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Pochapski JA, Gómez-A A, Stringfield SJ, Jaggers H, Boettiger CA, Da Cunha C, Robinson DL. Adolescent alcohol exposure persistently alters orbitofrontal cortical encoding of Pavlovian conditional stimulus components in female rats. Sci Rep 2024; 14:13775. [PMID: 38877100 PMCID: PMC11178901 DOI: 10.1038/s41598-024-64036-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 06/04/2024] [Indexed: 06/16/2024] Open
Abstract
Exposure to alcohol during adolescence impacts cortical and limbic brain regions undergoing maturation. In rodent models, long-term effects on behavior and neurophysiology have been described after adolescent intermittent ethanol (AIE), especially in males. We hypothesized that AIE in female rats increases conditional approach to a reward-predictive cue and corresponding neuronal activity in the orbitofrontal cortex (OFC) and nucleus accumbens (NAc). We evaluated behavior and neuronal firing after AIE (5 g/kg intragastric) or water (CON) in adult female rats. Both AIE and CON groups expressed a ST phenotype, and AIE marginally increased sign-tracking (ST) and decreased goal-tracking (GT) metrics. NAc neurons exhibited phasic firing patterns to the conditional stimulus (CS), with no differences between groups. In contrast, neuronal firing in the OFC of AIE animals was greater at CS onset and offset than in CON animals. During reward omission, OFC responses to CS offset normalized to CON levels, but enhanced OFC firing to CS onset persisted in AIE. We suggest that the enhanced OFC neural activity observed in AIE rats to the CS could contribute to behavioral inflexibility. Ultimately, AIE persistently impacts the neurocircuitry of reward-motivated behavior in female rats.
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Affiliation(s)
- Jose A Pochapski
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, PR, Brazil
| | - Alexander Gómez-A
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | | | - Hannah Jaggers
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Charlotte A Boettiger
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- Department of Psychology and Neuroscience, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Claudio Da Cunha
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, PR, Brazil
- Department of Biochemistry, Universidade Federal do Parana, Curitiba, PR, Brazil
| | - Donita L Robinson
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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Angelyn H, Loney GC, Meyer PJ. Nicotine Enhances Goal-Tracking in Ethanol and Food Pavlovian Conditioned Approach Paradigms. Front Neurosci 2021; 15:561766. [PMID: 34483813 PMCID: PMC8416423 DOI: 10.3389/fnins.2021.561766] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/20/2021] [Indexed: 11/13/2022] Open
Abstract
Rationale Nicotine promotes alcohol intake through pharmacological and behavioral interactions. As an example of the latter, nicotine can facilitate approach toward food- and alcohol-associated stimuli ("sign-tracking") in lever-Pavlovian conditioned approach (PavCA) paradigms. However, we recently reported that nicotine can also enhance approach toward locations of reward delivery ("goal-tracking") triggered by ethanol-predictive stimuli when the location of ethanol delivery is non-static (i.e., a retractable sipper bottle). Objective To determine whether the non-static nature of the reward location could have biased the development of goal-tracking in our previous study (Loney et al., 2019); we assessed the effect of nicotine in a lever-PavCA paradigm wherein the location of ethanol delivery was static (i.e., a stationary liquid receptacle). Then, to determine whether nicotine's enhancement of goal-tracking is unique to ethanol-predictive stimuli, we assessed the effect of systemic nicotine on approach triggered by food-predictive stimuli in a lever-PavCA paradigm. Methods Long-Evans rats were used in two PavCA experiments wherein a lever predicted the receipt of ethanol (15% vol/vol; experiment 1) or food (experiment 2) into a stationary receptacle. Prior to testing, rats were administered nicotine (0.4 mg/kg subcutaneously) or saline systemically. Results In both experiments, nicotine increased measures of goal-tracking, but not sign-tracking. Conclusion Nicotine can facilitate approach to reward locations without facilitating approach to reward-predictive stimuli. As such, conceptualization of the mechanisms by which nicotine affects behavior must be expanded to explain an enhancement of goal-tracking by nicotine.
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Affiliation(s)
- Hailley Angelyn
- Behavioral Neuroscience Program, Department of Psychology, State University of New York at Buffalo, Buffalo, NY, United States
| | - Gregory C Loney
- Behavioral Neuroscience Program, Department of Psychology, State University of New York at Buffalo, Buffalo, NY, United States
| | - Paul J Meyer
- Behavioral Neuroscience Program, Department of Psychology, State University of New York at Buffalo, Buffalo, NY, United States
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3
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Abstract
Learning to respond appropriately to one's surrounding environment is fundamental to survival. Importantly, however, individuals vary in how they respond to cues in the environment and this variation may be a key determinant of psychopathology. The ability of seemingly neutral cues to promote maladaptive behavior is a hallmark of several psychiatric disorders including, substance use disorder, post-traumatic stress disorder, eating disorders and obsessive-compulsive disorder. Thus, it is important to uncover the neural mechanisms by which such cues are able to attain inordinate control and promote psychopathological behavior. Here, we suggest that glucocorticoids play a critical role in this process. Glucocorticoids are primarily recognized as the main hormone secreted in response to stress but are known to exert their effects across the body and the brain, and to affect learning and memory, cognition and reward-related behaviors, among other things. Here we speculate that glucocorticoids act to facilitate a dopamine-dependent form of cue-reward learning that appears to be relevant to a number of psychiatric conditions. Specifically, we propose to utilize the sign-tracker/goal-tracker animal model as a means to capture individual variation in stimulus-reward learning and to isolate the role of glucocorticoid-dopamine interactions in mediating these individual differences. It is hoped that this framework will lead to the discovery of novel mechanisms that contribute to complex neuropsychiatric disorders and their comorbidity.
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Affiliation(s)
- Sofia A. Lopez
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Shelly B. Flagel
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
- Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
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Robinson MJ, Clibanoff C, Freeland CM, Knes AS, Cote JR, Russell TI. Distinguishing between predictive and incentive value of uncertain gambling-like cues in a Pavlovian autoshaping task. Behav Brain Res 2019; 371:111971. [DOI: 10.1016/j.bbr.2019.111971] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/17/2019] [Accepted: 05/21/2019] [Indexed: 01/22/2023]
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Stringfield SJ, Madayag AC, Boettiger CA, Robinson DL. Sex differences in nicotine-enhanced Pavlovian conditioned approach in rats. Biol Sex Differ 2019; 10:37. [PMID: 31315660 PMCID: PMC6637589 DOI: 10.1186/s13293-019-0244-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 05/28/2019] [Indexed: 01/01/2023] Open
Abstract
Background Nicotine exposure enhances Pavlovian conditioned approach (PCA), or the learned approach to reward-predictive cues. While females show elevated approach to conditioned stimuli compared to males, potentially indicating heightened addiction vulnerability, it is unknown how sex may interact with nicotine to influence approach behavior. Additionally, brain-derived neurotrophic factor (BDNF) levels can be altered significantly after repeated nicotine exposure, suggesting a potential mechanism contributing to nicotine-induced behavioral phenotypes. The present study investigated the role of sex on nicotine-induced changes to stimulus-response behavior and associated BDNF protein levels. Methods Male and female rats were exposed to nicotine (0.4 mg/kg, subcutaneously) or saline 15 min prior to each PCA session. PCA training consisted of 29 sessions of 15 trials, in which a 30-s cue presentation ended concurrently with a sucrose reward (20% w/v in water, 100 μL), and a 120-s variable intertrial interval occurred between trials. Approach behavior to the cue and reward receptacle was recorded. Preference toward the reward receptacle indicated a goal-tracking phenotype, and preference toward the cue indicated a sign-tracking phenotype, demonstrating that the cue had gained incentive salience. Twenty-four hours after the last PCA session, brain tissue was collected and BDNF levels were measured in the basolateral amygdala, orbitofrontal cortex, and nucleus accumbens using Western blot analysis. Results Nicotine exposure enhanced both sign- and goal-tracking conditioned approach, and females showed elevated sign-tracking compared to males. There were no sex-by-drug interactions on conditioned approach. Day-to-day variability in conditioned approach was similar between sexes. In contrast to prior studies, neither repeated exposure to nicotine nor sex significantly affected BDNF expression. Conclusions Drug-naïve females exhibited heightened sign-tracking compared to males, and nicotine enhanced conditioned approach similarly in males and females. Further, non-significant changes to BDNF expression in brain regions highly associated with PCA indicate that BDNF is unlikely to drive nicotine-enhanced conditioned behavior.
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Affiliation(s)
- Sierra J Stringfield
- Bowles Center for Alcohol Studies, University of North Carolina, CB #7178, Chapel Hill, NC, 27599-7178, USA.,Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA
| | - Aric C Madayag
- Bowles Center for Alcohol Studies, University of North Carolina, CB #7178, Chapel Hill, NC, 27599-7178, USA
| | - Charlotte A Boettiger
- Bowles Center for Alcohol Studies, University of North Carolina, CB #7178, Chapel Hill, NC, 27599-7178, USA.,Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA.,Department of Psychology and Neuroscience, University of North Carolina, Chapel Hill, NC, USA
| | - Donita L Robinson
- Bowles Center for Alcohol Studies, University of North Carolina, CB #7178, Chapel Hill, NC, 27599-7178, USA. .,Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA. .,Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA.
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Loney GC, Angelyn H, Cleary LM, Meyer PJ. Nicotine Produces a High-Approach, Low-Avoidance Phenotype in Response to Alcohol-Associated Cues in Male Rats. Alcohol Clin Exp Res 2019; 43:1284-1295. [PMID: 30958564 DOI: 10.1111/acer.14043] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 04/01/2019] [Indexed: 11/28/2022]
Abstract
BACKGROUND Nicotine and alcohol use are highly comorbid. Modulation of drug-paired extrinsic and intrinsic cues likely plays a role in this interaction, as cues can acquire motivational properties and augment drug seeking. The motivational properties of cues can be measured through Pavlovian conditioning paradigms, in which cues either elicit approach following pairing with the reinforcing properties of alcohol or elicit avoidance following pairing with the aversive consequences of alcohol. The present experiments tested whether nicotine would enhance the incentive properties of an appetitive ethanol (EtOH) cue and diminish the avoidance of an aversive EtOH cue in Pavlovian paradigms. METHODS In experiment 1, male Long-Evans rats with or without prior chronic intermittent access to EtOH were administered nicotine or saline injections prior to Pavlovian conditioned approach (PavCA) sessions, during which conditioned approach to the cue ("sign-tracking") or the EtOH delivery location ("goal-tracking") was measured. In experiment 2, male Long-Evans rats were administered nicotine or saline injections prior to pairing a flavor cue with increasing doses of EtOH (i.p.) in an adaptation of the conditioned taste avoidance (CTA) paradigm. RESULTS Results from PavCA indicate that, regardless of EtOH exposure, nicotine enhanced responding elicited by EtOH-paired cues with no effect on a similar cue not explicitly paired with EtOH. Furthermore, nicotine reduced sensitivity to EtOH-induced CTA, as indicated by a rightward shift in the dose-response curve of passively administered EtOH. The ED50 , or the dose of EtOH that produced a 50% reduction in intake relative to baseline, was significantly higher in nicotine-treated rats compared to saline-treated rats. CONCLUSIONS We conclude that nicotine increases the approach and diminishes the avoidance elicited by Pavlovian cues paired, respectively, with the reinforcing and aversive properties of EtOH consumption in male rats. As such, nicotine may enhance alcoholism liability by engendering an attentional bias toward cues that predict the reinforcing outcomes of drinking.
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Affiliation(s)
- Gregory C Loney
- Department of Psychology, Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York
| | - Hailley Angelyn
- Department of Psychology, Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York
| | - Liam M Cleary
- Department of Psychology, Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York
| | - Paul J Meyer
- Department of Psychology, Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York
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Overby PF, Daniels CW, Del Franco A, Goenaga J, Powell GL, Gipson CD, Sanabria F. Effects of nicotine self-administration on incentive salience in male Sprague Dawley rats. Psychopharmacology (Berl) 2018; 235:1121-1130. [PMID: 29374305 DOI: 10.1007/s00213-018-4829-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Accepted: 01/03/2018] [Indexed: 12/26/2022]
Abstract
RATIONALE Prolonged use of nicotine appears to enhance incentive salience, a motivational-cognitive process that transforms an otherwise neutral stimulus into a "wanted" stimulus. It has been suggested that nicotinic enhancement of incentive salience contributes to the potential of relapse in individuals with tobacco addiction. However, there are two main limitations of prior research that caution this claim: (a) the use of passive experimentally delivered nicotine and (b) the use of sign-tracking as an index of incentive salience, without acknowledging the competing nature of goal- and sign-tracking responses. OBJECTIVES To determine whether nicotinic enhancement of incentive salience attributed to non-nicotinic stimuli occurs when rats self-administer nicotine, and whether it is facilitated by a prior history of nicotine self-administration. METHODS Twenty-three male rats were trained daily, for 24 days, on a nicotine self-administration (SA) paradigm in the morning, and on a four-conditioned-stimuli Pavlovian conditioned approach (4-CS PCA) task in the afternoon. Self-administration was followed by extinction and cue reinstatement. A subcutaneous nicotine challenge was performed during the last 7 days of the study. RESULTS Nicotine self-administration selectively enhanced sign-tracking in the 4-CS PCA. Upon extinction, sign-tracking quickly declined to control levels. Experimenter-administered nicotine enhanced sign-tracking similarly regardless of nicotine history. CONCLUSIONS The results suggest that nicotinic enhancement of incentive salience is transient, and a previous history of nicotine use does not cause further sensitization. Taken together, these results suggest that nicotine enhances incentive salience, particularly-and perhaps exclusively-while onboard.
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Affiliation(s)
- Paula F Overby
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Carter W Daniels
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Armani Del Franco
- School of Life Sciences, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Julianna Goenaga
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Gregory L Powell
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
- School of Life Sciences, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Cassandra D Gipson
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA
| | - Federico Sanabria
- Department of Psychology, Arizona State University, P.O. Box 871104, Tempe, AZ, 85287-1104, USA.
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8
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Stringfield SJ, Boettiger CA, Robinson DL. Nicotine-enhanced Pavlovian conditioned approach is resistant to omission of expected outcome. Behav Brain Res 2018; 343:16-20. [PMID: 29407412 DOI: 10.1016/j.bbr.2018.01.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 01/18/2018] [Accepted: 01/19/2018] [Indexed: 11/30/2022]
Abstract
Conditioned stimuli contribute to the resilience of nicotine addiction in that nicotine-associated cues can influence smokers and promote relapse. These stimuli are thought to acquire incentive motivational properties through a Pavlovian mechanism, and this phenomenon can be measured in animals by observing conditioned approach to the conditioned stimulus (sign-tracking) or to the location of unconditioned stimulus delivery (goal-tracking). Goal-tracking is thought to be more flexible than sign-tracking in response to changes in expected outcome. Nicotine exposure can increase the expression of conditioned responses, and we hypothesized that animals exposed to nicotine would also exhibit less flexible conditioned responses after a change in the expected unconditioned stimulus. Adult male rats were exposed to nicotine (0.4mg/kg, s.c.) or saline before Pavlovian conditioned approach training sessions. After training, animals underwent test sessions that reduced (water substitution) or withheld (omission) the unconditioned stimulus (US, 20% sucrose). As expected, nicotine enhanced sign- and goal-tracking. Water substitution moderately and nonspecifically reduced both sign- and goal-tracking in all rats. In contrast, US omission only reduced goal-tracking, with robust effects in saline-exposed rats and smaller effects in nicotine-exposed rats. These data support the hypothesis that both sign-tracking and nicotine exposure confer behavioral inflexibility under US omission.
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Affiliation(s)
- Sierra J Stringfield
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, USA; Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA
| | - Charlotte A Boettiger
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, USA; Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA; Department of Psychology and Neuroscience, University of North Carolina, Chapel Hill, NC, USA
| | - Donita L Robinson
- Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, USA; Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC, USA; Department of Psychiatry, University of North Carolina, Chapel Hill, NC, USA.
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9
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Nasser HM, Lafferty DS, Lesser EN, Bacharach SZ, Calu DJ. Disconnection of basolateral amygdala and insular cortex disrupts conditioned approach in Pavlovian lever autoshaping. Neurobiol Learn Mem 2018; 147:35-45. [PMID: 29169849 PMCID: PMC5972554 DOI: 10.1016/j.nlm.2017.11.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/20/2017] [Accepted: 11/18/2017] [Indexed: 01/09/2023]
Abstract
Previously established individual differences in appetitive approach and devaluation sensitivity observed in goal- and sign-trackers may be attributed to differences in the acquisition, modification, or use of associative information in basolateral amygdala (BLA) pathways. Here, we sought to determine the extent to which communication of associative information between BLA and anterior portions of insular cortex (IC) supports ongoing Pavlovian conditioned approach behaviors in sign- and goal-tracking rats, in the absence of manipulations to outcome value. We hypothesized that the BLA mediates goal-, but not sign- tracking approach through interactions with the IC, a brain region involved in supporting flexible behavior. We first trained rats in Pavlovian lever autoshaping to determine their sign- or goal-tracking tendency. During alternating test sessions, we gave unilateral intracranial injections of vehicle or a cocktail of gamma-aminobutyric acid (GABA) receptor agonists, baclofen and muscimol, unilaterally into the BLA and contralaterally or ipsilaterally into the IC prior to reinforced lever autoshaping sessions. Consistent with our hypothesis we found that contralateral inactivation of BLA and IC increased the latency to approach the food cup and decreased the number of food cup contacts in goal-trackers. While contralateral inactivation of BLA and IC did not affect the total number of lever contacts in sign-trackers, this manipulation increased the latency to approach the lever. Ipsilateral inactivation of BLA and IC did not impact approach behaviors in Pavlovian lever autoshaping. These findings, contrary to our hypothesis, suggest that communication between BLA and IC maintains a representation of initially learned appetitive associations that commonly support the initiation of Pavlovian conditioned approach behavior regardless of whether it is directed at the cue or the location of reward delivery.
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Affiliation(s)
- Helen M Nasser
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Danielle S Lafferty
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Ellen N Lesser
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Sam Z Bacharach
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Donna J Calu
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, United States.
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Madayag AC, Czarnecki KS, Wangler LM, Robinson DL. Chronic Nicotine Exposure Initiated in Adolescence and Unpaired to Behavioral Context Fails to Enhance Sweetened Ethanol Seeking. Front Behav Neurosci 2017; 11:153. [PMID: 28860980 PMCID: PMC5562684 DOI: 10.3389/fnbeh.2017.00153] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 08/02/2017] [Indexed: 01/01/2023] Open
Abstract
Nicotine use in adolescence is pervasive in the United States and, according to the Gateway Hypothesis, may lead to progression towards other addictive substances. Given the prevalence of nicotine and ethanol comorbidity, it is difficult to ascertain if nicotine is a gateway drug for ethanol. Our study investigated the relationship between adolescent exposure to nicotine and whether this exposure alters subsequent alcohol seeking behavior. We hypothesized that rats exposed to nicotine beginning in adolescence would exhibit greater alcohol seeking behavior than non-exposed siblings. To test our hypothesis, beginning at P28, female rats were initially exposed to once daily nicotine (0.4 mg/kg, SC) or saline for 5 days. Following these five initial injections, animals were trained to nose-poke for sucrose reinforcement (10%, w/v), gradually increasing to sweetened ethanol (10% sucrose; 10% ethanol, w/v) on an FR5 reinforcement schedule. Nicotine injections were administered after the behavioral sessions to minimize acute effects of nicotine on operant self-administration. We measured the effects of nicotine exposure on the following aspects of ethanol seeking: self-administration, naltrexone (NTX)-induced decreases, habit-directed behavior, motivation, extinction and reinstatement. Nicotine exposure did not alter self-administration or the effectiveness of NTX to reduce alcohol seeking. Nicotine exposure blocked habit-directed ethanol seeking. Finally, nicotine did not alter extinction learning or cue-induced reinstatement to sweetened ethanol seeking. Our findings suggest that nicotine exposure outside the behavioral context does not escalate ethanol seeking. Further, the Gateway Hypothesis likely applies to scenarios in which nicotine is either self-administered or physiologically active during the behavioral session.
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Affiliation(s)
- Aric C Madayag
- Bowles Center for Alcohol Studies, University of North CarolinaChapel Hill, NC, United States.,Department of Pharmacology, University of North CarolinaChapel Hill, NC, United States
| | - Kyle S Czarnecki
- Bowles Center for Alcohol Studies, University of North CarolinaChapel Hill, NC, United States
| | - Lynde M Wangler
- Bowles Center for Alcohol Studies, University of North CarolinaChapel Hill, NC, United States
| | - Donita L Robinson
- Bowles Center for Alcohol Studies, University of North CarolinaChapel Hill, NC, United States.,Department of Psychiatry, University of North CarolinaChapel Hill, NC, United States
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