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McNealy KR, Oevermann MW, Knabel ML, Fitzwater A, Gipson CD, Barrett ST, Bevins RA. Repeated exposure to physiologically effective doses of contraceptive hormones ethinyl estradiol or levonorgestrel do not alter the reinforcing effects of a brief visual stimulus in ovary-intact rats. Horm Behav 2024; 161:105506. [PMID: 38387104 DOI: 10.1016/j.yhbeh.2024.105506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/09/2024] [Accepted: 02/14/2024] [Indexed: 02/24/2024]
Abstract
Estradiol and progesterone potentiate and attenuate reward processes, respectively. Despite these well-characterized effects, there is minimal research on the effects of synthetic estrogens (e.g., ethinyl estradiol, or EE) and progestins (e.g., levonorgestrel, or LEVO) contained in clinically-utilized hormonal contraceptives. The present study characterized the separate effects of repeated exposure to EE or LEVO on responding maintained by a reinforcing visual stimulus. Forty ovary-intact female Sprague-Dawley rats received either sesame oil vehicle (n = 16), 0.18 μg/day EE (n = 16), or 0.6 μg/day LEVO (n = 8) subcutaneous injections 30-min before daily one-hour sessions. Rats' responding was maintained by a 30-sec visual stimulus on a Variable Ratio-3 schedule of reinforcement. The day after rats' last session, we determined rats estrous cycle phase via vaginal cytology before sacrifice and subsequently weighing each rat's uterus to further verify the contraceptive hormone manipulation. The visual stimulus functioned as a reinforcer, but neither EE nor LEVO enhanced visual stimulus maintained responding. Estrous cytology was consistent with normal cycling in vehicle rats and halting of normal cycling in EE and LEVO rats. EE increased uterine weights consistent with typical uterotrophic effects observed with estrogens, further confirming the physiological impacts of our EE and LEVO doses. In conclusion, a physiologically effective dose of neither EE nor LEVO did not alter the reinforcing efficacy of a visual stimulus reinforcer. Future research should characterize the effects of hormonal contraceptives on responding maintained by other reinforcer types to determine the generality of the present findings.
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Affiliation(s)
- Kathleen R McNealy
- University of Nebraska-Lincoln, Department of Psychology, 238 Burnett Hall, Lincoln, NE 68588, USA.
| | - Matthew W Oevermann
- University of Nebraska-Lincoln, Department of Psychology, 238 Burnett Hall, Lincoln, NE 68588, USA
| | - MacKenzie L Knabel
- University of Nebraska-Lincoln, Department of Psychology, 238 Burnett Hall, Lincoln, NE 68588, USA
| | - Anna Fitzwater
- University of Nebraska-Lincoln, Institutional Animal Care Program, 2200 Vine Street, 278 Prem S. Paul Research Center at Whittier School, Lincoln, NE 68583, USA
| | - Cassandra D Gipson
- University of Kentucky, Department of Pharmacology and Nutrition Sciences, 780 Rose Street, MS305, Lexington, KY 40536, USA
| | - Scott T Barrett
- University of Nebraska-Lincoln, Department of Psychology, 238 Burnett Hall, Lincoln, NE 68588, USA
| | - Rick A Bevins
- University of Nebraska-Lincoln, Department of Psychology, 238 Burnett Hall, Lincoln, NE 68588, USA
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Robison CL, Cova N, Madore V, Allen T, Barrett S, Charntikov S. Assessment of ethanol and nicotine interactions using a reinforcer demand modeling with grouped and individual levels of analyses in a long-access self-administration model using male rats. Front Behav Neurosci 2023; 17:1291128. [PMID: 38098500 PMCID: PMC10720750 DOI: 10.3389/fnbeh.2023.1291128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 11/07/2023] [Indexed: 12/17/2023] Open
Abstract
Previous reports have indicated the reciprocal effects of nicotine and ethanol on their rewarding and reinforcing properties, but studies using methodological approaches resembling substance use in vulnerable populations are lacking. In our study, rats first self-administered ethanol, and their sensitivity to ethanol's reinforcing effects was assessed using a reinforcer demand modeling approach. Subsequently, rats were equipped with intravenous catheters to self-administer nicotine, and their sensitivity to nicotine's reinforcing effects was evaluated using the same approach. In the final phase, rats were allowed to self-administer ethanol and nicotine concurrently, investigating the influence of one substance on the rate of responding for the other substance. Group analyses revealed notable differences in demand among sucrose, sweetened ethanol, and ethanol-alone, with sucrose demonstrating the highest demand and ethanol-alone exhibiting greater sensitivity to changes in cost. At the individual level, our study finds significant correlations between rats' demand for sucrose and sweetened ethanol, suggesting parallel efforts for both substances. Our individual data also suggest interconnections in the elasticity of demand for sweetened ethanol and ethanol-alone, as well as a potential relationship in price response patterns between ethanol and nicotine. Furthermore, concurrent self-administration of ethanol and nicotine at the group level displayed reciprocal effects, with reduced responding for nicotine in the presence of ethanol and increased responding for ethanol in the presence of nicotine. This study provides valuable insights into modeling the co-use of ethanol and nicotine and assessing their interaction effects using reinforcer demand modeling and concurrent self-administration or noncontingent administration tests. These findings contribute to our understanding of the complex interplay between ethanol and nicotine and have implications for elucidating the underlying mechanisms involved in polydrug use.
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Affiliation(s)
| | - Nicole Cova
- Department of Psychology, University of New Hampshire, Durham, NH, United States
| | - Victoria Madore
- Department of Psychology, University of New Hampshire, Durham, NH, United States
| | - Tyler Allen
- Department of Psychology, University of New Hampshire, Durham, NH, United States
| | - Scott Barrett
- Department of Psychology, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Sergios Charntikov
- Department of Psychology, University of New Hampshire, Durham, NH, United States
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3
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Barrett ST, Flynn AT, Huynh YW, Bevins RA. Appetitive Pavlovian conditioning of the stimulus effects of nicotine enhances later nicotine self-administration. J Exp Anal Behav 2022; 117:543-559. [PMID: 35192221 PMCID: PMC9090954 DOI: 10.1002/jeab.740] [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] [Received: 10/15/2021] [Revised: 12/21/2021] [Accepted: 01/10/2022] [Indexed: 11/10/2022]
Abstract
Nicotine produces robust stimulus effects that can be conditioned to exert stimulus control over behavior through associative learning. Additionally, nicotine has weak reinforcing effects that are inconsistent with its prevalence of use and the tenacity of nicotine dependence. The present study investigated whether conditioned associations to the nicotine drug stimulus may confer additional reinforcing strength to nicotine that thereby increase its use liability, and presents a new methodological approach to investigating the interaction between the stimulus effects and reinforcing effects of drugs. Male and female Sprague-Dawley rats were divided into groups receiving intravenous infusions of either 0.03 mg/kg nicotine or 0.9% saline that were either Paired (30 s delayed) or explicitly Unpaired (4 to 6 min delayed) with sucrose deliveries over 24 daily conditioning sessions. Thereafter, recessed nosepoke response devices were installed in the chambers and infusions of their assigned drug solutions were contingently available according to a progressive ratio schedule. Rats in the Paired Nicotine condition acquired the nosepoke response, expressed active nosepoke discrimination, and self-administered significantly more infusions than rats in any of the other groups. These results demonstrate that the interoceptive stimulus effects of nicotine can form Pavlovian associations with reinforcing events that alter its reinforcement efficacy.
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Affiliation(s)
| | | | - Y Wendy Huynh
- Department of Psychology, University of Nebraska, Lincoln
| | - Rick A Bevins
- Department of Psychology, University of Nebraska, Lincoln
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4
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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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McNealy KR, Houser SD, Barrett ST, Bevins RA. Investigating sex differences and the effect of drug exposure order in the sensory reward-enhancing effects of nicotine and d-amphetamine alone and in combination. Neuropharmacology 2022; 202:108845. [PMID: 34678376 PMCID: PMC8627442 DOI: 10.1016/j.neuropharm.2021.108845] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 09/30/2021] [Accepted: 10/15/2021] [Indexed: 01/03/2023]
Abstract
Nicotine enhances the rewarding effects of other environmental stimuli; this reward-enhancement encourages and maintains nicotine consumption. Nicotine use precedes other psychostimulant use, but receiving a stimulant prescription also predicts future smoking. Previously, no study has investigated effects of drug exposure order in reward-enhancement, nor with nicotine and d-amphetamine. Thus, we aimed to investigate how drug exposure order impacted the reward-enhancing effects of nicotine and d-amphetamine, alone and in combination. We used 20 male and 20 female Sprague-Dawley rats. Enhancement was investigated within-subjects by examining responding maintained by a visual stimulus reinforcer following a pre-session injection of either d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) or nicotine (Sal, 0.03, 0.06, 0.1, 0.3 mg/kg). Twenty rats (10 M, 10 F) completed enhancement testing with nicotine before d-amphetamine. The other 20 rats (10 M, 10 F) completed testing with d-amphetamine before nicotine. Following these phases, rats were then given two pre-session injections: one of d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) and another of nicotine (Sal, 0.03, 0.06, 0.1, or 0.3 mg/kg). Experiencing amphetamine before nicotine increased reward-enhancing effects of nicotine. Females exhibited greater effects of d-amphetamine on reward-enhancement, with no effect of exposure order. During the interaction phase, receiving nicotine before amphetamine enhanced the interaction between nicotine and d-amphetamine for females whereas amphetamine before nicotine heightened this interaction for males. From this, prior and current amphetamine use, in addition to sex, should be considered when treating nicotine dependency and when examining factors driving poly-substance use involving nicotine and d-amphetamine. Keywords: Adderall, ADHD, Dexedrine, operant, smoking, polysubstance use.
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Affiliation(s)
- Kathleen R McNealy
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Sydney D Houser
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Scott T Barrett
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA
| | - Rick A Bevins
- Department of Psychology University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE, 68588-0308, USA.
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6
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LeSage MG. Stimulus functions of nicotine. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2022; 93:133-170. [PMID: 35341565 PMCID: PMC9438898 DOI: 10.1016/bs.apha.2021.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Behavioral pharmacology has made vital contributions to the concepts and methods used in tobacco and other drug use research, and is largely responsible for the now generally accepted notion that nicotine is the primary component in tobacco that engenders and maintains tobacco use. One of the most important contributions of behavioral pharmacology to the science of drug use is the notion that drugs can act as environmental stimuli that control behavior in many of the same ways as other stimuli (e.g., visual, gustatory, olfactory). The purpose of this chapter is to provide an overview of research that illustrates the respondent and operant stimulus functions of nicotine, using a contemporary taxonomy of stimulus functions as a general framework. Each function is formally defined and examples from research on the behavioral pharmacology of nicotine are presented. Some of the factors that modulate each function are also discussed. The role of nicotine's stimulus functions in operant and respondent theories of tobacco use is examined and some suggestions for future research are presented. The chapter illustrates how a taxonomy of stimulus functions can guide conceptions of tobacco use and direct research and theory accordingly.
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McNealy KR, Ramsay ME, Barrett ST, Bevins RA. Reward-enhancing effects of d-amphetamine and its interactions with nicotine were greater in female rats and persisted across schedules of reinforcement. Behav Pharmacol 2021; 32:435-447. [PMID: 34010168 PMCID: PMC8266728 DOI: 10.1097/fbp.0000000000000637] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nicotine enhances the value of environmental stimuli and rewards, and reward enhancement can maintain nicotine consumption. Stimulants such as d-amphetamine are misused more by women and are commonly co-used with nicotine. d-Amphetamine potentiates nicotine's effects in human and animal research. To date, there are no published studies examining this interaction in a reward-enhancement task. The current study sought to investigate the reward-enhancing effects of nicotine alongside and coadministered with d-amphetamine. Further, we evaluated the persistence of reward enhancement across ratio and temporal schedules of reinforcement. We used 10 male and 10 female Sprague-Dawley rats. Enhancement was assessed within subjects by examining active lever pressing for a visual stimulus reinforcer on variable ratio 3, variable interval 30 s and variable time 30 s - variable ratio 3 schedules. Before 1-h sessions, rats received one injection of saline, 0.1 or 0.3 mg/kg d-amphetamine and one of saline or 0.4 mg/kg nicotine, making six possible drug combinations (saline + saline, saline + nicotine, 0.1 d-amphetamine + aline, 0.1 d-amphetamine + nicotine, 0.3 d-amphetamine + saline and 0.3 d-amphetamine + nicotine) experienced in a randomized order by each rat. When d-amphetamine was coadministered with nicotine, we found an interaction effect on reward enhancement that persisted across schedules of reinforcement. Males and females exhibited reward enhancement by 0.3 d-amphetamine, while only females showed reward enhancement by 0.1 d-amphetamine. Further, females responded more for the visual stimulus than males in all d-amphetamine conditions. Future studies should assess how reward enhancement is involved in high nicotine-amphetamine comorbidity rates and enhanced amphetamine misuse in women.
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Affiliation(s)
- Kathleen R McNealy
- Department of Psychology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
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8
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Robison CL, Kazan T, Miller RLA, Cova N, Charntikov S. Inactivation of posterior but not anterior dorsomedial caudate-putamen impedes learning with self-administered nicotine stimulus in male rats. Behav Brain Res 2021; 413:113438. [PMID: 34224762 DOI: 10.1016/j.bbr.2021.113438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 06/24/2021] [Accepted: 06/27/2021] [Indexed: 11/17/2022]
Abstract
The rodent caudate-putamen is a large heterogeneous neural structure with distinct anatomical connections that differ in their control of learning processes. Previous research suggests that the anterior and posterior dorsomedial caudate-putamen (a- and p-dmCPu) differentially regulate associative learning with a non-contingent nicotine stimulus. The current study used bilateral NMDA-induced excitotoxic lesions to the a-dmCPu and p-dmCPu to determine the functional involvement of a-dmCPu and p-dmCPu in appetitive learning with contingent nicotine stimulus. Rats with a-dmCPu, p-dmCPu, or sham lesions were trained to lever-press for intravenous nicotine (0.03 mg/kg/inf) followed by access to sucrose 30 s later. After 1, 3, 9, and 20 nicotine-sucrose training sessions, appetitive learning in the form of a goal-tracking response was assessed using a non-contingent nicotine-alone test. All rats acquired nicotine self-administration and learned to retrieve sucrose from a receptacle at equal rates. However, rats with lesions to p-dmCPu demonstrated blunted learning of the nicotine-sucrose association. Our primary findings show that rats with lesions to p-dmCPu had a blunted goal-tracking response to a non-contingent nicotine administration after 20 consecutive days of nicotine-sucrose pairing. Our findings extend previous reports to a contingent model of nicotine self-administration and show that p-dmCPu is involved in associative learning with nicotine stimulus using a paradigm where rats voluntarily self-administer nicotine infusions that are paired with access to sucrose-a paradigm that closely resembles learning processes observed in humans.
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Affiliation(s)
| | - Theodore Kazan
- Department of Psychology, University of New Hampshire, United States
| | - Rikki L A Miller
- Department of Psychology, University of Southern Maine, United States
| | - Nicole Cova
- Department of Psychology, University of New Hampshire, United States
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Renda B, Andrade AK, Stone APS, El Azali R, Sharivker M, Khokhar JY, Antenos M, Murray JE. Adolescent nicotine and footshock exposure augments adult nicotine self-administration and drug-seeking without affecting baseline anxiety-like behaviour or stress responsivity in male rats. Psychopharmacology (Berl) 2021; 238:1687-1701. [PMID: 33649967 PMCID: PMC8141046 DOI: 10.1007/s00213-021-05803-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 02/15/2021] [Indexed: 12/30/2022]
Abstract
RATIONALE Over the past decade, adolescent cigarette smoking has been declining. However, adolescent nicotine consumption via electronic cigarettes is rapidly gaining popularity. Earlier onset nicotine use is associated with increased risk of dependence. A bidirectional relationship between nicotine and stress exists; perceived stress is a predictor for nicotine use, and stress reduction is a commonly reported reason for using nicotine. OBJECTIVES We assessed the prolonged impact of adolescent high-dose nicotine and/or footshock exposure on adult nicotine self-administration, anxiety-like behaviour, and hormonal responsivity. METHODS During adolescence (postnatal day [P]28-56) male Sprague-Dawley rats were assigned to one of five groups: saline (SALPRE: 1 ml/kg, SC, every day), nicotine (NICPRE: 1 mg/kg, SC, alternating daily with saline; 14 total nicotine injections), footshock (SHOCKPRE: 8 of 0.5 s, 0.8 mA alternating sessions; saline every day), or combination nicotine and footshock (NIC+SHOCK: concurrent and alternating daily with saline, or NIC-SHOCK: alternating with saline on shock sessions). On P70, one cohort underwent spontaneous intravenous nicotine self-administration (0.03 mg/kg/infusion); another cohort was assessed for open-field behaviour (P71), then corticosterone (CORT) response to nicotine or footshock in adulthood (P72-73). RESULTS Intermittent adolescent nicotine or footshock alone (NICPRE and SHOCKPRE) did not potentiate adult spontaneous nicotine intake compared to SALPRE. However, both combination groups (NIC+SHOCK, NIC-SHOCK) showed increased adult nicotine consumption without associated differences in baseline anxiety-like behaviour or CORT response. CONCLUSIONS Adolescent nicotine and footshock stressors have a synergistic effect on adult nicotine consumption, enhancing nicotine intake. Avenues toward reducing stress in adolescent nicotine users may provide opportunities to reduce vulnerability to adult nicotine consumption.
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Affiliation(s)
- Briana Renda
- Department of Psychology, University of Guelph, Guelph, ON, N1G 2W1, Canada
- Collaborative Neuroscience Program, University of Guelph, Guelph, ON, Canada
| | - Allyson K Andrade
- Department of Psychology, University of Guelph, Guelph, ON, N1G 2W1, Canada
- Collaborative Neuroscience Program, University of Guelph, Guelph, ON, Canada
| | - Adiia P S Stone
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Rita El Azali
- Department of Psychology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Michael Sharivker
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Jibran Y Khokhar
- Collaborative Neuroscience Program, University of Guelph, Guelph, ON, Canada
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada
| | - Monica Antenos
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada
| | - Jennifer E Murray
- Department of Psychology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
- Collaborative Neuroscience Program, University of Guelph, Guelph, ON, Canada.
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Renda B, Andrade AK, Frie JA, Sgarbossa CL, Murray JE, Khokhar JY. High-dose adolescent nicotine exposure permits spontaneous nicotine self-administration in adult male rats. Drug Alcohol Depend 2020; 215:108215. [PMID: 32781311 PMCID: PMC7502504 DOI: 10.1016/j.drugalcdep.2020.108215] [Citation(s) in RCA: 8] [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: 04/25/2020] [Revised: 07/13/2020] [Accepted: 07/23/2020] [Indexed: 12/26/2022]
Abstract
INTRODUCTION While cigarette smoking rates have been steadily decreasing over the past decade, there has been a dramatic increase in nicotine use via e-cigarettes, especially during adolescence. Adolescent e-cigarette use is associated with a greater risk of future cigarette smoking, and increased rates of cigarette smoking in individuals who may have otherwise never tried cigarettes. In humans and rodents, early initiation of nicotine use has been associated with greater consumption, dependence, and persistent nicotine use. The present study sought to investigate the long-lasting effect of daily high-dose nicotine exposure during adolescence on nicotine consumption in adulthood. METHOD Male Sprague-Dawley rats were exposed daily to nicotine (1.0 mg/kg, subcutaneous), or vehicle (1 mL/kg saline, subcutaneous) during adolescence (post-natal day [P] 28-41). Adult nicotine self-administration (0.02 mg/kg/infusion, intravenous) was assessed beginning on P75 on fixed-ratio 1 (FR1), fixed-interval 1 min (FI1), and progressive ratio (PR) schedules of reinforcement. RESULTS Adolescent nicotine pre-exposure did not affect adult nicotine self-administration on the simple FR1 schedule, however increased intake and responding for nicotine was observed when a short delay was implemented on an FI1 schedule of reinforcement. CONCLUSIONS Adolescence is a critical period when the brain is especially vulnerable to the effects of nicotine. Nicotine exposure in adolescence enhances susceptibility to increased nicotine intake in adulthood on a reinforcement schedule more reflective of human nicotine intake patterns, and this effect can extend into adulthood even after termination of nicotine exposure during adolescence.
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Affiliation(s)
- Briana Renda
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Allyson K Andrade
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Jude A Frie
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | | | - Jennifer E Murray
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada.
| | - Jibran Y Khokhar
- Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
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11
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Varenicline rescues nicotine-induced decrease in motivation for sucrose reinforcement. Behav Brain Res 2020; 397:112887. [PMID: 32931838 DOI: 10.1016/j.bbr.2020.112887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/25/2020] [Accepted: 08/26/2020] [Indexed: 11/21/2022]
Abstract
Varenicline is one of the top medications used for smoking cessation and is often prescribed before termination of nicotine use. The effect of this combined nicotine and varenicline use on the reward system and motivation for primary reinforcement is underexplored. The goal of this study was to assess the effects of nicotine and varenicline on motivation for a food reinforcer. In Experiment 1, we first assessed the responding for sucrose after pretreatment with nicotine (0, 0.1, or 0.4 mg/kg) and varenicline (0.0, 0.1, 1.0 mg/kg) using a behavioral economics approach. The responding for sucrose was then assessed using a progressive ratio schedule of reinforcement after pretreatment with all possible combinations of nicotine and varenicline doses. In Experiment 2, rats were assessed for the consumption of sucrose in home cages after pretreatment with nicotine and varenicline. We found that (a) nicotine decreased economic demand for sucrose, (b) varenicline rescued nicotine-induced reduction in economic demand for sucrose, and (c) history of varenicline treatment predicted responding for sucrose on a progressive ratio schedule of reinforcement where rats with a history of varenicline treatment responded significantly lower for sucrose across nicotine doses than rats that had not been exposed to varenicline. The results of Experiment 2 largely confirmed that nicotine decreases motivation for sucrose using a passive consumption protocol and that varenicline rescues this effect. Overall, these findings suggest that varenicline interacts with the effects of nicotine by restoring nicotine-induced reduction in motivation for appetitive rewards.
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