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Parida S, MacLean RR, Gueorguieva R, Sofuoglu M. Pulsed nicotine infusions as a model for smoking: validating a tool to explore nicotine thresholds in humans. Psychopharmacology (Berl) 2024; 241:1915-1922. [PMID: 38970644 DOI: 10.1007/s00213-024-06609-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 05/04/2024] [Indexed: 07/08/2024]
Abstract
RATIONALE No previous studies examined the discriminative stimulus effects of intravenous (IV) nicotine in humans. OBJECTIVES To evaluate a pulsed IV nicotine infusion procedure designed to mimic inhaled nicotine delivery and to identify a range of nicotine doses that may capture the threshold doses for the subjective and discriminative stimulus effects of nicotine. By determining these thresholds, we can gain valuable insights into the addictive threshold of nicotine. METHODS Eleven participants had 2 Test Sessions following overnight abstinence from smoking. Test Session 1 examined participants' ability to discriminate 0.1 mg nicotine/pulse nicotine from saline. Test Session 2 examined if participants can discriminate 0.05, 0.025, and 0.0125 mg nicotine/pulse of nicotine from saline. These nicotine doses were delivered as a cluster of 4 pulsed-nicotine infusions of 2-second duration with a 28-second interval between each pulse. RESULTS The lowest doses of nicotine that produced greater responses than saline for discrimination, subjective effects, and heart rate ranged from 0.05 to 0.1 mg nicotine/pulse. CONCLUSIONS These findings support the validity of our pulsed-infusion procedure as a model for nicotine delivery by smoking and its utility in examining factors that may impact the addictive threshold of nicotine.
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Affiliation(s)
- Suprit Parida
- Department of Psychiatry, School of Medicine, Yale University, New Haven, CT, USA
- VA Connecticut Healthcare System, West Haven, CT, USA
| | - R Ross MacLean
- Department of Psychiatry, School of Medicine, Yale University, New Haven, CT, USA
- VA Connecticut Healthcare System, West Haven, CT, USA
| | - Ralitza Gueorguieva
- Department of Biostatistics, Yale University School of Public Health, New Haven, CT, USA
| | - Mehmet Sofuoglu
- Department of Psychiatry, School of Medicine, Yale University, New Haven, CT, USA.
- VA Connecticut Healthcare System, West Haven, CT, USA.
- Department of Psychiatry, Yale University, VA Connecticut Healthcare System, 950 Campbell Ave., 151D, West Haven, CT, 06516, USA.
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Alkhlaif Y, Shelton KL. Stimulus mediation, specificity and impact of menthol in rats trained to discriminate puffs of nicotine e-cigarette aerosol from nicotine-free aerosol. Psychopharmacology (Berl) 2024; 241:1527-1538. [PMID: 38519818 PMCID: PMC11269472 DOI: 10.1007/s00213-024-06579-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 03/15/2024] [Indexed: 03/25/2024]
Abstract
RATIONALE It is unclear if e-cigarettes have reduced abuse liability relative to traditional cigarettes, especially when considering advanced devices which deliver nicotine more efficiently. Translatable and predictive animal models are needed to addresses this question. OBJECTIVES Our goal was to explore the subjective stimulus effects of e-cigarettes by training rats to discriminate puffs of nicotine aerosol from vehicle aerosol using an aerosol delivery system designed to model e-cigarette use patterns in humans. METHODS Rats were trained to discriminate between ten, 10 s puffs of aerosol generated from 3 mg/ml nicotine e-liquid and nicotine-free e-liquid using a food-reinforced operant procedure. Following acquisition, tests were conducted to determine the specificity of the nicotine aerosol stimulus as well as the impact to the stimulus effects of nicotine resulting from the addition of menthol to e-liquid. RESULTS Rats learned the nicotine aerosol puff vs vehicle puff discrimination in a mean of 25 training sessions. Injected nicotine fully substituted for the stimulus effects of nicotine aerosol. The stimulus effects of nicotine aerosol were blocked by the nicotinic receptor antagonist mecamylamine. The nicotinic receptor partial agonist, varenicline as well as the stimulant d-amphetamine substituted more robustly for nicotine aerosol puffs than did the NMDA antagonist, ketamine. Menthol enhanced the stimulus effects of nicotine aerosol without altering nicotine blood plasma levels. CONCLUSIONS Nicotine aerosol puffs can function as a training stimulus in rats. The stimulus effects were CNS-mediated and receptor specific. Menthol appears to enhance the stimulus effects of nicotine aerosol through a pharmacodynamic rather than pharmacokinetic mechanism.
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Affiliation(s)
- Yasmin Alkhlaif
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, 410 North 12Th Street, Room 746D, Richmond, VA, 23298-0613, USA
| | - Keith L Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, 410 North 12Th Street, Room 746D, Richmond, VA, 23298-0613, USA.
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Withey SL, Pizzagalli DA, Bergman J. Translational In Vivo Assays in Behavioral Biology. Annu Rev Pharmacol Toxicol 2024; 64:435-453. [PMID: 37708432 DOI: 10.1146/annurev-pharmtox-051921-093711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/16/2023]
Abstract
The failure of preclinical research to advance successful candidate medications in psychiatry has created a paradigmatic crisis in psychiatry. The Research Domain Criteria (RDoC) initiative was designed to remedy this situation with a neuroscience-based approach that employs multimodal and cross-species in vivo methodology to increase the probability of translational findings and, consequently, drug discovery. The present review underscores the feasibility of this methodological approach by briefly reviewing, first, the use of multidimensional and cross-species methodologies in traditional behavioral pharmacology and, subsequently, the utility of this approach in contemporary neuroimaging and electrophysiology research-with a focus on the value of functionally homologous studies in nonhuman and human subjects. The final section provides a brief review of the RDoC, with a focus on the potential strengths and weaknesses of its domain-based underpinnings. Optimistically, this mechanistic and multidimensional approach in neuropsychiatric research will lead to novel therapeutics for the management of neuropsychiatric disorders.
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Affiliation(s)
- Sarah L Withey
- Preclinical Behavioral Biology Program, McLean Hospital, Belmont, Massachusetts, USA;
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
- McLean Imaging Center, McLean Hospital, Belmont, Massachusetts, USA
| | - Diego A Pizzagalli
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
- McLean Imaging Center, McLean Hospital, Belmont, Massachusetts, USA
- Center for Depression, Anxiety and Stress Research, McLean Hospital, Belmont, Massachusetts, USA
| | - Jack Bergman
- Preclinical Behavioral Biology Program, McLean Hospital, Belmont, Massachusetts, USA;
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
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Steiner MA, Toeroek-Schafroth M, Giusepponi ME, Dacome L, Tessari M. Abuse potential assessment of the dual orexin receptor antagonist daridorexant in rats. J Psychopharmacol 2023; 37:1249-1260. [PMID: 38059356 PMCID: PMC10714714 DOI: 10.1177/02698811231215415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
BACKGROUND Drugs that act on the central nervous system (CNS) and have sedative effects can lead to abuse in humans. New CNS-active drugs often require evaluation of their abuse potential in dedicated animal models before marketing approval. Daridorexant is a new dual orexin receptor antagonist (DORA) with sleep-promoting properties in animals and humans. It was approved in 2022 in the United States and Europe for the treatment of insomnia disorder. AIMS Nonclinical evaluation of abuse potential of daridorexant using three specific rat models assessing reinforcement, interoception, and withdrawal. METHODS Reinforcing effects of daridorexant were assessed in an operant rat model of intravenous drug self-administration. Similarity of interoceptive effects to those of the commonly used sleep medication zolpidem was tested in an operant drug discrimination task. Withdrawal signs indicative of physical dependence were evaluated upon sudden termination of chronic daridorexant treatment. Rat experiments were conducted at a dose range resulting in daridorexant plasma concentrations equaling or exceeding those achieved at the clinically recommended dose of 50 mg in humans. RESULTS Daridorexant had no reinforcing effects, was dissimilar to zolpidem in the drug discrimination task, and did not induce any withdrawal-related signs upon treatment discontinuation that would be indicative of physical dependence. OUTCOMES Daridorexant showed no signs of abuse or dependence potential in rats. Our data indicate that daridorexant, like other DORAs, has a low potential for abuse in humans.
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Affiliation(s)
| | - Michael Toeroek-Schafroth
- Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
- Current affiliation: Galapagos GmbH, Basel, Switzerland
| | | | - Lisa Dacome
- Aptuit Srl, An Evotec Company, Verona, Italy
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Alkhlaif Y, Shelton KL. Assessment of Abuse-Related Discriminative Stimulus Effects of Nicotine Aerosol in Rodents. J Pharmacol Exp Ther 2023; 385:171-179. [PMID: 36918277 PMCID: PMC10201579 DOI: 10.1124/jpet.122.001520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 01/30/2023] [Accepted: 02/24/2023] [Indexed: 03/16/2023] Open
Abstract
The rapid increase in e-cigarette use highlights the importance of developing relevant, predictive animal models exploring their potential health implications. The goal of the present study was to examine the abuse-related effects of brief, repeated e-cigarette aerosol exposures in rodents modeling human e-cigarette user behavior. We evaluated the discriminative stimulus effects of brief, repeated puffs of inhaled nicotine in rats that had been trained to discriminate injected nicotine from saline. Locomotor activity measurement following exposure to injected and aerosolized nicotine was also assessed as an additional behavioral outcome. We hypothesized that the stimulus effects of nicotine aerosol were central nervous system (CNS)-mediated and comparable to that produced by an injected nicotine training stimulus. We further hypothesized that number of aerosol puffs and the e-liquid nicotine concentration which was aerosolized would impact the substitution of nicotine aerosol for injected nicotine. Both nicotine injections and exposures to nicotine aerosol produced a dose-dependent effect on locomotor activity. Nicotine aerosol under our puffing conditions produced e-liquid nicotine concentration-dependent and puff-number-dependent complete substitution for the injected nicotine training condition. The nicotinic antagonist, mecamylamine, completely blocked nicotine-appropriate responding produce by the training dose of 0.3 mg/kg injected nicotine as well as that resulting from exposure to aerosol puffs generated by e-liquid containing 3 mg/ml nicotine, demonstrating that the stimulus of inhaled nicotine was most likely CNS-mediated and not due to olfactory stimulus properties. Overall, the results support the hypothesis that an aerosol exposure drug discrimination model in rodents has applicability to studying the abuse-related effects of e-cigarettes. SIGNIFICANCE STATEMENT: Animal models of nicotine aerosol exposure using testing conditions resembling human e-cigarette use are lacking. In this study, we test a novel preclinical model of nicotine vaping in rodents which allows for the exploration of the abuse-related effects of e-cigarettes. This model has the potential to contribute both to our understanding of the abuse-related pharmacological effects of e-cigarettes as well as aid in the development of rationale, evidence-based e-cigarette regulatory policies.
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Affiliation(s)
- Yasmin Alkhlaif
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Keith L Shelton
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Tyler RE, Bluitt MN, Van Voorhies K, Ornelas LC, Weinberg BZS, Besheer J. Predator odor (TMT) exposure potentiates interoceptive sensitivity to alcohol and increases GABAergic gene expression in the anterior insular cortex and nucleus accumbens in male rats. Alcohol 2022; 104:1-11. [PMID: 36150613 PMCID: PMC9733390 DOI: 10.1016/j.alcohol.2022.07.002] [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: 02/17/2022] [Revised: 06/03/2022] [Accepted: 07/06/2022] [Indexed: 01/26/2023]
Abstract
Post-traumatic stress disorder (PTSD) confers enhanced vulnerability to developing comorbid alcohol use disorder (AUD). Exposure to the scent of a predator, such as the fox odor TMT, has been used to model a traumatic stressor with relevance to PTSD symptomatology. Alcohol produces distinct interoceptive (subjective) effects that may influence vulnerability to problem drinking and AUD. As such, understanding the lasting impact of stressors on sensitivity to the interoceptive effects of alcohol is clinically relevant. The present study used a 2-lever, operant drug discrimination procedure to train male Long-Evans rats to discriminate the interoceptive effects of alcohol (2 g/kg, i.g. [intragastrically]) from water. Upon stable performance, rats underwent a 15-min exposure to TMT. Two weeks later, an alcohol dose-response curve was conducted to evaluate the lasting effects of the TMT stressor on the interoceptive effects of alcohol. The TMT group showed a leftward shift in the effective dose (ED50) of the dose-response curve compared to controls, reflecting potentiated interoceptive sensitivity to alcohol. TMT exposure did not affect response rate. GABAergic signaling in both the anterior insular cortex (aIC) and the nucleus accumbens (Acb) is involved in the interoceptive effects of alcohol and stressor-induced adaptations. As such, follow-up experiments in alcohol-naïve rats examined neuronal activation (as measured by c-Fos immunoreactivity) following TMT and showed that TMT exposure increased c-Fos expression in the aIC and the nucleus accumbens core (AcbC). Two weeks after TMT exposure, Gad-1 gene expression was elevated in the aIC and Gat-1 was increased in the Acb, compared to controls. Lastly, the alcohol discrimination and alcohol-naïve groups displayed dramatic differences in stress reactive behaviors during the TMT exposure, suggesting that alcohol exposure may alter the behavioral response to predator odor. Together, these data suggest that predator odor stressor results in potentiated sensitivity to alcohol, possibly through GABAergic adaptations in the aIC and Acb, which may be relevant to understanding PTSD-AUD comorbidity.
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Affiliation(s)
- Ryan E Tyler
- Neuroscience Curriculum, School of Medicine, University of North Carolina - Chapel Hill, Chapel Hill, NC, United States; Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Maya N Bluitt
- Neuroscience Curriculum, School of Medicine, University of North Carolina - Chapel Hill, Chapel Hill, NC, United States; Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Kalynn Van Voorhies
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Laura C Ornelas
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Benjamin Z S Weinberg
- Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Joyce Besheer
- Neuroscience Curriculum, School of Medicine, University of North Carolina - Chapel Hill, Chapel Hill, NC, United States; Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina, Chapel Hill, NC, United States; Department of Psychiatry, School of Medicine, University of North Carolina - Chapel Hill, Chapel Hill, NC, United States.
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Stoops WW. A Brief Introduction to Human Behavioral Pharmacology: Methods, Design Considerations and Ethics. Perspect Behav Sci 2022; 45:361-381. [PMID: 35719875 PMCID: PMC9163231 DOI: 10.1007/s40614-022-00330-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/11/2022] [Indexed: 11/25/2022] Open
Abstract
Human behavioral pharmacology methods have been used to rigorously evaluate the effects of a range of centrally acting drugs in humans under controlled conditions for decades. Methods like drug self-administration and drug discrimination have been adapted from nonhuman laboratory animal models. Because humans have the capacity to communicate verbally, self-report methods are also commonly used to understand drug effects. This perspective article provides an overview of these traditional human behavioral pharmacology methods and introduces some novel methodologies that have more recently been adapted for use in the field. Design (e.g., using placebo controls, testing multiple doses) and ethical (e.g., avoiding enrollment of individuals seeking treatment, determining capacity to consent) considerations that must be addressed when conducting these types of studies are also described.
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Affiliation(s)
- William W. Stoops
- University of Kentucky, 1100 Veterans Drive, Medical Behavioral Science Building Room 140, Lexington, KY 40536-0086 USA
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van den Berg M, Magaraggia I, Schreiber R, Hillhouse TM, Porter JH. How to account for hallucinations in the interpretation of the antidepressant effects of psychedelics: a translational framework. Psychopharmacology (Berl) 2022; 239:1853-1879. [PMID: 35348806 PMCID: PMC9166823 DOI: 10.1007/s00213-022-06106-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 02/24/2022] [Indexed: 01/02/2023]
Abstract
RATIONALE Recent trials with psychedelics in major depressive disorder and treatment-resistant depression showed remarkable improvements in depressive symptoms that can last for up to several months after even a single administration. The lack of an appropriate placebo control group-as patients are often able to discriminate the subjective effects of the drug-and an incomplete understanding of the role of the hallucinogenic and mystical experience, hampers the interpretation of these therapeutic effects. OBJECTIVES To control for these factors, we developed a translational framework based on establishing pharmacokinetic/pharmacodynamic (PK/PD) relationships in rodents and humans for hallucinogenic (i.e., discriminative stimulus effects in rodents and humans; head twitch responses in rodents; questionnaires in humans) and therapeutic effects. For the latter, we selected the pattern separation and attentional set-shifting tasks as measures for cognitive flexibility because of their high translational value. We predict that these PK/PD analyses will lead to a more objective evaluation of improvements in patients compared to relying only on the currently used self-reported questionnaires. We hypothesize that-if the role of the hallucinogenic experience is not central in the antidepressant effects of psychedelics-the ED50's for the therapeutic effects will be significantly lower than for the hallucinogenic and mystical effects. CONCLUSION Our framework will help to inform future studies that aim at the elucidation of the mechanism(s) of action of psychedelics in depression, and the role of the acute subjective and/or hallucinogenic experience in their effects.
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Affiliation(s)
- Manon van den Berg
- Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands ,Faculty of Psychology and Neuroscience, Section Neuropsychology & Psychopharmacology, Maastricht University, Maastricht, The Netherlands
| | - Igor Magaraggia
- Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands ,Faculty of Psychology and Neuroscience, Section Neuropsychology & Psychopharmacology, Maastricht University, Maastricht, The Netherlands
| | - Rudy Schreiber
- Faculty of Psychology and Neuroscience, Section Neuropsychology & Psychopharmacology, Maastricht University, Maastricht, The Netherlands.
| | - Todd M. Hillhouse
- Department of Psychology, University of Wisconsin Green Bay, Green Bay, WI USA
| | - Joseph H. Porter
- Department of Psychology, Virginia Commonwealth University, Richmond, USA
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Interoception and alcohol: Mechanisms, networks, and implications. Neuropharmacology 2021; 200:108807. [PMID: 34562442 DOI: 10.1016/j.neuropharm.2021.108807] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 09/20/2021] [Accepted: 09/21/2021] [Indexed: 01/25/2023]
Abstract
Interoception refers to the perception of the internal state of the body and is increasingly being recognized as an important factor in mental health disorders. Drugs of abuse produce powerful interoceptive states that are upstream of behaviors that drive and influence drug intake, and addiction pathology is impacted by interoceptive processes. The goal of the present review is to discuss interoceptive processes related to alcohol. We will cover physiological responses to alcohol, how interoceptive states can impact drinking, and the recruitment of brain networks as informed by clinical research. We also review the molecular and brain circuitry mechanisms of alcohol interoceptive effects as informed by preclinical studies. Finally, we will discuss emerging treatments with consideration of interoception processes. As our understanding of the role of interoception in drug and alcohol use grows, we suggest that the convergence of information provided by clinical and preclinical studies will be increasingly important. Given the complexity of interoceptive processing and the multitude of brain regions involved, an overarching network-based framework can provide context for how focused manipulations modulate interoceptive processing as a whole. In turn, preclinical studies can systematically determine the roles of individual nodes and their molecular underpinnings in a given network, potentially suggesting new therapeutic targets and directions. As interoceptive processing drives and influences motivation, emotion, and subsequent behavior, consideration of interoception is important for our understanding of processes that drive ongoing drinking and relapse.
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10
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Hypothalamic control of interoceptive hunger. Curr Biol 2021; 31:3797-3809.e5. [PMID: 34273280 DOI: 10.1016/j.cub.2021.06.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 05/06/2021] [Accepted: 06/16/2021] [Indexed: 01/08/2023]
Abstract
While energy balance is critical to survival, many factors influence food intake beyond caloric need or "hunger." Despite this, some neurons that drive feeding in mice are routinely referred to as "hunger neurons," whereas others are not. To understand how specific hypothalamic circuits control interoceptive hunger, we trained mice to discriminate fasted from sated periods. We then manipulated three hypothalamic neuronal populations with well-known effects on feeding while mice performed this task. While activation of ARCAGRP neurons in sated mice caused mice to report being food-restricted, LHVGAT neuron activation or LHVGLUT2 neuron inhibition did not. In contrast, LHVGAT neuron inhibition or LHVGLUT2 neuron activation in fasted mice attenuated natural hunger, whereas ARCAGRP neuron inhibition did not. Each neuronal population evoked distinct effects on food consumption and reward. After satiety- or sickness-induced devaluation, ARCAGRP neurons drove calorie-specific feeding, while LHVGAT neurons drove calorie-indiscriminate food intake. Our data support a role for ARCAGRP neurons in homeostatic feeding and implicate them in driving a hunger-like internal state that directs behavior toward caloric food sources. Moreover, manipulations of LH circuits did not evoke hunger-like effects in sated mice, suggesting that they may govern feeding more related to reward, compulsion, or generalized consumption than to energy balance, but also that these LH circuits can be powerful negative appetite modulators in fasted mice. This study highlights the complexity of hypothalamic feeding regulation and can be used as a framework to characterize how other neuronal circuits affect hunger and identify potential therapeutic targets for eating disorders.
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Jin B, Alam M, Tierno A, Zhong H, Roy RR, Gerasimenko Y, Lu DC, Edgerton VR. Serotonergic Facilitation of Forelimb Functional Recovery in Rats with Cervical Spinal Cord Injury. Neurotherapeutics 2021; 18:1226-1243. [PMID: 33420588 PMCID: PMC8423890 DOI: 10.1007/s13311-020-00974-8] [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] [Subscribe] [Scholar Register] [Accepted: 11/14/2020] [Indexed: 10/22/2022] Open
Abstract
Serotonergic agents can improve the recovery of motor ability after a spinal cord injury. Herein, we compare the effects of buspirone, a 5-HT1A receptor partial agonist, to fluoxetine, a selective serotonin reuptake inhibitor, on forelimb motor function recovery after a C4 bilateral dorsal funiculi crush in adult female rats. After injury, single pellet reaching performance and forelimb muscle activity decreased in all rats. From 1 to 6 weeks after injury, rats were tested on these tasks with and without buspirone (1-2 mg/kg) or fluoxetine (1-5 mg/kg). Reaching and grasping success rates of buspirone-treated rats improved rapidly within 2 weeks after injury and plateaued over the next 4 weeks of testing. Electromyography (EMG) from selected muscles in the dominant forelimb showed that buspirone-treated animals used new reaching strategies to achieve success after the injury. However, forelimb performance dramatically decreased within 2 weeks of buspirone withdrawal. In contrast, fluoxetine treatment resulted in a more progressive rate of improvement in forelimb performance over 8 weeks after injury. Neither buspirone nor fluoxetine significantly improved quadrupedal locomotion on the horizontal ladder test. The improved accuracy of reaching and grasping, patterns of muscle activity, and increased excitability of spinal motor-evoked potentials after buspirone administration reflect extensive reorganization of connectivity within and between supraspinal and spinal sensory-motor netxcopy works. Thus, both serotonergic drugs, buspirone and fluoxetine, neuromodulated these networks to physiological states that enabled markedly improved forelimb function after cervical spinal cord injury.
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Affiliation(s)
- Benita Jin
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
| | - Monzurul Alam
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
| | - Alexa Tierno
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
| | - Hui Zhong
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
| | - Roland R Roy
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Yury Gerasimenko
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA
- Pavlov Institute of Physiology, St. Petersburg, 199034, Russia
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, 420006, Russia
| | - Daniel C Lu
- Department of Neurosurgery, University of California, Los Angeles, CA, 90095, USA
| | - V Reggie Edgerton
- Department of Integrative Biology and Physiology, University of California, Los Angeles, 610 Charles E. Young Drive, Los Angeles, CA, 90095-1527, USA.
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
- Department of Neurosurgery, University of California, Los Angeles, CA, 90095, USA.
- Department of Neurobiology, University of California, Los Angeles, CA, 90095, USA.
- Faculty of Science, The Centre for Neuroscience and Regenerative Medicine, University of Technology Sydney, Ultimo, NSW, Australia.
- Institut Guttmann, Hospital de Neurorehabilitació, Institut Universitari adscript a la Universitat Autònoma de Barcelona, 08916, Badalona, Spain.
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Popik P, Khoo SYS, Kuziak A, Golebiowska J, Potasiewicz A, Hogendorf A, Popik O, Matloka M, Moszczynski R, Nikiforuk A, Witkin JM. Distinct cognitive and discriminative stimulus effects of ketamine enantiomers in rats. Pharmacol Biochem Behav 2020; 197:173011. [PMID: 32758523 DOI: 10.1016/j.pbb.2020.173011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 07/01/2020] [Accepted: 07/31/2020] [Indexed: 01/21/2023]
Abstract
Although (S)-ketamine was approved for use in treatment-resistant depression in 2019, new preclinical findings suggest that (R)-ketamine might produce better efficacy and tolerability relative to (S)-ketamine. Here we evaluated the effects of (R)-, (S)-, and (R,S)-ketamine on executive functions as measured in the attentional set shifting task (ASST) and on their discriminative stimulus effects in rats. Earlier data demonstrated that cognitive flexibility is compromised by (R,S)-ketamine, but the effects of enantiomers in rats are unknown. Separate cohorts of rats were tested in ASST and trained to discriminate either (R,S)-ketamine, (S)-ketamine, or (R)-ketamine (all at 10 mg/kg) from saline; in order to maintain the discrimination, a higher (R)-ketamine dose (17.5 mg/kg) was subsequently instituted. In ASST, all three forms increased the trials to criterion measure at reversal learning and extra-dimensional set-shifting phases. However, in contrast to (R)- and (S)-ketamine, (R,S)-ketamine prolonged the mean time to complete a single trial during early stages, suggesting increased reaction time, and/or unspecific side-effects related to motor or motivational impairments. In the drug discriminations, all rats acquired their respective discriminations between drug and saline. In (R,S)-ketamine-trained rats, (R)-ketamine and (S)-ketamine only partially substituted for the training dose of (R,S)-ketamine. Further, (R)-ketamine did not fully substitute in rats trained to (S)-ketamine. The data suggest more serious cognitive deficits produced by (R,S)-ketamine than its enantiomers. Furthermore, (R,S)-ketamine and its isomers share overlapping but not isomorphic discriminative stimulus effects predicting distinct subjective responses to (R)- vs. (S)-ketamine in humans.
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Affiliation(s)
- Piotr Popik
- Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland.
| | - Shaun Yon-Seng Khoo
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Agata Kuziak
- Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Joanna Golebiowska
- Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Agnieszka Potasiewicz
- Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Adam Hogendorf
- Department of Medicinal Chemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Oskar Popik
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa, Poland
| | | | | | - Agnieszka Nikiforuk
- Behavioral Neuroscience and Drug Development, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, 31-343 Kraków, Poland
| | - Jeffrey M Witkin
- Department of Neuroscience, Ascension St. Vincent Hospital, Indianapolis, IN, USA; Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA; Department of Trauma Research, Ascension St. Vincent Hospital, Indianapolis, IN, USA
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13
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Shellenberg TP, Stoops WW, Lile JA, Rush CR. An update on the clinical pharmacology of methylphenidate: therapeutic efficacy, abuse potential and future considerations. Expert Rev Clin Pharmacol 2020; 13:825-833. [PMID: 32715789 DOI: 10.1080/17512433.2020.1796636] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Methylphenidate remains a first-line medication for treating ADHD in children and adults. However, its behavioral pharmacological similarities to methamphetamine and cocaine have historically created concern for its potential as a drug of abuse. In September 2019, the FDA published a docket requesting comments for the development of abuse deterrent formulations for CNS stimulants, emphasizing the abuse of methylphenidate as a public health concern. AREAS COVERED We conducted a narrative review of research on the clinical pharmacology, therapeutic efficacy, and abuse potential of methylphenidate. EXPERT OPINION Several studies indicate that methylphenidate has at least some abuse potential. Methylphenidate, amphetamine, methamphetamine, and cocaine overlap in their subjective, reinforcing, and discriminative stimulus effects. Regardless, methylphenidate remains an efficacious treatment for ADHD in children and adults when properly adhered to, especially when paired with non-pharmacological treatments. The development of abuse deterrent formulations of methylphenidate is warranted.
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Affiliation(s)
- Thomas P Shellenberg
- Department of Behavioral Science, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychiatry, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychology, College of Arts and Sciences, University of Kentucky , Lexington, KY, USA
| | - William W Stoops
- Department of Behavioral Science, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychiatry, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychology, College of Arts and Sciences, University of Kentucky , Lexington, KY, USA
| | - Joshua A Lile
- Department of Behavioral Science, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychiatry, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychology, College of Arts and Sciences, University of Kentucky , Lexington, KY, USA
| | - Craig R Rush
- Department of Behavioral Science, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychiatry, College of Medicine, University of Kentucky , Lexington, KY, USA.,Department of Psychology, College of Arts and Sciences, University of Kentucky , Lexington, KY, USA
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14
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Mead J, Parrott A. Mephedrone and MDMA: A comparative review. Brain Res 2020; 1735:146740. [PMID: 32087112 DOI: 10.1016/j.brainres.2020.146740] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 02/13/2020] [Accepted: 02/18/2020] [Indexed: 01/10/2023]
Abstract
Mephedrone and MDMA are both constituents of party drugs, with mephedrone being relatively new compared to MDMA. This review compares current knowledge regarding the patterns of usage and neuropsychobiological effects of both mephedrone and MDMA. Both drugs share common psychoactive effects, the duration of which is significantly shorter with mephedrone use, attributing towards a pattern of binge use among users. Both drugs have also been associated with adverse health, psychiatric, and neurocognitive problems. Whilst there is extensive research into the psychobiological problems induced by MDMA, the evidence for mephedrone is comparatively limited. The adverse effect profile of mephedrone appears to be less severe than that of MDMA. Users often believe it to be safer, although both drugs have been associated with overdoses. The neurotoxic potential of mephedrone appears to be low, whereas MDMA can cause long-term damage to the serotonergic system, although this needs further investigation. The abuse liability of mephedrone is significantly greater than that of MDMA, raising concerns regarding the impact of lifetime usage on users. Given that mephedrone is relatively new, the effects of long-term exposure are yet to be documented. Future research focused on lifetime users may highlight more severe neuropsychobiological effects from the drug.
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Affiliation(s)
- Jessica Mead
- Department of Psychology, School of Human and Health Sciences, Swansea University, Swansea, Wales, United Kingdom.
| | - Andrew Parrott
- Department of Psychology, School of Human and Health Sciences, Swansea University, Swansea, Wales, United Kingdom
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15
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Allen DC, Ford MM, Grant KA. Cross-Species Translational Findings in the Discriminative Stimulus Effects of Ethanol. Curr Top Behav Neurosci 2019; 39:95-111. [PMID: 28341943 PMCID: PMC5612861 DOI: 10.1007/7854_2017_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The progress on understanding the pharmacological basis of ethanol's discriminative stimulus effects has been substantial, but appears to have plateaued in the past decade. Further, the cross-species translational efforts are clear in laboratory animals, but have been minimal in human subject studies. Research findings clearly demonstrate that ethanol produces a compound stimulus with primary activity through GABA and glutamate receptor systems, particularly ionotropic receptors, with additional contribution from serotonergic mechanisms. Further progress should capitalize on chemogenetic and optogenetic techniques in laboratory animals to identify the neural circuitry involved in mediating the discriminative stimulus effects of ethanol. These infrahuman studies can be guided by in vivo imaging of human brain circuitry mediating ethanol's subjective effects. Ultimately, identifying receptors systems, as well as where they are located within brain circuitry, will transform the use of drug discrimination procedures to help identify possible treatment or prevention strategies for alcohol use disorder.
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Affiliation(s)
- Daicia C Allen
- Department of Behavioral Neurosciences, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Matthew M Ford
- Department of Behavioral Neurosciences, Oregon Health & Science University, Portland, OR, 97239, USA
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, 97006, USA
| | - Kathleen A Grant
- Department of Behavioral Neurosciences, Oregon Health & Science University, Portland, OR, 97239, USA.
- Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, 97006, USA.
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16
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Porter JH, Prus AJ, Overton DA. Drug Discrimination: Historical Origins, Important Concepts, and Principles. Curr Top Behav Neurosci 2019; 39:3-26. [PMID: 29637526 DOI: 10.1007/7854_2018_40] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
Research on the stimulus properties of drugs began with studies on state dependent learning during the first half of the twentieth century. From that research, an entirely new approach evolved called drug discrimination. Animals (including humans) could discriminate the presence or absence of a drug; once learned, the drug could serve as a discriminative stimulus, signaling the availability or nonavailability of reinforcement. Early drug discrimination research involved the use of a T-maze task, which evolved in the 1970s into a two-lever operant drug discrimination task that is still used today. A number of important concepts and principles of drug discrimination are discussed. (1) The discriminative stimulus properties of drugs are believed in large part to reflect the subjective effects of drugs. While it has been impossible to directly measure subjective effects in nonhuman animals, drug discrimination studies in human subjects have generally supported the belief that discriminative stimulus properties of drugs in nonhuman animals correlate highly with subjective effects of drugs in humans. In addition to the ability of the drug discrimination procedure to measure the subjective effects of drugs, it has a number of other strengths that help make it a valuable preclinical assay. (2) Drug discrimination can be used for classification of drugs based on shared discriminative stimulus properties. (3) The phenomena of tolerance and cross-tolerance can be studied with drug discrimination. (4) Discriminative stimulus properties of drugs typically have been found to be stereospecific, if a drug is comprised of enantiomers. (5) Discriminative stimulus properties of drugs reflect specific CNS activity at neurotransmitter receptors. (6) Both human and nonhuman subjects display individual differences in their sensitivity to discriminative stimuli and drugs. (7) The drug discrimination procedure has been used extensively as a preclinical assay in drug development. This chapter is the first in the volume The Behavioural Neuroscience of Drug Discrimination, which includes chapters concerning the discriminative stimulus properties of various classes of psychoactive drugs as well as sections on the applications and approaches for using this procedure.
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Affiliation(s)
- Joseph H Porter
- Department of Psychology, Virginia Commonwealth University, Richmond, VA, USA.
| | - Adam J Prus
- Northern Michigan University, Marquette, MI, USA
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17
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Chandler CM, Overton JS, Rüedi-Bettschen D, Platt DM. GABA A Receptor Subtype Mechanisms and the Abuse-Related Effects of Ethanol: Genetic and Pharmacological Evidence. Handb Exp Pharmacol 2018; 248:3-27. [PMID: 29204713 DOI: 10.1007/164_2017_80] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ethanol's reinforcing and subjective effects, as well as its ability to induce relapse, are powerful factors contributing to its widespread use and abuse. A significant mediator of these behavioral effects is the GABAA receptor system. GABAA receptors are the target for γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the CNS. Structurally, they are pentameric, transmembrane chloride ion channels comprised of subunits from at least eight different families of distinct proteins. The contribution of different GABAA subunits to ethanol's diverse abuse-related effects is not clear and remains an area of research focus. This chapter details the clinical and preclinical findings supporting roles for different α, β, γ, and δ subunit-containing GABAA receptors in ethanol's reinforcing, subjective/discriminative stimulus, and relapse-inducing effects. The reinforcing properties of ethanol have been studied the most systematically, and convergent preclinical evidence suggests a key role for the α5 subunit in those effects. Regarding ethanol's subjective/discriminative stimulus effects, clinical and genetic findings support a primary role for the α2 subunit, whereas preclinical evidence implicates the α5 subunit. At present, too few studies investigating ethanol relapse exist to make any solid conclusions regarding the role of specific GABAA subunits in this abuse-related effect.
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Affiliation(s)
- Cassie M Chandler
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA
| | - John S Overton
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Daniela Rüedi-Bettschen
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Donna M Platt
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA.
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA.
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18
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Perkins KA, Kunkle N, Karelitz JL, Perkins KA, Kunkle N, Karelitz JL. Preliminary test of cigarette nicotine discrimination threshold in non-dependent versus dependent smokers. Drug Alcohol Depend 2017; 175:36-41. [PMID: 28380366 PMCID: PMC5480896 DOI: 10.1016/j.drugalcdep.2017.01.033] [Citation(s) in RCA: 14] [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: 01/09/2017] [Revised: 01/24/2017] [Accepted: 01/24/2017] [Indexed: 12/31/2022]
Abstract
BACKGROUND Despite its potential for understanding tobacco dependence, behavioral discrimination of nicotine via smoking has not been formally examined as a function of nicotine dependence level. METHODS Spectrum research cigarettes were used to compare non-dependent with dependent smokers on the lowest content of nicotine they could discriminate (i.e., "threshold"). Dependent (n=21; 16M, 5F) or non-dependent (n=7; 4M, 3F) smokers were tested on ability to discriminate between cigarettes with nicotine contents of 17, 11, 5, 2, and 1mg/g, one per session, from an "ultra-low" cigarette with 0.4mg/g (all had 9-10mg "tar"). All abstained from smoking overnight prior to sessions, and number of sessions was determined by the lowest nicotine content they could reliably discriminate from the ultra-low on >80% of trials (i.e., ≥5 of 6). Subjective perceptions and cigarette choice behavior were also assessed and related to discrimination behavior. RESULTS Discrimination thresholds (and most perceptions) did not differ between dependent and non-dependent smokers, with median thresholds of 11mg/g for both subgroups. Yet, "liking" and puff choice for threshold cigarettes were greater in dependent but not non-dependent smokers, while cigarettes with nicotine contents below threshold did not support "liking" or choice in both groups. CONCLUSIONS In sum, this preliminary study suggests threshold for discriminating nicotine via smoking may not vary by dependence level, and further study is needed to confirm that cigarettes unable to be discriminated are also not reinforcing.
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Affiliation(s)
- Kenneth A Perkins
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA.
| | - Nicole Kunkle
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - Joshua L Karelitz
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - K A Perkins
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - N Kunkle
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - J L Karelitz
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
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19
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Perkins KA, Kunkle N, Karelitz JL. Threshold dose for behavioral discrimination of cigarette nicotine content in menthol vs. non-menthol smokers. Psychopharmacology (Berl) 2017; 234:1255-1265. [PMID: 28210778 DOI: 10.1007/s00213-017-4563-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 02/03/2017] [Indexed: 01/01/2023]
Abstract
RATIONALE The lowest threshold content (or "dose") of nicotine discriminated in cigarettes may differ due to menthol preference. OBJECTIVES Menthol and non-menthol Spectrum research cigarettes differing in nicotine content were used to determine discrimination thresholds. METHODS Dependent smokers preferring menthol (n = 40) or non-menthol (n = 21) brands were tested on ability to discriminate cigarettes (matched for their menthol preference) with nicotine contents of 16-17, 11-12, 5, 2, and 1 mg/g, one per session, from an "ultra-low" cigarette with 0.4 mg/g. Controlled exposure to each cigarette was four puffs/trial, and the number of sessions was determined by the lowest nicotine content they could discriminate on >80% of trials (i.e., ≥5 of 6). We also assessed subjective perceptions and behavioral choice between cigarettes to relate them to discrimination responses. RESULTS Controlling for Fagerstrom Test of Nicotine Dependence score, discrimination thresholds were more likely to be at higher nicotine content cigarettes for menthol vs. non-menthol smokers (p < .005), with medians of 16 vs. 11 mg/g, respectively. Compared to the ultra-low, threshold and subthreshold (next lowest) cigarettes differed on most perceptions and puff choice, but menthol preference did not alter these associations. Notably, threshold cigarettes did, but subthreshold did not, increase choice over the ultra-low. CONCLUSIONS Threshold for discriminating nicotine via smoking may be generally higher for menthol vs. non-menthol smokers. More research is needed to identify why menthol smoking is related to higher nicotine thresholds and to verify that cigarettes unable to be discriminated do not support reinforcement.
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Affiliation(s)
- Kenneth A Perkins
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA, 15213, USA.
| | - Nicole Kunkle
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA, 15213, USA
| | - Joshua L Karelitz
- Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, 3811 O'Hara Street, Pittsburgh, PA, 15213, USA
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