. First, the chapter reviews the nature of delay discounting as a psychological process and juxtaposes it with nominally similar processes, including other facets of impulsivity. Second, the chapter reviews the links between delay discounting and numerous health behaviors, including addiction, attention deficit/hyperactivity disorder, and obesity. Third, the determinants of individual variation in delay discounting are discussed, including both genetic and environmental contributions. Finally, the chapter evaluates delay discounting as a potentially modifiable risk factor and the status of clinical interventions designed to reduce delay discounting to address deficits in self-control in a variety of maladaptive behaviors.
Collapse
|
5
|
Differential effects of d-amphetamine and atomoxetine on risk-based decision making of Lewis and Fischer 344 rats. Behav Pharmacol 2019; 30:605-616. [PMID: 31503070 DOI: 10.1097/fbp.0000000000000500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Individuals with attention-deficit/hyperactivity disorder tend to make risker choices during probabilistic-discounting procedures. Thus, how common attention-deficit/hyperactivity disorder medications affect probabilistic discounting is of interest. In general, d-amphetamine increases risk-taking while atomoxetine has produced mixed effects in rats. Results from previous studies may result from genetic factors. Lewis and F344 rats have neurochemical differences that may be relevant to probabilistic discounting and how drugs affect such behavior. In this study, we evaluated dose-dependent effects of d-amphetamine and atomoxetine on probabilistic discounting of Lewis and F344. Male Lewis and F344 chose between one food pellet delivered 100% of the time and three food pellets delivered following decreasing probabilities of delivery (i.e. 100%, 66.7%, 33.3%, 16.5%, and 8.25%). Saline, d-amphetamine (0.1-1.8 mg/kg), and atomoxetine (0.1-7.8 mg/kg) were tested acutely. Lewis and F344 did not differ in choice at baseline. d-Amphetamine increased risky choice for both rat strains at low-to-moderate doses, although it did so at a lower dose (0.1 and 0.3 mg/kg) for F344 as compared to Lewis (0.3 mg/kg only). At high doses (1.0 and 1.8 mg/kg), d-amphetamine disrupted choice, increased frequencies of omitted trials, and reduced reinforcer sensitivity. Although atomoxetine increased frequencies of omitted trials at high doses (5.6 and 7.8 mg/kg), it had no effect on probabilistic discounting for either rat strain. Although Lewis and F344 differ in various types of impulsivity (i.e. motor, choice), with Lewis being the more impulsive of the two, the present results suggest that Lewis and F344 do not differ in risk-based decision-making. Effects of d-amphetamine on probabilistic discounting may be biology-dependent and differ from effects of atomoxetine.
Collapse
|
6
|
Genomic basis of delayed reward discounting. Behav Processes 2019; 162:157-161. [PMID: 30876880 DOI: 10.1016/j.beproc.2019.03.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 03/04/2019] [Accepted: 03/09/2019] [Indexed: 02/07/2023]
Abstract
Delayed reward discounting (DRD) is a behavioral economic measure of impulsivity, reflecting how rapidly a reward loses value based on its temporal distance. In humans, more impulsive DRD is associated with susceptibility to a number of psychiatric diseases (e.g., addiction, ADHD), health outcomes (e.g., obesity), and lifetime outcomes (e.g., educational attainment). Although the determinants of DRD are both genetic and environmental, this review focuses on its genetic basis. Both rodent studies using inbred strains and human twin studies indicate that DRD is moderately heritable, a conclusion that was further supported by a recent human genome-wide association study (GWAS) that used single nucleotide polymorphisms (SNP) to estimate heritability. The GWAS of DRD also identified genetic correlations with psychiatric diagnoses, health outcomes, and measures of cognitive performance. Future research priorities include rodent studies probing putative genetic mechanisms of DRD and human GWASs using larger samples and non-European cohorts. Continuing to characterize genomic influences on DRD has the potential to yield important biological insights with implications for a variety of medically and socially important outcomes.
Collapse
|
7
|
MacKillop J, Gray JC, Weafer J, Sanchez-Roige S, Palmer AA, de Wit H. Genetic influences on delayed reward discounting: A genome-wide prioritized subset approach. Exp Clin Psychopharmacol 2019; 27:29-37. [PMID: 30265060 PMCID: PMC6908809 DOI: 10.1037/pha0000227] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Delayed reward discounting (DRD) is a behavioral economic measure of impulsivity that has been consistently associated with addiction. It has also been identified as a promising addiction endophenotype, linking specific sources of genetic variation to individual risk. A challenge in the studies to date is that levels of DRD are often confounded with prior drug use, and previous studies have also had limited genomic scope. The current investigation sought to address these issues by studying DRD in healthy young adults with low levels of substance use (N = 986; 62% female, 100% European ancestry) and investigating genetic variation genome-wide. The genome-wide approach used a prioritized subset design, organizing the tests into theoretically and empirically informed categories and apportioning power accordingly. Three subsets were used: (a) a priori loci implicated by previous studies; (b) high-value addiction (HVA) markers from the recently developed SmokeScreen array; and (c) an atheoretical genome-wide scan. Among a priori loci, a nominally significant association was present between DRD and rs521674 in ADRA2A. No significant HVA loci were detected. One statistically significant genome-wide association was detected (rs13395777, p = 2.8 × 10-8), albeit in an intergenic region of unknown function. These findings are generally not supportive of the previous candidate gene studies and suggest that DRD has a complex genetic architecture that will require considerably larger samples to identify genetic associations more definitively. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Collapse
Affiliation(s)
- James MacKillop
- Peter Boris Centre for Addictions Research, McMaster University/St. Joseph’s Healthcare Hamilton, Hamilton, ON L8P 3R2, Canada,Homewood Research Institute, Homewood Health Centre, Guelph, ON N1E 4J3 Canada
| | - Joshua C. Gray
- Department of Psychology, University of Georgia Athens, GA 30602, USA,Department of Psychiatry and Human Behavior, Brown University, Providence, RI 02912
| | - Jessica Weafer
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, Chicago, IL 60637, USA
| | - Sandra Sanchez-Roige
- Department of Psychiatry, University of California, San Diego, San Diego, CA 92093, USA
| | - Abraham A. Palmer
- Department of Psychiatry, University of California, San Diego, San Diego, CA 92093, USA,Institute for Genomic Medicine, University of California San Diego, La Jolla, CA 92103, USA
| | - Harriet de Wit
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, Chicago, IL 60637, USA
| |
Collapse
|
8
|
Soares AR, Esteves M, Moreira PS, Cunha AM, Guimarães MR, Carvalho MM, Raposo-Lima C, Morgado P, Carvalho AF, Coimbra B, Melo A, Rodrigues AJ, Salgado AJ, Pêgo JM, Cerqueira JJ, Costa P, Sousa N, Almeida A, Leite-Almeida H. Trait determinants of impulsive behavior: a comprehensive analysis of 188 rats. Sci Rep 2018; 8:17666. [PMID: 30518850 PMCID: PMC6281674 DOI: 10.1038/s41598-018-35537-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 10/02/2018] [Indexed: 11/09/2022] Open
Abstract
Impulsivity is a naturally occurring behavior that, when accentuated, can be found in a variety of neuropsychiatric disorders. The expression of trait impulsivity has been shown to change with a variety of factors, such as age and sex, but the existing literature does not reflect widespread consensus regarding the influence of modulating effects. We designed the present study to investigate, in a cohort of significant size (188 rats), the impact of four specific parameters, namely sex, age, strain and phase of estrous cycle, using the variable delay-to-signal (VDS) task. This cohort included (i) control animals from previous experiments; (ii) animals specifically raised for this study; and (iii) animals previously used for breeding purposes. Aging was associated with a general decrease in action impulsivity and an increase in delay tolerance. Females generally performed more impulsive actions than males but no differences were observed regarding delay intolerance. In terms of estrous cycle, no differences in impulsive behavior were observed and regarding strain, Wistar Han animals were, in general, more impulsive than Sprague-Dawley. In addition to further confirming, in a substantial study cohort, the decrease in impulsivity with age, we have demonstrated that both the strain and sex influences modulate different aspects of impulsive behavior manifestations.
Collapse
Affiliation(s)
- Ana Rosa Soares
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Madalena Esteves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Pedro Silva Moreira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Ana Margarida Cunha
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Marco Rafael Guimarães
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Miguel Murteira Carvalho
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.,Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, Trondheim, Norway
| | - Catarina Raposo-Lima
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Pedro Morgado
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Ana Franky Carvalho
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.,Department of General Surgery, Hospital of Braga, Braga, Portugal
| | - Bárbara Coimbra
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - António Melo
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Ana João Rodrigues
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - António José Salgado
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - José Miguel Pêgo
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - João José Cerqueira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Patrício Costa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Armando Almeida
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Hugo Leite-Almeida
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal. .,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.
| |
Collapse
|
9
|
Renee Renda C, Rung JM, Hinnenkamp JE, Lenzini SN, Madden GJ. Impulsive choice and pre-exposure to delays: iv. effects of delay- and immediacy-exposure training relative to maturational changes in impulsivity. J Exp Anal Behav 2018; 109:587-599. [PMID: 29683190 DOI: 10.1002/jeab.432] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Accepted: 04/02/2018] [Indexed: 12/31/2022]
Abstract
Impulsive choice describes preference for smaller, sooner rewards over larger, later rewards. Excessive delay discounting (i.e., rapid devaluation of delayed rewards) underlies some impulsive choices, and is observed in many maladaptive behaviors (e.g., substance abuse, gambling). Interventions designed to reduce delay discounting may provide therapeutic gains. One such intervention provides rats with extended training with delayed reinforcers. When compared to a group given extended training with immediate reinforcers, delay-exposed rats make significantly fewer impulsive choices. To what extent is this difference due to delay-exposure training shifting preference toward self-control or immediacy-exposure training (the putative control group) shifting preference toward impulsivity? The current study compared the effects of delay- and immediacy-exposure training to a no-training control group and evaluated within-subject changes in impulsive choice across 51 male Wistar rats. Delay-exposed rats made significantly fewer impulsive choices than immediacy-exposed and control rats. Between-group differences in impulsive choice were not observed in the latter two groups. While delay-exposed rats showed large, significant pre- to posttraining reductions in impulsive choice, immediacy-exposed and control rats showed small reductions in impulsive choice. These results suggest that extended training with delayed reinforcers reduces impulsive choice, and that extended training with immediate reinforcers does not increase impulsive choice.
Collapse
|
10
|
Abstract
Impulsive choice underlies several psychological disorders and can be assessed in laboratory rats using delay-discounting tasks, in which choice is for either one food pellet immediately or three food pellets after a delay. Choice for the smaller, immediate reinforcer is considered the impulsive choice. Lewis (LEW) and Fischer 344 (F344) rats differ in the number of impulsive choices made during this task when singly housed, with LEW choosing the impulsive option more often. Due to increasing recommendations to provide environmental enrichment as a component of animal-husbandry practices, a systematic replication of two previous studies was conducted using pair-housed LEW and F344. Delay discounting was assessed with pair-housed LEW and F344 and compared to previous data from singly housed LEW and F344 collected from the same laboratory. Results showed that differences in impulsive choice between the two strains were attenuated with pair housing. The main result driving this change appears to be an increase in impulsive choice in pair-housed F344 relative to singly housed F344.
Collapse
|
11
|
Ozga JE, Anderson KG. Reduction in delay discounting due to nicotine and its attenuation by cholinergic antagonists in Lewis and Fischer 344 rats. Psychopharmacology (Berl) 2018; 235:155-168. [PMID: 28971227 PMCID: PMC8130887 DOI: 10.1007/s00213-017-4752-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/20/2017] [Indexed: 02/07/2023]
Abstract
RATIONALE Nicotine acts as an agonist for nicotinic acetylcholine receptors (nAChRs), and mecamylamine, a nonselective nAChR antagonist, attenuates effects of nicotine on delay discounting in some rat strains; whether nicotine's attenuation is specific to nAChR antagonism is unknown. OBJECTIVE During experiment 1, we evaluated dose-dependent effects of nicotine on delay discounting of pair-housed Lewis (LEW) and Fischer 344 (F344) rats. During experiment 2, we examined the sensitivity of nicotine's effects on delay discounting to pharmacological antagonism of nAChRs or muscarinic AChRs (mAChRs). MATERIALS AND METHODS Male LEW and F344 were trained to choose between one food pellet delivered immediately and three food pellets delivered after an increasing delay. During experiment 1, saline and nicotine (0.1-1.0 mg/kg) were tested acutely. During experiment 2, mecamylamine (0.25-1.0 mg/kg) or a nonselective mAChR antagonist, scopolamine (0.01-0.056 mg/kg), was administered prior to nicotine administration. RESULTS Nicotine dose dependently reduced delay discounting for both rat strains, and no strain differences were observed (ΔAUC = + 107% for 1.0 mg/kg and + 69.6% for 0.3 mg/kg relative to saline). At some doses, pretreatment with mecamylamine (range ΔAUC = - 27.6 to - 7.3%) or scopolamine (range ΔAUC = - 0.74 to - 51.6%) significantly attenuated the nicotine-induced reduction in some measures of delay discounting for both strains. CONCLUSIONS Results from experiment 1 suggest that when LEW and F344 are pair housed, there are no strain differences in delay discounting in response to nicotine. Results from experiment 2 suggest that attenuation of nicotine's effects on delay discounting may not be specific to nAChR antagonism.
Collapse
Affiliation(s)
- Jenny E. Ozga
- Department of Psychology, West Virginia University, Morgantown, WV 26505, USA
| | - Karen G. Anderson
- Department of Psychology, West Virginia University, Morgantown, WV 26505, USA
| |
Collapse
|
12
|
Brewer A, Johnson P, Stein J, Schlund M, Williams DC. Aversive properties of negative incentive shifts in Fischer 344 and Lewis rats. Behav Brain Res 2016; 319:174-180. [PMID: 27864048 DOI: 10.1016/j.bbr.2016.11.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 11/07/2016] [Accepted: 11/13/2016] [Indexed: 10/20/2022]
Abstract
Research on incentive contrast highlights that reward value is not absolute but rather is based upon comparisons we make to rewards we have received and expect to receive. Both human and nonhuman studies on incentive contrast show that shifting from a larger more-valued reward to a smaller less-valued reward is associated with long periods of nonresponding - a negative contrast effect. In this investigation, we used two different genetic rat strains, Fischer 344 and Lewis rats that putatively differ in their sensitivity to aversive stimulation, to assess the aversive properties of large-to-small reward shifts (negative incentive shifts). Additionally, we examined the extent to which increasing cost (fixed-ratio requirements) modulates negative contrast effects. In the presence of a cue that signaled the upcoming reward magnitude, lever pressing was reinforced with one of two different magnitudes of food (large or small). This design created two contrast shifts (small-to-large, large-to-small) and two shifts used as control conditions (small-to-small, large-to-large). Results showed a significant interaction between rat strain and cost requirements only during the negative incentive shift with the emotionally reactive Fischer 344 rats exhibiting significantly longer response latencies with increasing cost, highlighting greater negative contrast. These findings are more consistent with emotionality accounts of negative contrast and results of neurophysiological research that suggests shifting from a large to a small reward is aversive. Findings also highlight how subjective reward value and motivation is a product of gene-environment interactions.
Collapse
Affiliation(s)
| | | | - Jeff Stein
- Virginia Tech Carillion Research Institute, Roanoke, VA, USA
| | | | | |
Collapse
|
13
|
Cadoni C. Fischer 344 and Lewis Rat Strains as a Model of Genetic Vulnerability to Drug Addiction. Front Neurosci 2016; 10:13. [PMID: 26903787 PMCID: PMC4746315 DOI: 10.3389/fnins.2016.00013] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/11/2016] [Indexed: 01/02/2023] Open
Abstract
Today it is well acknowledged that both nature and nurture play important roles in the genesis of psychopathologies, including drug addiction. Increasing evidence suggests that genetic factors contribute for at least 40–60% of the variation in liability to drug dependence. Human genetic studies suggest that multiple genes of small effect, rather than single genes, contribute to the genesis of behavioral psychopathologies. Therefore, the use of inbred rat strains might provide a valuable tool to identify differences, linked to genotype, important in liability to addiction and related disorders. In this regard, Lewis and Fischer 344 inbred rats have been proposed as a model of genetic vulnerability to drug addiction, given their innate differences in sensitivity to the reinforcing and rewarding effects of drugs of abuse, as well their different responsiveness to stressful stimuli. This review will provide evidence in support of this model for the study of the genetic influence on addiction vulnerability, with particular emphasis on differences in mesolimbic dopamine (DA) transmission, rewarding and emotional function. It will be highlighted that Lewis and Fischer 344 rats differ not only in several indices of DA transmission and adaptive changes following repeated drug exposure, but also in hypothalamic-pituitary-adrenal (HPA) axis responsiveness, influencing not only the ability of the individual to cope with stressful events, but also interfering with rewarding and motivational processes, given the influence of corticosteroids on dopamine neuron functionality. Further differences between the two strains, as impulsivity or anxiousness, might contribute to their different proneness to addiction, and likely these features might be linked to their different DA neurotransmission plasticity. Although differences in other neurotransmitter systems might deserve further investigation, results from the reviewed studies might open new vistas in understanding aberrant deviations in reward and motivational functions.
Collapse
Affiliation(s)
- Cristina Cadoni
- Institute of Neuroscience, Cagliari Section, Department of Biomedical Sciences, National Research Council of ItalyCagliari, Italy; Centre of Excellence "Neurobiology of Dependence", University of CagliariCagliari, Italy
| |
Collapse
|
14
|
Valenza M, Picetti R, Yuferov V, Butelman ER, Kreek MJ. Strain and cocaine-induced differential opioid gene expression may predispose Lewis but not Fischer rats to escalate cocaine self-administration. Neuropharmacology 2016; 105:639-650. [PMID: 26777278 DOI: 10.1016/j.neuropharm.2016.01.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/11/2015] [Accepted: 01/03/2016] [Indexed: 11/24/2022]
Abstract
The aim of the present study was to investigate alterations in gene expression of opioid system components induced by extended access (18 h) cocaine self-administration and to determine the impact of genetic background in the vulnerability to escalate cocaine intake. Comparing two inbred rat strains, we previously reported that Lewis rats progressively escalated cocaine consumption compared to Fischer rats, in a new translational model of intravenous cocaine self-administration, which included 14 sessions of 18-h operant sessions in which rats were allowed to select the cocaine unit dose to self-administer. We compare here Fischer and Lewis rats in the gene expression of endogenous opioid peptides (Pomc, Penk, Pdyn) and cognate receptors (Oprm, Oprk and Oprd) in reward-related brain regions, after exposure to either cocaine self-administration or yoked-saline, in the aforementioned translational paradigm. We performed a correlation analysis between the mRNA level, found in the Dorsal Striatum (DS), Nucleus accumbens (NAcc) shell and core respectively, and individual cocaine intake. Our findings show that the gene expression of all the aforementioned opioid genes exhibit strain-dependent differences in the DS, in absence of cocaine exposure. Also, different strain-specific cocaine-induced mRNA expression of Oprm and Oprk was found in DS. Only few differences were found in the ventral parts of the striatum. Moreover, gene expression level of Pdyn, Penk, Oprk, and Oprm in the DS was significantly correlated with cocaine intake only in Fischer rats. Overall, these data shed light on potential genetic differences which may predispose of subjects to initiate and escalate cocaine consumption.
Collapse
Affiliation(s)
- Marta Valenza
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA.
| | - Roberto Picetti
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA; Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, UK
| | - Vadim Yuferov
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - Eduardo R Butelman
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| | - Mary Jeanne Kreek
- Laboratory of the Biology of Addictive Diseases, The Rockefeller University, New York, NY, USA
| |
Collapse
|
15
|
Peterson JR, Hill CC, Marshall AT, Stuebing SL, Kirkpatrick K. I can't wait: Methods for measuring and moderating individual differences in impulsive choice. ACTA ACUST UNITED AC 2015; 13:89-99. [PMID: 27695664 DOI: 10.1515/jafio-2015-0024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Impulsive choice behavior occurs when individuals make choices without regard for future consequences. This behavior is often maladaptive and is a common symptom in many disorders, including drug abuse, compulsive gambling, and obesity. Several proposed mechanisms may influence impulsive choice behavior. These mechanisms provide a variety of pathways that may provide the basis for individual differences that are often evident when measuring choice behavior. This review provides an overview of these different pathways to impulsive choice, and the behavioral intervention strategies being developed to moderate impulsive choice. Because of the compelling link between impulsive choice behavior and the near-epidemic pervasiveness of obesity in the United States, we focus on the relationship between impulsive choice behavior and obesity as a test case for application of the multiple pathways approach. Choosing immediate gratification over healthier long term food choices is a contributing factor to the obesity crisis. Behavioral interventions can lead to more self controlled choices in a rat pre-clinical model, suggesting a possible gateway for translation to human populations. Designing and implementing effective impulsive choice interventions is crucial to improving the overall health and well-being of impulsive individuals.
Collapse
|
16
|
MacKillop J, Gray JC, Bidwell LC, Bickel WK, Sheffer CE, McGeary JE. Genetic influences on delay discounting in smokers: examination of a priori candidates and exploration of dopamine-related haplotypes. Psychopharmacology (Berl) 2015; 232. [PMID: 26220612 PMCID: PMC4845660 DOI: 10.1007/s00213-015-4029-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
RATIONALE Delay discounting is a behavioral economic index of impulsivity that reflects a person's relative preference for small immediate rewards versus larger delayed rewards. Elevated delay discounting is robustly linked to addictive disorders and has been increasingly investigated as a viable endophenotype for genetic influences on addiction. OBJECTIVE The aim of this study is to examine associations between delay discounting and two a priori loci, rs4680 in COMT and rs1800497 in ANKK1, and three exploratory haplotypes proximal to rs1800497 in a sample of daily smokers. METHODS Participants were 713 (60.2 % male) daily smokers of European ancestry who completed a delay discounting assessment and provided a DNA sample. RESULTS Significant associations were detected between greater discounting of medium magnitude rewards (~$55) and the G allele of rs4680, as well as the T allele of rs1800497. Exploratory haplotype analyses identified two haplotypes (rs1160467/rs1800497; rs6277/rs1079597) significantly associated with delay discounting rates. However, the rs1160467/rs1800497 haplotype associations appeared to be entirely attributable to variation in rs1800497, suggesting that the association of rs1800497 with discounting is best understood at the individual SNP level. Similarly, the rs6277/rs1079597 haplotype findings suggested that the association was specific to rs1079597. CONCLUSIONS This study provides further evidence that rs4680 and rs1800497 genotypes are significantly associated with delay discounting preferences and does so among smokers for the first time. The study also provides evidence of specificity for the rs1800497 association and identifies a novel locus, rs1079597, as a genetic contributor to higher delay discounting rates.
Collapse
Affiliation(s)
- James MacKillop
- Peter Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University/St. Joseph's Healthcare Hamilton, Hamilton, ON, Canada,
| | | | | | | | | | | |
Collapse
|
17
|
Gray JC, MacKillop J. Impulsive delayed reward discounting as a genetically-influenced target for drug abuse prevention: a critical evaluation. Front Psychol 2015; 6:1104. [PMID: 26388788 PMCID: PMC4554956 DOI: 10.3389/fpsyg.2015.01104] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/17/2015] [Indexed: 12/22/2022] Open
Abstract
This review evaluates the viability of delayed reward discounting (DRD), an index of how much an individual devalues a future reward based on its delay in time, for genetically-informed drug abuse prevention. A review of the literature suggests that impulsive DRD is robustly associated with drug addiction and meets most of the criteria for being an endophenotype, albeit with mixed findings for specific molecular genetic influences. Several modes of experimental manipulation have been demonstrated to reduce DRD acutely. These include behavioral strategies, such as mindfulness, reward bundling, and episodic future thinking; pharmacological interventions, including noradrenergic agonists, adrenergic agonists, and multiple monoamine agonists; and neuromodulatory interventions, such as transcranial magnetic stimulation and transcranial direct current stimulation. However, the generalization of these interventions to positive clinical outcomes remains unclear and no studies to date have examined interventions on DRD in the context of prevention. Collectively, these findings suggest it would be premature to target DRD for genetically-informed prevention. Indeed, given the evidence of environmental contributions to impulsive DRD, whether genetically-informed secondary prevention would ever be warranted is debatable. Progress in identifying polymorphisms associated with DRD profiles could further clarify the underlying biological systems for pharmacological and neuromodulatory interventions, and, as a qualitatively different risk factor from existing prevention programs, impulsive DRD is worthy of investigation at a more general level as a novel and promising drug abuse prevention target.
Collapse
Affiliation(s)
- Joshua C Gray
- Department of Psychology, University of Georgia , Athens, GA, USA
| | - James MacKillop
- Department of Psychology, University of Georgia , Athens, GA, USA ; Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton , Hamilton, ON, Canada
| |
Collapse
|
18
|
|
19
|
Smith AP, Marshall AT, Kirkpatrick K. Mechanisms of impulsive choice: II. Time-based interventions to improve self-control. Behav Processes 2015; 112:29-42. [PMID: 25444771 PMCID: PMC4314470 DOI: 10.1016/j.beproc.2014.10.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 09/29/2014] [Accepted: 10/22/2014] [Indexed: 02/03/2023]
Abstract
Impulsive choice behavior has been proposed as a primary risk factor for other maladaptive behaviors (e.g., gambling, substance abuse). Recent research has suggested that timing processes may play a key role in impulsive choice behavior, and could provide an avenue for altering impulsive choice. Accordingly, the current experiments assessed a set of time-based behavioral interventions to increase self-control while simultaneously assessing effects on timing processes within the impulsive choice task. Three experiments assessed temporal interventions using a differential reinforcement of low rates task (Experiment 1) and exposure to either a variable or fixed interval schedule (Experiments 2-3). The efficacy of the interventions was assessed in Sprague-Dawley (Experiments 1-2) and Lewis (Experiment 3) rat strains. Impulsive choice behavior was assessed by measuring preferences of a smaller-sooner (SS) versus a larger-later (LL) reward, while timing of the SS and LL durations was measured during peak trials within the impulsive choice procedure. The rats showed an increased preference for the LL following all three time-based interventions and also displayed increased temporal precision. These results add to the increasing evidence that supports a possible role for temporal processing in impulsive choice behavior and supply novel behavioral interventions to decrease impulsive behavior.
Collapse
Affiliation(s)
- Aaron P Smith
- Department of Psychological Sciences, Kansas State University, 492 Bluemont Hall, 1100 Mid-Campus, Manhattan, KS 66506-5302, United States
| | - Andrew T Marshall
- Department of Psychological Sciences, Kansas State University, 492 Bluemont Hall, 1100 Mid-Campus, Manhattan, KS 66506-5302, United States
| | - Kimberly Kirkpatrick
- Department of Psychological Sciences, Kansas State University, 492 Bluemont Hall, 1100 Mid-Campus, Manhattan, KS 66506-5302, United States.
| |
Collapse
|
20
|
Gray JC, MacKillop J. Using Behavior Economics to Understand Alcohol Use Disorders: A Concise Review and Identification of Research Priorities. CURRENT ADDICTION REPORTS 2015; 2:68-75. [PMID: 27795939 DOI: 10.1007/s40429-015-0045-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We review recent advances in the application of behavioral economics to alcohol use disorders (AUDs). Specifically, we review individual differences in alcohol demand (i.e., the relative reinforcing value of alcohol) and delayed reward discounting (i.e., impulsive decision making) in relation to AUDs. Additionally, we review the efficacy of reinforcement-based clinical applications. What emerges from the literature is an extensive body of cross-sectional research implicating alcohol demand and delayed reward discounting with alcohol misuse. However, more research is needed to examine these domains across the lifespan in order to understand their longitudinal trajectories. Similarly, clinical research is consistently supportive of reinforcement-based clinical interventions, but the number of randomized controlled trials to date is relatively small and there has been limited examination of the putative mechanisms of behavior change.
Collapse
Affiliation(s)
| | - James MacKillop
- Peter Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University / St Joseph's Healthcare Hamilton
| |
Collapse
|
21
|
Kirkpatrick K, Marshall AT, Smith AP. Mechanisms of Individual Differences in Impulsive and Risky Choice in Rats. COMPARATIVE COGNITION & BEHAVIOR REVIEWS 2015; 10:45-72. [PMID: 27695580 PMCID: PMC5045043 DOI: 10.3819/ccbr.2015.100003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Individual differences in impulsive and risky choice are key risk factors for a variety of maladaptive behaviors such as drug abuse, gambling, and obesity. In our rat model, ordered individual differences are stable across choice parameters, months of testing, and span a broad spectrum, suggesting that rats, like humans, exhibit trait-level impulsive and risky choice behaviors. In addition, impulsive and risky choices are highly correlated, suggesting a degree of correlation between these two traits. An examination of the underlying cognitive mechanisms has suggested an important role for timing processes in impulsive choice. In addition, in an examination of genetic factors in impulsive choice, the Lewis rat strain emerged as a possible animal model for studying disordered impulsive choice, with this strain demonstrating deficient delay processing. Early rearing environment also affected impulsive behaviors, with rearing in an enriched environment promoting adaptable and more self-controlled choices. The combined results with impulsive choice suggest an important role for timing and reward sensitivity in moderating impulsive behaviors. Relative reward valuation also affects risky choice, with manipulation of objective reward value (relative to an alternative reference point) resulting in loss chasing behaviors that predicted overall risky choice behaviors. The combined results are discussed in relation to domain-specific versus domain-general subjective reward valuation processes and the potential neural substrates of impulsive and risky choice.
Collapse
|
22
|
Marshall AT, Kirkpatrick K. Everywhere and everything: The power and ubiquity of time. INTERNATIONAL JOURNAL OF COMPARATIVE PSYCHOLOGY 2015; 28:http://escholarship.org/uc/item/8hg831n3. [PMID: 28392622 PMCID: PMC5382961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023] Open
Abstract
Anticipatory timing plays a critical role in many aspects of human and non-human animal behavior. Timing has been consistently observed in the range of milliseconds to hours, and demonstrates a powerful influence on the organization of behavior. Anticipatory timing is acquired early in associative learning and appears to guide association formation in important ways. Importantly, timing participates in regulating goal-directed behaviors in many schedules of reinforcements, and plays a critical role in value-based decision making under concurrent schedules. In addition to playing a key role in fundamental learning processes, timing often dominates when temporal cues are available concurrently with other stimulus dimensions. Such control by the passage of time has even been observed when other cues provide more accurate information and can lead to sub-optimal behaviors. The dominance of temporal cues in governing anticipatory behavior suggests that time may be inherently more salient than many other stimulus dimensions. Discussions of the interface of the timing system with other cognitive processes are provided to demonstrate the powerful and primitive nature of time as a stimulus dimension.
Collapse
|
23
|
Effects of acute and repeated nicotine administration on delay discounting in Lewis and Fischer 344 rats. Behav Pharmacol 2014; 21:754-64. [PMID: 20944502 DOI: 10.1097/fbp.0b013e328340a050] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Biological differences may underlie individual differences in impulsive behavior, such as choice for a smaller, more immediate reinforcer over a larger, more delayed reinforcer. Repeated exposure to drugs of abuse may have different effects on such behavior. To evaluate the acute and repeated effects of nicotine on impulsive choice, two strains of rats that have been shown to differ in impulsive choice were tested in a delay-discounting paradigm. Eight Lewis and eight Fischer 344 rats were allowed to choose between one food pellet delivered immediately and three food pellets delivered after a delay. The delay systematically increased in blocks of trials within each session, and the delay value at which the choice for the two alternatives was equal (i.e. the indifference point) was interpolated. Effects of nicotine (0.1-1.0 mg/kg, subcutaneous) on percent choice and indifference points were determined during the acute-testing phase and during the redetermination of effects of each dose after at least 30 sessions of repeated 1.0 mg/kg nicotine exposure. The Lewis rats had shorter indifference points (i.e. made fewer larger-reinforcer choices) compared with the Fischer 344 rats. Acute nicotine administration increased the mean larger-reinforcer choices at the 0.3 mg/kg dose in the Lewis rats and at the 1.0 mg/kg dose in the Fischer 344 rats. After repeated exposure to nicotine, indifference points returned to near-baseline (predrug) levels for both the strains. Strain differences were observed in the rates of delay discounting, and nicotine may decrease the impulsive choice acutely, but this effect does not seem to be long lasting.
Collapse
|
24
|
Peterson JR, Hill CC, Kirkpatrick K. Measurement of impulsive choice in rats: same- and alternate-form test-retest reliability and temporal tracking. J Exp Anal Behav 2014; 103:166-79. [PMID: 25490901 DOI: 10.1002/jeab.124] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/16/2014] [Indexed: 11/08/2022]
Abstract
Impulsive choice is typically measured by presenting smaller-sooner (SS) versus larger-later (LL) rewards, with biases towards the SS indicating impulsivity. The current study tested rats on different impulsive choice procedures with LL delay manipulations to assess same-form and alternate-form test-retest reliability. In the systematic-GE procedure (Green & Estle, 2003), the LL delay increased after several sessions of training; in the systematic-ER procedure (Evenden & Ryan, 1996), the delay increased within each session; and in the adjusting-M procedure (Mazur, 1987), the delay changed after each block of trials within a session based on each rat's choices in the previous block. In addition to measuring choice behavior, we also assessed temporal tracking of the LL delays using the median times of responding during LL trials. The two systematic procedures yielded similar results in both choice and temporal tracking measures following extensive training, whereas the adjusting procedure resulted in relatively more impulsive choices and poorer temporal tracking. Overall, the three procedures produced acceptable same form test-retest reliability over time, but the adjusting procedure did not show significant alternate form test-retest reliability with the other two procedures. The results suggest that systematic procedures may supply better measurements of impulsive choice in rats.
Collapse
|
25
|
Friedel JE, DeHart WB, Madden GJ, Odum AL. Impulsivity and cigarette smoking: discounting of monetary and consumable outcomes in current and non-smokers. Psychopharmacology (Berl) 2014; 231:4517-26. [PMID: 24819731 PMCID: PMC4221621 DOI: 10.1007/s00213-014-3597-z] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 04/16/2014] [Indexed: 11/12/2022]
Abstract
RATIONALE In delay discounting, temporally remote rewards have less value. Cigarette smoking is associated with steeper discounting of delayed money. The generality of this to nonmonetary outcomes, however, is unknown. OBJECTIVES We sought to determine whether cigarette smokers also show steep discounting of other delayed outcomes. METHODS Sixty-five participants (32 smokers and 33 non-smokers) completed four delay-discounting tasks, each involving different hypothetical outcomes. In the monetary task, participants indicated their preference for a smaller amount of money available immediately (titrated across trials) and $100 awarded at delays ranging from 1 week to 25 years (tested in blocks). In the three other discounting tasks the larger-later reward was $100 worth of a favorite food, alcoholic drink, or a favorite form of entertainment. All other aspects of these discounting tasks were identical to the monetary discounting task. RESULTS As previously shown, smokers discounted delayed money more steeply than non-smokers did. In addition, smokers discounted delayed food and entertainment rewards more steeply than did nonsmokers. A person's discounting of one outcome was correlated with discounting of other outcomes. Non-smokers discounted money less steeply than all other outcomes; smokers discounted money significantly less than food. CONCLUSIONS When compared to nonsmokers, cigarette smokers more steeply discount several types of delayed outcomes. This result, together with the finding that cross-commodity discounting rates were correlated within subjects, suggests that delay discounting is a trait that extends across domains.
Collapse
Affiliation(s)
- Jonathan E. Friedel
- Department of Psychology, Utah State University, 2810 Old Main Hill, Logan, UT 84322 USA
| | - William B. DeHart
- Department of Psychology, Utah State University, 2810 Old Main Hill, Logan, UT 84322 USA
| | - Gregory J. Madden
- Department of Psychology, Utah State University, 2810 Old Main Hill, Logan, UT 84322 USA
| | - Amy L. Odum
- Department of Psychology, Utah State University, 2810 Old Main Hill, Logan, UT 84322 USA
| |
Collapse
|
26
|
Hamilton KR, Potenza MN, Grunberg NE. Lewis rats have greater response impulsivity than Fischer rats. Addict Behav 2014; 39:1565-1572. [PMID: 24613059 PMCID: PMC4222187 DOI: 10.1016/j.addbeh.2014.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 01/16/2014] [Accepted: 02/15/2014] [Indexed: 10/25/2022]
Abstract
Impulsivity, a tendency toward immediate action without consideration of future consequences, is associated with a wide array of problematic behaviors. Response impulsivity, a type of behaviorally-assessed impulsivity characterized by behavioral disinhibition, is also associated with health risk behaviors. Response impulsivity is distinct from choice impulsivity, which is characterized by intolerance for delay. Lewis rats have higher levels of choice impulsivity than Fischer rats (Anderson & Woolverton, 2005; Madden et al., 2008; Stein et al., 2012). However, no studies have examined whether Lewis and Fischer rats have different levels of response impulsivity. The present research examined response impulsivity in the two rat strains. Subjects were 16 male Lewis and Fischer rats. Rats' response impulsivity was measured using the Five Choice Serial Reaction Time Task (5-CSRTT). In addition, their locomotor activity was measured in locomotor activity chambers. Lewis rats had more premature responses than Fischer rats during the 5-CSRTT assessment [F(1, 14)=5.34, p<0.05], indicating higher levels of response impulsivity. Locomotor activity did not differ between rat strain groups [F(1, 14)=3.05, p=.10], suggesting that overall movement did not account for group differences in response impulsivity on the 5-CSRTT. It can be concluded from this research that Lewis rats have higher levels of response impulsivity than Fischer rats, and therefore provide a valid rat model of individual differences in impulsivity.
Collapse
Affiliation(s)
- Kristen R Hamilton
- Department of Medical & Clinical Psychology, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| | - Marc N Potenza
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06510, USA; Department of Neurobiology, Yale University School of Medicine, New Haven, CT 06510, USA; Child Study Center, Yale University School of Medicine, New Haven, CT 06510, USA.
| | - Neil E Grunberg
- Department of Medical & Clinical Psychology, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814, USA; Program in Neuroscience, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
| |
Collapse
|
27
|
Gray JC, MacKillop J. Genetic basis of delay discounting in frequent gamblers: examination of a priori candidates and exploration of a panel of dopamine-related loci. Brain Behav 2014; 4:812-21. [PMID: 25365808 PMCID: PMC4212112 DOI: 10.1002/brb3.284] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 08/05/2014] [Accepted: 08/11/2014] [Indexed: 01/19/2023] Open
Abstract
INTRODUCTION Delay discounting is a behavioral economic index of impulsivity that reflects preferences for small immediate rewards relative to larger delayed rewards. It has been consistently linked to pathological gambling and other forms of addictive behavior, and has been proposed to be a behavioral characteristic that may link genetic variation and risk of developing addictive disorders (i.e., an endophenotype). Studies to date have revealed significant associations with polymorphisms associated with dopamine neurotransmission. The current study examined associations between delay discounting and both previously linked variants and a novel panel of dopamine-related variants in a sample of frequent gamblers. METHODS Participants were 175 weekly gamblers of European ancestry who completed the Monetary Choice Questionnaire to assess delay discounting preferences and provided a DNA via saliva. RESULTS In a priori tests, two loci previously associated with delayed reward discounting (rs1800497 and rs4680) were not replicated, however, the long form of DRD4 VNTR was significantly associated with lower discounting of delayed rewards. Exploratory analysis of the dopamine-related panel revealed 11 additional significant associations in genes associated with dopamine synthesis, breakdown, reuptake, and receptor function (DRD3, SLC6A3, DDC, DBH, and SLC18A2). An aggregate genetic risk score from the nominally significant loci accounted for 17% of the variance in discounting. Mediational analyses largely supported the presence of indirect effects between the associated loci, delay discounting, and pathological gambling severity. CONCLUSIONS These findings do not replicate previously reported associations but identify several novel candidates and provide preliminary support for a systems biology approach to understand the genetic basis of delay discounting.
Collapse
Affiliation(s)
- Joshua C Gray
- Department of Psychology, University of Georgia Athens, Georgia
| | - James MacKillop
- Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University Hamilton, Ontario, Canada
| |
Collapse
|
28
|
Bari A, Robbins TW. Inhibition and impulsivity: Behavioral and neural basis of response control. Prog Neurobiol 2013; 108:44-79. [DOI: 10.1016/j.pneurobio.2013.06.005] [Citation(s) in RCA: 1193] [Impact Index Per Article: 108.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 05/24/2013] [Accepted: 06/26/2013] [Indexed: 11/17/2022]
|
29
|
Huskinson SL, Anderson KG. Effects of different fixed-ratio requirements on delay discounting in rats. Behav Processes 2013; 100:18-22. [PMID: 23891790 DOI: 10.1016/j.beproc.2013.07.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 07/06/2013] [Accepted: 07/06/2013] [Indexed: 11/16/2022]
Abstract
In delay discounting, choice is between two reinforcers that differ in amount and delay, and the subjective value of either reinforcer decreases as a function of delay to its receipt. The steepness of the discounting function is thought to reflect the degree of impulsive choice. Many factors can influence impulsive choice, including the addition of a constant delay or response requirement to the smaller sooner (SS) and larger later (LL) reinforcers. A delay-discounting procedure developed by Evenden and Ryan (1996) is commonly used in behavioral research, yet effects of adding a response requirement to both alternatives with this procedure has not been examined. If different delay-discounting procedures are measuring the same phenomenon, preference reversals should occur with the Evenden and Ryan procedure as they do with other procedures with an added response requirement. The current experiment used an Evenden and Ryan procedure, and choice was examined when the response requirement was a small, intermediate, and large fixed ratio (FR). Fewer LL choices occurred with the small FR, and more LL choices occurred with the intermediate and large FR. The present experiment extends preference-reversal findings to a different and commonly used delay-discounting procedure.
Collapse
|
30
|
Richards JB, Lloyd DR, Kuehlewind B, Militello L, Paredez M, Solberg Woods L, Palmer AA. Strong genetic influences on measures of behavioral-regulation among inbred rat strains. GENES BRAIN AND BEHAVIOR 2013; 12:490-502. [PMID: 23710681 DOI: 10.1111/gbb.12050] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 04/22/2013] [Accepted: 05/14/2013] [Indexed: 11/27/2022]
Abstract
A fundamental challenge for any complex nervous system is to regulate behavior in response to environmental challenges. Three measures of behavioral-regulation were tested in a panel of eight inbred rat strains. These measures were: (1) sensation seeking as assessed by locomotor response to novelty and the sensory reinforcing effects of light onset, (2) attention and impulsivity, as measured by a choice reaction time task and (3) impulsivity as measured by a delay discounting task. Deficient behavioral-regulation has been linked to a number of psychopathologies, including ADHD, Schizophrenia, Autism, drug abuse and eating disorders. Eight inbred rat strains (August Copenhagen Irish, Brown Norway, Buffalo, Fischer 344, Wistar Kyoto, Spontaneous Hypertensive Rat, Lewis, Dahl Salt Sensitive) were tested. With n = 9 for each strain, we observed robust strain differences for all tasks; heritability was estimated between 0.43 and 0.66. Performance of the eight inbred rat strains on the choice reaction time task was compared to the performance of outbred Sprague Dawley (n = 28) and Heterogeneous strain rats (n = 48). The results indicate a strong genetic influence on complex tasks related to behavioral-regulation and indicate that some of the measures tap common genetically driven processes. Furthermore, our results establish the potential for future studies aimed at identifying specific alleles that influence variability for these traits. Identification of such alleles could contribute to our understanding of the molecular genetic basis of behavioral-regulation, which is of fundamental importance and likely contributes to multiple psychiatric disorders.
Collapse
Affiliation(s)
- J B Richards
- Research Institute on Addictions, State University of New York at Buffalo, Buffalo, NY 14203, USA.
| | | | | | | | | | | | | |
Collapse
|
31
|
|
32
|
Garcia A, Kirkpatrick K. Impulsive choice behavior in four strains of rats: evaluation of possible models of Attention-Deficit/Hyperactivity Disorder. Behav Brain Res 2013; 238:10-22. [PMID: 23085479 PMCID: PMC3513624 DOI: 10.1016/j.bbr.2012.10.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 10/08/2012] [Accepted: 10/11/2012] [Indexed: 02/06/2023]
Abstract
Several studies have examined impulsive choice behavior in spontaneously hypertensive rats (SHRs) as a possible pre-clinical model for Attention-Deficit/Hyperactivity Disorder (ADHD). However, this strain was not specifically selected for the traits of ADHD and as a result their appropriateness as a model has been questioned. The present study investigated whether SHRs would exhibit impulsive behavior in comparison to their control strain, Wistar Kyoto (WKY) rats. In addition, we evaluated a strain that has previously shown high levels of impulsive choice, the Lewis (LEW) rats and compared them with their source strain, Wistar (WIS) rats. In the first phase, rats could choose between a smaller-sooner (SS) reward of 1 pellet after 10 s and a larger-later (LL) reward of 2 pellets after 30 s. Subsequently, the rats were exposed to increases in LL reward magnitude and SS delay. These manipulations were designed to assess sensitivity to magnitude and delay within the choice task to parse out possible differences in using the strains as models of specific deficits associated with ADHD. The SHR and WKY strains did not differ in their choice behavior under either delay or magnitude manipulations. In comparison to WIS, LEW showed deficits in choice behavior in the delay manipulation, and to a lesser extent in the magnitude manipulation. An examination of individual differences indicated that the SHR strain may not be sufficiently homogeneous in their impulsive choice behavior to be considered as a viable model for impulse control disorders such as ADHD. The LEW strain may be worthy of further consideration for their suitability as an animal model.
Collapse
Affiliation(s)
- Ana Garcia
- Kansas State University, Manhattan, KS 66506-5302, United States
| | | |
Collapse
|
33
|
Galtress T, Garcia A, Kirkpatrick K. Individual differences in impulsive choice and timing in rats. J Exp Anal Behav 2013; 98:65-87. [PMID: 22851792 DOI: 10.1901/jeab.2012.98-65] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 05/10/2012] [Indexed: 11/22/2022]
Abstract
Individual differences in impulsive choice behavior have been linked to a variety of behavioral problems including substance abuse, smoking, gambling, and poor financial decision-making. Given the potential importance of individual differences in impulsive choice as a predictor of behavioral problems, the present study sought to measure the extent of individual differences in a normal sample of hooded Lister rats. Three experiments utilized variations of a delay discounting task to measure the degree of variation in impulsive choice behavior across individual rats. The individual differences accounted for 22-55% of the variance in choice behavior across the three experiments. In Experiments 2 and 3, the individual differences were still apparent when behavior was measured across multiple choice points. Large individual differences in the rate of responding, and modest individual differences in timing of responding were also observed during occasional peak trials. The individual differences in timing and rate, however, did not correlate consistently with individual differences in choice behavior. This suggests that a variety of factors may affect choice behavior, response rate, and response timing.
Collapse
|
34
|
MacKillop J. Integrating behavioral economics and behavioral genetics: delayed reward discounting as an endophenotype for addictive disorders. J Exp Anal Behav 2012; 99:14-31. [PMID: 23344986 DOI: 10.1002/jeab.4] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 07/05/2012] [Indexed: 01/15/2023]
Abstract
Delayed reward discounting is a behavioral economic index of impulsivity, referring to how much an individual devalues a reward based on its delay in time. As a behavioral process that varies considerably across individuals, delay discounting has been studied extensively as a model for self-control, both in the general population and in clinical samples. There is growing interest in genetic influences on discounting and, in particular, the prospect of discounting as an endophenotype for addictive disorders (i.e., a heritable mechanism partially responsible for conferring genetic risk). This review assembles and critiques the evidence supporting this hypothesis. Via numerous cross-sectional studies and a small number of longitudinal studies, there is considerable evidence that impulsive discounting is associated with addictive behavior and appears to play an etiological role. Moreover, there is increasing evidence from diverse methodologies that impulsive delay discounting is temporally stable, heritable, and that elevated levels are present in nonaffected family members. These findings suggest that impulsive discounting meets the criteria for being considered an endophenotype. In addition, recent findings suggest that genetic variation related to dopamine neurotransmission is significantly associated with variability in discounting preferences. A significant caveat, however, is that the literature is modest in some domains and, in others, not all the findings have been supportive or consistent. In addition, important methodological considerations are necessary in future studies. Taken together, although not definitive, there is accumulating support for the hypothesis of impulsive discounting as an endophenotype for addictive behavior and a need for further systematic investigation.
Collapse
Affiliation(s)
- James MacKillop
- Department of Psychology, 100 Hooper St. University of Georgia, Athens, GA 30605, USA.
| |
Collapse
|
35
|
Stein JS, Pinkston JW, Brewer AT, Francisco MT, Madden GJ. Delay discounting in Lewis and Fischer 344 rats: steady-state and rapid-determination adjusting-amount procedures. J Exp Anal Behav 2012; 97:305-21. [PMID: 22693360 DOI: 10.1901/jeab.2012.97-305] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 02/28/2012] [Indexed: 02/04/2023]
Abstract
Lewis rats have been shown to make more impulsive choices than Fischer 344 rats in discrete-trial choice procedures that arrange fixed (i.e., nontitrating) reinforcement parameters. However, nontitrating procedures yield only gross estimates of preference, as choice measures in animal subjects are rarely graded at the level of the individual subject. The present study was designed to examine potential strain differences in delay discounting using an adjusting-amount procedure, in which distributed (rather than exclusive) choice is observed due to dynamic titration of reinforcer magnitude across trials. Using a steady-state version of the adjusting-amount procedure in which delay was manipulated between experimental conditions, steeper delay discounting was observed in Lewis rats compared to Fischer 344 rats; further, delay discounting in both strains was well described by the traditional hyperbolic discounting model. However, upon partial completion of the present study, a study published elsewhere (Wilhelm & Mitchell, 2009) demonstrated no difference in delay discounting between these strains with the use of a more rapid version of the adjusting-amount procedure (i.e., in which delay is manipulated daily). Thus, following completion of the steady-state assessment in the present study, all surviving Lewis and Fischer 344 rats completed an approximation of this rapid-determination procedure in which no strain difference in delay discounting was observed.
Collapse
|
36
|
Odum AL. Delay discounting: I'm a k, you're a k. J Exp Anal Behav 2012; 96:427-39. [PMID: 22084499 DOI: 10.1901/jeab.2011.96-423] [Citation(s) in RCA: 374] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Accepted: 07/29/2011] [Indexed: 10/28/2022]
Abstract
Delay discounting is the decline in the present value of a reward with delay to its receipt. Across a variety of species, populations, and reward types, value declines hyperbolically with delay. Value declines steeply with shorter delays, but more shallowly with longer delays. Quantitative modeling provides precise measures to characterize the form of the discount function. These measures may be regarded as higher-order dependent variables, intervening variables, or hypothetical constructs. I suggest the degree of delay discounting may be a personality trait. In the end, the ontological status of measures of delay discounting is irrelevant. Whatever delay discounting may be, its study has provided the field of behavior analysis and other areas measures with robust generality and predictive validity for a variety of significant human problems. Research on moderating the degree of delay discounting has the potential to produce substantial societal benefits.
Collapse
Affiliation(s)
- Amy L Odum
- Department of Psychology, Utah State University, Logan, UT 84322, USA.
| |
Collapse
|
37
|
Huskinson SL, Krebs CA, Anderson KG. Strain differences in delay discounting between Lewis and Fischer 344 rats at baseline and following acute and chronic administration of d-amphetamine. Pharmacol Biochem Behav 2012; 101:403-16. [PMID: 22342664 DOI: 10.1016/j.pbb.2012.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 01/29/2012] [Accepted: 02/05/2012] [Indexed: 10/14/2022]
Abstract
Stimulant drugs have been shown either to increase or decrease rates of delay discounting (impulsive choice). These mixed findings may result from genetic, neurochemical, or environmental factors. Lewis (LEW) and Fischer 344 (F344) rats have neurochemical and behavioral differences that may be relevant to delay discounting and were used to examine effects of acute and chronic administration of d-amphetamine (d-AMP) on impulsive choice using a within-session delay-discounting procedure. Male LEW (n=8) and F344 (n=8) rats chose between one food pellet delivered immediately and three food pellets delivered after an increasing delay. Saline and d-AMP (0.1, 0.3, 1.0, and 1.7 mg/kg) were tested acutely and during chronic d-AMP exposure. Choice for the larger reinforcer decreased as the delay to its presentation increased for both strains at baseline. LEW rats made more impulsive choices than F344 rats as indicated by shorter indifference points, and this is consistent with previous research. Acute administration of d-AMP dose dependently increased larger-reinforcer choice and area under the curve (AUC) for LEW, but not F344 rats. During chronic exposure to d-AMP, larger-reinforcer choice and AUC increased relative to acute administration for F344 rats responding in shorter delay series, but not for F344 rats responding in longer delay series or for LEW rats. Differential effects of acute and chronic administration of d-AMP on impulsive choice in LEW and F344 rats may be a result of various factors, including genetic, neurochemical, and environmental variables. Future research should attempt to tease apart the relative contribution of each of these factors on impulsive choice.
Collapse
Affiliation(s)
- Sally L Huskinson
- West Virginia University, Department of Psychology, P.O. Box 6040, Morgantown, WV 26506, United States
| | | | | |
Collapse
|
38
|
Delay discounting: trait variable? Behav Processes 2011; 87:1-9. [PMID: 21385637 DOI: 10.1016/j.beproc.2011.02.007] [Citation(s) in RCA: 254] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 02/15/2011] [Accepted: 02/16/2011] [Indexed: 11/20/2022]
Abstract
Delay discounting refers to the tendency for outcomes that are remote in time to have less value than more immediate outcomes. Steep discounting of delayed outcomes is associated with a variety of social maladies. The degree of sensitivity to delayed outcomes may be a stable and pervasive individual characteristic. In analyses of archival data, the present study found positive correlations between the degree of delay discounting for one outcome (as measured by the Area Under the Curve), and the degree of discounting for other outcomes. Along with additional evidence reviewed, these data suggest that delay discounting may be considered a personality trait. Recent research in epigenetics, neuroscience, and behavior suggests delay discounting may prove to be a beneficial target for therapeutic attempts to produce global reductions in impulsivity related to delay discounting.
Collapse
|
39
|
Mitchell SH. The genetic basis of delay discounting and its genetic relationship to alcohol dependence. Behav Processes 2011; 87:10-7. [PMID: 21354276 DOI: 10.1016/j.beproc.2011.02.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/17/2011] [Accepted: 02/17/2011] [Indexed: 12/20/2022]
Abstract
Delay discounting is steeper for individuals who drink heavily or are alcohol dependent, but the reasons for this are unclear. Given the substantial genetic component for alcohol dependence it is not unreasonable to ask whether discounting and alcohol dependence have a genetic relationship. For there to be a genetic relationship, delay discounting must have a genetic component (heritability). A review of the human and animal literature suggests that this is the case. Other literature examining whether discounting is a correlated phenotype in individuals who are genetically predisposed to drink (family history positive individuals and selected lines of rats and mice) is mixed, suggesting that networks of genes are critical for the relationship to be seen. The identities of the genes in this network are not yet known, but research examining polymorphisms associated with differences in discounting is beginning to address this issue.
Collapse
Affiliation(s)
- Suzanne H Mitchell
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, United States.
| |
Collapse
|
40
|
Madden GJ, Francisco MT, Brewer AT, Stein JS. Delay discounting and gambling. Behav Processes 2011; 87:43-9. [PMID: 21352902 DOI: 10.1016/j.beproc.2011.01.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 01/28/2011] [Accepted: 01/31/2011] [Indexed: 10/18/2022]
Abstract
Delay discounting describes the decline in the value of a reinforcer as the delay to that reinforcer increases. A review of the available studies revealed that steep delay discounting is positively correlated with problem or pathological gambling. One hypothesis regarding this correlation derives from the discounting equation proposed by Mazur (1989). According to the equation, steeper discounting renders the difference between fixed-delayed rewards and gambling-like variable-delayed rewards larger; with the latter being more valuable. The present study was designed to test this prediction by first assessing rats' impulsive choices across four delays to a larger-later reinforcer. A second condition quantified strength of preference for mixed- over fixed-delays, with the duration of the latter adjusted between sessions to achieve indifference. Strength of preference for the mixed-delay alternative is given by the fixed delay at indifference (lower fixed-delay values reflect stronger preferences). Percent impulsive choice was not correlated with the value of the fixed delay at indifference and, therefore, the prediction of the hyperbolic model of gambling was not supported. A follow-up assessment revealed a significant decrease in impulsive choice after the second condition. This shift in impulsive choice could underlie the failure to observe the predicted correlation between impulsive choice and degree of preference for mixed- over fixed delays.
Collapse
|
41
|
Beckmann JS, Marusich JA, Gipson CD, Bardo MT. Novelty seeking, incentive salience and acquisition of cocaine self-administration in the rat. Behav Brain Res 2010; 216:159-65. [PMID: 20655954 DOI: 10.1016/j.bbr.2010.07.022] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 07/16/2010] [Accepted: 07/19/2010] [Indexed: 11/19/2022]
Abstract
It has been suggested that incentive salience plays a major role in drug abuse and the development of addiction. Additionally, novelty seeking has been identified as a significant risk factor for drug abuse. However, how differences in the readiness to attribute incentive salience relate to novelty seeking and drug abuse vulnerability has not been explored. The present experiments examined how individual differences in incentive salience attribution relate to novelty seeking and acquisition of cocaine self-administration in a preclinical model. Rats were first assessed in an inescapable novelty task and a novelty place preference task (measures of novelty seeking), followed by a Pavlovian conditioned approach task for food (a measure of incentive salience attribution). Rats then were trained to self-administer cocaine (0.3 or 1.0 mg/kg/infusion) using an autoshaping procedure. The results demonstrate that animals that attributed incentive salience to a food-associated cue were higher novelty seekers and acquired cocaine self-administration more quickly at the lower dose. The results suggest that novelty-seeking behavior may be a mediator of incentive salience attribution and that incentive salience magnitude may be an indicator of drug reward.
Collapse
Affiliation(s)
- Joshua S Beckmann
- University of Kentucky, Department of Psychology, 741 S. Limestone, BBSRB, Room 447, Lexington, KY 40536-0509, United States.
| | | | | | | |
Collapse
|
42
|
Galtress T, Kirkpatrick K. The role of the nucleus accumbens core in impulsive choice, timing, and reward processing. Behav Neurosci 2010; 124:26-43. [PMID: 20141278 DOI: 10.1037/a0018464] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The present series of experiments aimed to pinpoint the source of nucleus accumbens core (AcbC) effects on delay discounting. Rats were trained with an impulsive choice procedure between an adjusting smaller sooner reward and a fixed larger later reward. The AcbC-lesioned rats produced appropriate choice behavior when the reward magnitude was equal. An increase in reward magnitude resulted in a failure to increase preference for the larger later reward in the AcbC-lesioned rats, whereas a decrease in the larger later reward duration resulted in normal alterations in choice behavior in AcbC-lesioned rats. Subsequent experiments with a peak timing (Experiments 2 and 3) and a behavioral contrast (Experiment 4) indicated that the AcbC-lesioned rats suffered from decreased incentive motivation during changes in reward magnitude (Experiments 2 and 4) and when expected rewards were omitted (Experiments 2 and 3), but displayed intact anticipatory timing of reward delays (Experiments 2 and 3). The results indicate that the nucleus accumbens core is critical for determining the incentive value of rewards, but does not participate in the timing of reward delays.
Collapse
|
43
|
Portelli J, Aourz N, De Bundel D, Meurs A, Smolders I, Michotte Y, Clinckers R. Intrastrain differences in seizure susceptibility, pharmacological response and basal neurochemistry of Wistar rats. Epilepsy Res 2009; 87:234-46. [PMID: 19833479 DOI: 10.1016/j.eplepsyres.2009.09.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 09/16/2009] [Accepted: 09/18/2009] [Indexed: 10/20/2022]
Abstract
Reliable well-characterised animal models of seizures are necessary in order to better understand the underlying pathophysiological mechanisms as well as to screen potential anticonvulsant drugs. We currently use the focal pilocarpine model as an acute limbic seizure model. Due to breeding problems at the vendor, and apparent changes in pilocarpine-induced seizure susceptibility, we were forced to change breeding locations and vendors over a period of 2 years. Male Wistar rats were either purchased from two breeding locations of Charles River Laboratories (France and Germany), or obtained from Harlan Laboratories (The Netherlands). In the present retrospective study we evaluated the impact of these vendor changes on ketamine dosing to establish anaesthesia, on pilocarpine-induced seizure susceptibility, and on basal extracellular hippocampal noradrenaline, dopamine, serotonin, gamma-amino butyric acid, and glutamate levels of all pilocarpine-treated rats included in our studies. Significant differences were present in all of the parameters analyzed. This study clearly illustrates that intrastrain differences do exist from one vendor/breeding location to another, or even between rats from the same breeding location.
Collapse
Affiliation(s)
- Jeanelle Portelli
- Department of Pharmaceutical Chemistry, Drug Analysis & Drug Information, Vrije Universiteit Brussel, Brussels, Belgium
| | | | | | | | | | | | | |
Collapse
|
44
|
Effects of variable training, signaled and unsignaled delays, and d-amphetamine on delay-discounting functions. Behav Pharmacol 2009; 20:424-36. [DOI: 10.1097/fbp.0b013e3283305ef9] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|