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Sved AF, Caggiula AR, Donny EC. Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri. Psychopharmacology (Berl) 2023; 240:417-430. [PMID: 36329195 PMCID: PMC11188050 DOI: 10.1007/s00213-022-06266-7] [Citation(s) in RCA: 2] [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: 08/31/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.
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Affiliation(s)
- Alan F Sved
- Departments of Neuroscience, Psychiatry and Psychology and the Center for Neuroscience, University of Pittsburgh, 210 Langley Hall, Pittsburgh, PA, 15260, USA.
| | - Anthony R Caggiula
- Departments of Psychology and Psychiatry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Eric C Donny
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA
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Maddux JM, Gonzales L, Kregar NP. β2* nicotinic acetylcholine receptor subtypes mediate nicotine-induced enhancement of Pavlovian conditioned responding to an alcohol cue. Front Behav Neurosci 2022; 16:1004368. [PMCID: PMC9596985 DOI: 10.3389/fnbeh.2022.1004368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/21/2022] [Indexed: 11/13/2022] Open
Abstract
Nicotine enhances Pavlovian conditioned responses to reward-associated cues. We investigated through which nicotinic acetylcholine receptor (nAChR) subtypes nicotine acts to produce this behavioral effect to an alcohol-associated cue. Male Long-Evans rats with freely available food and water were first accustomed to drinking 15% ethanol in their home cages using an intermittent access, two-bottle choice procedure. Then the rats were given 15 Pavlovian conditioning sessions in which a 15-s audiovisual conditioned stimulus (CS) predicted the delivery of 0.2 ml of ethanol, the unconditioned stimulus (US). Each session contained 12 CS-US trials. A control group received explicitly unpaired presentations of the CS and US. We measured Pavlovian conditioned approach to the site of US delivery during presentations of the CS, accounting for pre-CS baseline activity. Before each conditioning session, rats were injected subcutaneously with nicotine (0.4 mg/kg) or saline (1 ml/kg). During nAChR antagonist test sessions, rats were first injected systemically with the β2*-selective nAChR antagonist dihydro-beta-erythroidine (DHβE; 3 mg/kg) or the α7-selective nAChR antagonist methyllycaconitine (MLA; 6 mg/kg), followed by their assigned nicotine or saline injection before assessing their conditioned response to the alcohol-associated cue. Consistent with previous reports, nicotine enhanced the Pavlovian conditioned response to the alcohol-paired cue. DHβE attenuated this enhancement, whereas MLA did not. These results suggest that nicotine acts via β2*, but not α7, nAChRs to amplify Pavlovian conditioned responding to an alcohol cue. These findings contribute to a growing literature that identifies nAChRs as potential targets for pharmacological treatment of co-morbid alcohol and tobacco use disorders.
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Affiliation(s)
- Jean-Marie Maddux
- Department of Psychology, Lake Forest College, Lake Forest, IL, United States
- Neuroscience Program, Lake Forest College, Lake Forest, IL, United States
- *Correspondence: Jean-Marie Maddux
| | - Leslie Gonzales
- Department of Psychology, Lake Forest College, Lake Forest, IL, United States
- Neuroscience Program, Lake Forest College, Lake Forest, IL, United States
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King CP, Meyer PJ. The incentive amplifying effects of nicotine: Roles in alcohol seeking and consumption. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2022; 93:171-218. [PMID: 35341566 DOI: 10.1016/bs.apha.2021.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Nicotine has a unique profile among drugs of abuse. To the noninitiated user, nicotine has powerful aversive effects and its relatively weak euphorigenic effects undergo rapid tolerance. Despite this, nicotine is commonly abused despite negative heath consequences, and nicotine users have enormous difficulty quitting. Further, nicotine is one of the most commonly co-abused substances, in that it is often taken in combination with other drugs. One explanation of this polydrug use is that nicotine has multiple appetitive and consummatory conditioning effects. For example, nicotine is a reinforcement enhancer in that it can potently increase the incentive value of other stimuli, including those surrounding drugs of abuse such as alcohol. In addition, nicotine also has a unique profile of neurobiological effects that alter regulation of alcohol intake and interoception. This review discusses the psychological and biological mechanisms surrounding nicotine's appetitive conditioning and consummatory effects, particularly its interactions with alcohol.
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Affiliation(s)
- Christopher P King
- Department of Psychology, State University of New York at Buffalo, Buffalo, NY, United States; Clinical and Research Institute on Addictions, State University of New York at Buffalo, Buffalo, NY, United States
| | - Paul J Meyer
- Department of Psychology, State University of New York at Buffalo, Buffalo, NY, United States.
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Honeycutt SC, Paladino MS, Camadine RD, Mukherjee A, Loney GC. Acute nicotine treatment enhances compulsive-like remifentanil self-administration that persists despite contextual punishment. Addict Biol 2022; 27:e13170. [PMID: 35470562 PMCID: PMC9175303 DOI: 10.1111/adb.13170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/31/2022] [Accepted: 03/08/2022] [Indexed: 11/29/2022]
Abstract
Opioid use disorder (OUD) and opioid-related deaths remain a significant public health crisis having reached epidemic status globally. OUDs are defined as chronic, relapsing conditions often characterized by compulsive drug seeking despite the deleterious consequences of drug taking. The use of nicotine-containing products has been linked to increased likelihood of prescription opioid misuse, and there exists a significant comorbidity between habitual nicotine use and opioid dependence. In rodent models, nicotine administration nearly doubles the amount of opioids taken in intravenous self-administration paradigms. Here, we examined the effect of acute systemic nicotine administration in male rats on responding for the synthetic opioid remifentanil (RMF) in a contextual punishment paradigm using either an exteroceptive punisher (foot-shock) or an interoceptive punisher (histamine). Nicotine administration, relative to saline, increased RMF intake in both unpunished and punished contexts, regardless of form of punishment, and resulted in significantly higher motivation to obtain RMF in the previously punished context, as measured by progressive ratio breakpoint. Additionally, regardless of context, nicotine-treated rats were slower to extinguish RMF responding following drug removal and displayed higher levels of cue-induced reinstatement than saline-treated controls. Furthermore, these data support that, compared with histamine adulteration, contingent foot-shock is a more potent form of punishment, as histamine punishment failed to support contextual discrimination between the unpunished and punished contexts. In contrast to RMF administration, augmentation of responding for an audiovisual cue by nicotine pretreatment was lost following contextual punishment. In conclusion, acute nicotine administration in adult male rats significantly enhances compulsive-like responding for RMF that persists despite contingent punishment of drug-directed responding.
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Affiliation(s)
- Sarah C. Honeycutt
- Program in Behavioral Neuroscience, Department of Psychology State University of New York, University at Buffalo Buffalo New York USA
| | - Morgan S. Paladino
- Program in Behavioral Neuroscience, Department of Psychology State University of New York, University at Buffalo Buffalo New York USA
| | - Rece D. Camadine
- Program in Behavioral Neuroscience, Department of Psychology State University of New York, University at Buffalo Buffalo New York USA
| | - Ashmita Mukherjee
- Program in Behavioral Neuroscience, Department of Psychology State University of New York, University at Buffalo Buffalo New York USA
| | - Gregory C. Loney
- Program in Behavioral Neuroscience, Department of Psychology State University of New York, University at Buffalo Buffalo New York 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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Systemic nicotine enhances opioid self-administration and modulates the formation of opioid-associated memories partly through actions within the insular cortex. Sci Rep 2021; 11:3321. [PMID: 33558613 PMCID: PMC7870813 DOI: 10.1038/s41598-021-81955-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 01/13/2021] [Indexed: 11/24/2022] Open
Abstract
Habitual use of nicotine containing products increases propensity to misuse prescription opioids and its prevalence is substantially increased in individuals currently involved in opioid-treatment programs. Nicotine enhances self-administration of many classes of drugs in rodents, though evidence for direct effects on opioids is lacking. We sought to measure the effects of nicotine pretreatment on the reinforcing efficacy of opioids in both self-administration and contextual conditioning paradigms. First, we measured the effect of systemic nicotine pretreatment on self-administration of two opioids. Additionally, we measured the degree to which systemic nicotine pretreatment impacts the formation of morphine-associated contextual memories in conditioned taste avoidance and place preference paradigms. Given the involvement of the insula in the maintenance of substance abuse, its importance in nicotine addiction, and findings that insular inactivation impairs contextual drug conditioning, we examined whether nicotine administered directly to the insula could recapitulate the effects of systemic nicotine. We demonstrate that systemic nicotine pretreatment significantly enhances opioid self-administration and alters contextual conditioning. Furthermore, intra-insula nicotine similarly altered morphine contextual conditioning by blocking the formation of taste avoidance at all three morphine doses tested (5.0, 10, and 20 mg/kg), while shifting the dose–response curve of morphine in the place preference paradigm rightward. In conclusion, these data demonstrate that nicotine facilitates opioid intake and is partly acting within the insular cortex to obfuscate aversive opiate memories while potentiating approach to morphine-associated stimuli at higher doses.
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Nicotine Pretreatment Increases Sensitivity to Reward Devaluation in Extinction. PSYCHOLOGICAL RECORD 2020. [DOI: 10.1007/s40732-020-00422-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Vena AA, Zandy SL, Cofresí RU, Gonzales RA. Behavioral, neurobiological, and neurochemical mechanisms of ethanol self-administration: A translational review. Pharmacol Ther 2020; 212:107573. [PMID: 32437827 PMCID: PMC7580704 DOI: 10.1016/j.pharmthera.2020.107573] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2020] [Indexed: 12/16/2022]
Abstract
Alcohol use disorder has multiple characteristics including excessive ethanol consumption, impaired control over drinking behaviors, craving and withdrawal symptoms, compulsive seeking behaviors, and is considered a chronic condition. Relapse is common. Determining the neurobiological targets of ethanol and the adaptations induced by chronic ethanol exposure is critical to understanding the clinical manifestation of alcohol use disorders, the mechanisms underlying the various features of the disorder, and for informing medication development. In the present review, we discuss ethanol's interactions with a variety of neurotransmitter systems, summarizing findings from preclinical and translational studies to highlight recent progress in the field. We then describe animal models of ethanol self-administration, emphasizing the value, limitations, and validity of commonly used models. Lastly, we summarize the behavioral changes induced by chronic ethanol self-administration, with an emphasis on cue-elicited behavior, the role of ethanol-related memories, and the emergence of habitual ethanol seeking behavior.
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Affiliation(s)
- Ashley A Vena
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, United States of America
| | | | - Roberto U Cofresí
- Psychological Sciences, University of Missouri, United States of America
| | - Rueben A Gonzales
- Division of Pharmacology and Toxicology, College of Pharmacy and Institute for Neuroscience, The University of Texas at Austin, United States of America.
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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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Loney GC, Pautassi RM, Kapadia D, Meyer PJ. Nicotine affects ethanol-conditioned taste, but not place, aversion in a simultaneous conditioning procedure. Alcohol 2018; 71:47-55. [PMID: 30029019 DOI: 10.1016/j.alcohol.2018.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/21/2018] [Accepted: 02/26/2018] [Indexed: 12/20/2022]
Abstract
The conditioned taste aversion (CTA) induced by ethanol is a key factor limiting ethanol intake. Nicotine, a drug co-consumed with ethanol, may decrease this aversion by modulating the unconditioned effects of ethanol or by disrupting the association between ethanol and its associated cues. This study analyzed ethanol-induced CTA and conditioned place aversion (CPA) in Long-Evans rats with subchronic exposure to nicotine. The rats were treated with nicotine (0.0 or 0.4 mg/kg) three times before conditioning (on lickometer training sessions 3, 4, and 5) and across conditioning days. During the conditioning the rats were given ethanol (1.3 g/kg) preceded and followed by presentation of a taste (NaCl) and tactile (rod or hole floors) conditioned stimulus (CS+), respectively. On CS- conditioning days, the rats were given vehicle and exposed to alternative stimuli. Three CTA and CPA testing sessions were then conducted. It was found that nicotine reduced ethanol-induced CTA and enhanced locomotor activity, but did not significantly modify the magnitude of ethanol-induced CPA. The effects of nicotine on CTA were observed during both conditioning and testing sessions, and were specific to the NaCl CS+, having no effect on reactivity to water. The dissociation between the effect of nicotine on ethanol-induced CTA and CPA suggests that nicotine does not alter ethanol's motivational properties by generally increasing its positive rewarding effects, nor does it blunt all aversive-like responses to this drug. Instead, nicotine may impede ethanol-induced CTA induced by ethanol by disrupting the neural underpinnings of this specific form of associative learning.
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Affiliation(s)
- Gregory C Loney
- Department of Psychology, State University of New York at Buffalo, Buffalo, NY 14260, United States
| | - Ricardo Marcos Pautassi
- Instituto de Investigación Médica M. y M. Ferreyra (INIMEC - CONICET-UNC), Córdoba, C.P. 5000, Argentina; Facultad de Psicología, Universidad Nacional de Córdoba, Córdoba, C.P. 5000, Argentina.
| | | | - Paul J Meyer
- Department of Psychology, State University of New York at Buffalo, Buffalo, NY 14260, United States
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Ostroumov A, Dani JA. Convergent Neuronal Plasticity and Metaplasticity Mechanisms of Stress, Nicotine, and Alcohol. Annu Rev Pharmacol Toxicol 2017; 58:547-566. [PMID: 28977763 DOI: 10.1146/annurev-pharmtox-010617-052735] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Stress and tobacco smoking are risk factors for alcoholism, but the underlying neural mechanisms are not well understood. Although stress, nicotine, and alcohol have broad, individual effects in the brain, some of their actions converge onto the same mechanisms and circuits. Stress and nicotine augment alcohol-related behaviors, in part via modulation of alcohol-evoked neuronal plasticity and metaplasticity mechanisms. Stress modulates alcohol-evoked plasticity via the release of signaling molecules that influence synaptic transmission. Nicotine also activates some of the same signaling molecules, cells, and circuits, producing a convergence of both stress and nicotine onto common plasticity mechanisms that influence alcohol self-administration. We describe several forms of alcohol-induced plasticity, including classic Hebbian plasticity at glutamatergic synapses, and we highlight less appreciated forms, such as non-Hebbian and GABAergic synaptic plasticity. Risk factors such as stress and nicotine initiate lasting neural changes that modify subsequent alcohol-induced synaptic plasticity and increase the vulnerability to alcohol addiction.
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Affiliation(s)
- Alexey Ostroumov
- Department of Neuroscience, Mahoney Institute for Neurosciences, Perelman School for Medicine, Philadelphia, Pennsylvania 19104, USA; ,
| | - John A Dani
- Department of Neuroscience, Mahoney Institute for Neurosciences, Perelman School for Medicine, Philadelphia, Pennsylvania 19104, USA; ,
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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: 4] [Impact Index Per Article: 0.6] [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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