1
|
Maccioni P, Bratzu J, Lobina C, Acciaro C, Corrias G, Capra A, Carai MAM, Agabio R, Muntoni AL, Gessa GL, Colombo G. Exposure to an enriched environment reduces alcohol self-administration in Sardinian alcohol-preferring rats. Physiol Behav 2022; 249:113771. [PMID: 35247441 DOI: 10.1016/j.physbeh.2022.113771] [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: 12/15/2021] [Revised: 02/28/2022] [Accepted: 02/28/2022] [Indexed: 10/19/2022]
Abstract
Living in an enriched environment (EE) produces a notable impact on several rodent behaviors, including those motivated by drugs of abuse. This picture is somewhat less clear when referring to alcohol-motivated behaviors. With the intent of contributing to this research field with data from one of the few rat lines selectively bred for excessive alcohol consumption, the present study investigated the effect of EE on operant oral alcohol self-administration in Sardinian alcohol-preferring (sP) rats. Starting from Postnatal Day (PND) 21, male sP rats were kept under 3 different housing conditions: impoverished environment (IE; single housing in shoebox-like cages with no environmental enrichment); standard environment (SE; small colony cages with 3 rats and no environmental enrichment); EE (large colony cages with 6 rats and multiple elements of environmental enrichment, including 2 floors, ladders, maze, running wheels, and shelter). From PND 60, rats were exposed to different phases of shaping and training of alcohol self-administration. IE, SE, and EE rats were then compared under (i) fixed ratio (FR) 4 (FR4) schedule of alcohol reinforcement for 20 daily sessions and (ii) progressive ratio (PR) schedule of alcohol reinforcement in a final single session. Acquisition of the lever-responding task (shaping) was slower in EE than IE and SE rats, as the likely consequence of a "devaluation" of the novel stimuli provided by the operant chamber in comparison to those to which EE rats were continuously exposed in their homecage or an alteration, induced by EE, of the rat "emotionality" state when facing the novel environment represented by the operant chamber. Training of alcohol self-administration was slower in EE than IE rats, with SE rats displaying intermediate values. A similar ranking order (IE>SE>EE) was also observed in number of lever-responses for alcohol, amount of self-administered alcohol, and breakpoint for alcohol under FR4 and PR schedules of reinforcement. These data suggest that living in a complex environment reduced the reinforcing and motivational properties of alcohol in sP rats. These results are interpreted in terms of the reinforcing and motivational properties of the main components of EE (i.e., social interactions, physical activities, exploration, novelty) substituting, at least partially, for those of alcohol.
Collapse
Affiliation(s)
- Paola Maccioni
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy
| | - Jessica Bratzu
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy
| | - Carla Lobina
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy
| | - Carla Acciaro
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy
| | - Gianluigi Corrias
- Department of Physics, University of Cagliari, I-09042 Monserrato (CA), Italy
| | - Alessandro Capra
- Department of Biomedical Sciences, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, I-09042 Monserrato (CA), Italy
| | - Mauro A M Carai
- Cagliari Pharmacological Research, I-09127 Cagliari (CA), Italy
| | - Roberta Agabio
- Department of Biomedical Sciences, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, I-09042 Monserrato (CA), Italy
| | - Anna Lisa Muntoni
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy
| | - Gian Luigi Gessa
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy; Department of Biomedical Sciences, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, I-09042 Monserrato (CA), Italy
| | - Giancarlo Colombo
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042 Monserrato (CA), Italy.
| |
Collapse
|
2
|
Bowen MT, George O, Muskiewicz DE, Hall FS. FACTORS CONTRIBUTING TO THE ESCALATION OF ALCOHOL CONSUMPTION. Neurosci Biobehav Rev 2022; 132:730-756. [PMID: 34839930 PMCID: PMC8892842 DOI: 10.1016/j.neubiorev.2021.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/05/2021] [Accepted: 11/12/2021] [Indexed: 01/03/2023]
Abstract
Understanding factors that contribute to the escalation of alcohol consumption is key to understanding how an individual transitions from non/social drinking to AUD and to providing better treatment. In this review, we discuss how the way ethanol is consumed as well as individual and environmental factors contribute to the escalation of ethanol consumption from intermittent low levels to consistently high levels. Moreover, we discuss how these factors are modelled in animals. It is clear a vast array of complex, interacting factors influence changes in alcohol consumption. Some of these factors act early in the acquisition of ethanol consumption and initial escalation, while others contribute to escalation of ethanol consumption at a later stage and are involved in the development of alcohol dependence. There is considerable need for more studies examining escalation associated with the formation of dependence and other hallmark features of AUD, especially studies examining mechanisms, as it is of considerable relevance to understanding and treating AUD.
Collapse
Affiliation(s)
- Michael T. Bowen
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, 2050, Australia,The University of Sydney, Faculty of Science, School of Psychology, Sydney, NSW, 2006, Australia,Corresponding Author: Michael T. Bowen, Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, Sydney, NSW, 2050, Australia,
| | - Olivier George
- Department of Psychology, University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Dawn E. Muskiewicz
- Department of Pharmacology & Experimental Therapeutics, College of Pharmacology and Pharmacological Science, University of Toledo, OH, USA
| | - F. Scott Hall
- Department of Pharmacology & Experimental Therapeutics, College of Pharmacology and Pharmacological Science, University of Toledo, OH, USA
| |
Collapse
|
3
|
Ballaz S, Espinosa N, Bourin M. Does endogenous cholecystokinin modulate alcohol intake? Neuropharmacology 2021; 193:108539. [PMID: 33794246 DOI: 10.1016/j.neuropharm.2021.108539] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/06/2021] [Accepted: 03/22/2021] [Indexed: 02/08/2023]
Abstract
Alcohol use disorder or alcoholism is characterized by uncontrollable alcohol use and intoxication, as well as a heightened state of anxiety after alcohol withdrawal. Ethanol-associated stimuli also drive the urge to drink by means of classical conditioning. Alcoholism has been considered a dopamine (DA) dysregulation syndrome that involves the activity of the central amygdala circuitry of anxiety. Cholecystokinin (CCK) is the most abundant neuropeptide in the mammal brain, where it activates two receptors, CCK1 and CCK2. Genetic evidence relates CCK1 receptors to alcoholism in humans. CCK2 activity has been associated with the onset of human anxiety. CCK modulates DA release in the nucleus accumbens (NAc) and it is expressed in the γ-aminobutyric acid (GABA)-expressing basket interneurons in the cerebral cortex. CCK interacts with serotonin (5-HT) neurotransmission through 5-HT3 receptors to regulate mesocorticolimbic pathways and with GABA to attenuate anxiety in the amygdala. Finally, CCK stimulates the release of orexins and oxytocin in the hypothalamus, two relevant hypothalamic neuropeptides involved in signaling satiety for ethanol and well-being respectively. Given the "dimmer-switch" function of endogenous CCK in the neurotransmission by 5-HT, DA, GABA, and glutamate in normal and pathological behaviors (Ballaz and Bourin, 2020), we hypothesize that CCK adjusts functioning of the reward and anxiety circuitries altered by ethanol. This review gathers data supporting this hypothesis, and suggests mechanisms underlying a role for endogenous CCK in alcoholism.
Collapse
Affiliation(s)
- Santiago Ballaz
- School of Biological Sciences & Engineering, Yachay Tech University, Hacienda San José s/n, San Miguel de Urcuquí, Ecuador; School of Medicine, Universidad Espíritu Santo, Samborondón, Ecuador.
| | - Nicole Espinosa
- School of Biological Sciences & Engineering, Yachay Tech University, Hacienda San José s/n, San Miguel de Urcuquí, Ecuador.
| | - Michel Bourin
- Neurobiology of Anxiety and Mood Disorders, University of Nantes, 98, Rue Joseph Blanchart, 44100 Nantes, France.
| |
Collapse
|
4
|
Campbell EJ, Jin S, Lawrence AJ. Environmental enrichment reduces the propensity to relapse following punishment-imposed abstinence of alcohol seeking. Physiol Behav 2019; 210:112638. [DOI: 10.1016/j.physbeh.2019.112638] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/11/2019] [Accepted: 07/31/2019] [Indexed: 02/06/2023]
|
5
|
Camarini R, Marianno P, Rae M. Social Factors in Ethanol Sensitization. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2018; 140:53-80. [PMID: 30193709 DOI: 10.1016/bs.irn.2018.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Behavioral sensitization is a neuroadaptive process characterized by an increase in a particular behavior after repeated exposure to drugs or other stimuli, such as stress. Sensitization can also be extended to neurochemical and neuroendocrine sensitization. Several factors can influence sensitization to the effects of ethanol. For instance, stress is an important component in addiction that can strengthen ethanol-induced behaviors. In animal models, stressful situations can be induced by alterations in social aspects of the animal's environment, such as maternal separation, social conflicts, and housing conditions. Social conflict models involve acute, chronic or intermittent interaction of an animal to a conspecific and can occur at any stage of life, including preweaning, adolescence or adulthood. These events can influence ethanol-induced behavioral sensitization in different ways, such as increases in locomotion, drug reward, and drug-taking behaviors. On the other hand, environmental enrichment can produce a protective phenotype against drug-related behaviors. In this chapter, we discuss findings regarding consequences of social stress and environmental enrichment on sensitization to ethanol.
Collapse
Affiliation(s)
- Rosana Camarini
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, SP, Brazil.
| | - Priscila Marianno
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, SP, Brazil
| | - Mariana Rae
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, SP, Brazil
| |
Collapse
|
6
|
Novel approaches to alcohol rehabilitation: Modification of stress-responsive brain regions through environmental enrichment. Neuropharmacology 2018; 145:25-36. [PMID: 29477298 DOI: 10.1016/j.neuropharm.2018.02.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 02/05/2018] [Accepted: 02/21/2018] [Indexed: 01/08/2023]
Abstract
Relapse remains the most prominent hurdle to successful rehabilitation from alcoholism. The neural mechanisms underlying relapse are complex, but our understanding of the brain regions involved, the anatomical circuitry and the modulation of specific nuclei in the context of stress and cue-induced relapse have improved significantly in recent years. In particular, stress is now recognised as a significant trigger for relapse, adding to the well-established impact of chronic stress to escalate alcohol consumption. It is therefore unsurprising that the stress-responsive regions of the brain have also been implicated in alcohol relapse, such as the nucleus accumbens, amygdala and the hypothalamus. Environmental enrichment is a robust experimental paradigm which provides a non-pharmacological tool to alter stress response and, separately, alcohol-seeking behaviour and symptoms of withdrawal. In this review, we examine and consolidate the preclinical evidence that alcohol seeking behaviour and stress-induced relapse are modulated by environmental enrichment, and these are primarily mediated by modification of neural activity within the key nodes of the addiction circuitry. Finally, we discuss the limited clinical evidence that stress-reducing approaches such as mindfulness could potentially serve as adjunctive therapy in the treatment of alcoholism. This article is part of the Special Issue entitled "Neurobiology of Environmental Enrichment".
Collapse
|
7
|
Beloate LN, Coolen LM. Influences of social reward experience on behavioral responses to drugs of abuse: Review of shared and divergent neural plasticity mechanisms for sexual reward and drugs of abuse. Neurosci Biobehav Rev 2017; 83:356-372. [DOI: 10.1016/j.neubiorev.2017.10.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 10/13/2017] [Accepted: 10/17/2017] [Indexed: 10/25/2022]
|
8
|
Quadir SG, Guzelian E, Palmer MA, Martin DL, Kim J, Szumlinski KK. Complex interactions between the subject factors of biological sex and prior histories of binge-drinking and unpredictable stress influence behavioral sensitivity to alcohol and alcohol intake. Physiol Behav 2017; 203:100-112. [PMID: 28803118 DOI: 10.1016/j.physbeh.2017.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 08/08/2017] [Indexed: 11/28/2022]
Abstract
Alcohol use disorders, affective disorders and their comorbidity are sexually dimorphic in humans. However, it is difficult to disentangle the interactions between subject factors influencing alcohol sensitivity in studies of humans. Herein, we combined murine models of unpredictable, chronic, mild stress (UCMS) and voluntary binge-drinking to examine for sex differences in the interactions between prior histories of excessive ethanol-drinking and stress upon ethanol-induced changes in motor behavior and subsequent drinking. In Experiment 1, female mice were insensitive to the UCMS-induced increase in ethanol-induced locomotion and ethanol intake under continuous alcohol-access. Experiment 2 revealed interactions between ethanol dose and sex (females>males), binge-drinking history (water>ethanol), and UCMS history (UCMS>controls), with no additive effect of a sequential prior history of both binge drinking and UCMS observed. We also observed an interaction between UCMS history and sex for righting recovery. UCMS history potentiated subsequent binge-drinking in water controls of both sexes and in male binge-drinking mice. Conversely, a prior binge-drinking history increased subsequent ethanol intake in females only, irrespective of prior UCMS history. In Experiment 3, a concurrent history of binge-drinking and UCMS did not alter ethanol intake, nor did it influence the ethanol dose-locomotor response function, but it did augment alcohol-induced sedation and reduced subsequent alcohol intake over that produced by binge-drinking alone. Thus, the subject factors of biological sex, prior stressor history and prior binge-drinking history interact in complex ways in mice to impact sensitivity to alcohol's motor-stimulating, -incoordinating and intoxicating effects, as well as to influence subsequent heavy drinking.
Collapse
Affiliation(s)
- Sema G Quadir
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Eugenie Guzelian
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Mason A Palmer
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Douglas L Martin
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Jennifer Kim
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Karen K Szumlinski
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA; Department of Molecular, Developmental and Cell Biology, Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA, USA.
| |
Collapse
|
9
|
Holgate JY, Garcia H, Chatterjee S, Bartlett SE. Social and environmental enrichment has different effects on ethanol and sucrose consumption in mice. Brain Behav 2017; 7:e00767. [PMID: 28828224 PMCID: PMC5561324 DOI: 10.1002/brb3.767] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 05/22/2017] [Accepted: 06/12/2017] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Factors leading to the harmful consumption of substances, like alcohol and sucrose, involve a complex interaction of genes and the environment. While we cannot control the genes we inherit, we can modify our environment. Understanding the role that social and environmental experiences play in alcohol and sucrose consumption is critical for developing preventative interventions and treatments for alcohol use disorders and obesity. METHODS We used the drinking in the dark two-bottle choice (2BC) model of ethanol and sucrose consumption to compare male C57BL/6 mice housed in the IntelliCage (an automated device capable of simultaneously measuring behaviors of up to 16 mice living in an enriched social environment) with mice housed in standard isolated and social environments. RESULTS Consistent with previous publications on ethanol-naïve and -experienced mice, social and environmental enrichment reduced ethanol preference. Isolated mice had the highest ethanol preference and IntelliCage mice the least, regardless of prior ethanol experience. In mice with no prior sucrose experience, the addition of social and environmental enrichment increased sucrose preference. However, moving isolated mice to enriched conditions did not affect sucrose preference in sucrose-experienced mice. CONCLUSIONS The impact of social and environmental enrichment on ethanol consumption differs from sucrose consumption suggesting that interventions and treatments developed for alcohol use disorders may not be suitable for sucrose consumption disorders.
Collapse
Affiliation(s)
- Joan Y Holgate
- Institute of Health and Medical Innovation Translational Research Institute Queensland University of Technology Woolloongabba QLD Australia.,Ernest Gallo Clinical and Research Center University of California San Francisco CA USA
| | - Hilary Garcia
- Ernest Gallo Clinical and Research Center University of California San Francisco CA USA
| | - Susmita Chatterjee
- Ernest Gallo Clinical and Research Center University of California San Francisco CA USA
| | - Selena E Bartlett
- Institute of Health and Medical Innovation Translational Research Institute Queensland University of Technology Woolloongabba QLD Australia.,Ernest Gallo Clinical and Research Center University of California San Francisco CA USA
| |
Collapse
|
10
|
Chronic social instability increases anxiety-like behavior and ethanol preference in male Long Evans rats. Physiol Behav 2017; 173:179-187. [DOI: 10.1016/j.physbeh.2017.02.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 02/09/2017] [Accepted: 02/10/2017] [Indexed: 01/28/2023]
|
11
|
Early social isolation increases persistence of alcohol-seeking behavior in alcohol-related contexts. Behav Pharmacol 2016; 27:185-91. [PMID: 26881772 DOI: 10.1097/fbp.0000000000000213] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Social conditions during rearing are well known to affect adult alcohol consumption, but few experiments have explored the effects of social conditions on behaviors that are related to alcohol dependence, such as the persistence of alcohol seeking. This study compared the effects of isolation (ISO) and interaction (INT) rearing on the persistence of alcohol-seeking behavior. Rats were trained to lever press for a solution of 10% alcohol diluted in water. They were then exposed to a two-component multiple schedule of reinforcement (baseline). Responses in one component were reinforced by a higher rate of alcohol delivery (rich component, variable interval 15 s) and responses in the other component were reinforced by a lower rate of delivery (lean component, variable interval 45 s). The persistence of lever pressing in the presence of each stimulus was then assessed during extinction. The results from baseline showed that response rates in rats in both groups were higher in the rich component than in the lean component, but ISO rats responded significantly more than INT rats in both components. The persistence of responding during extinction in ISO rats in both components was also higher than that in INT rats. The results show that effects of ISO are not restricted to alcohol consumption, but also affect persistence of alcohol-seeking behavior, which may reflect differences in the value of drug-related stimuli.
Collapse
|
12
|
Ng E, Browne CJ, Samsom JN, Wong AHC. Depression and substance use comorbidity: What we have learned from animal studies. THE AMERICAN JOURNAL OF DRUG AND ALCOHOL ABUSE 2016; 43:456-474. [PMID: 27315335 DOI: 10.1080/00952990.2016.1183020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Depression and substance use disorders are often comorbid, but the reasons for this are unclear. In human studies, it is difficult to determine how one disorder may affect predisposition to the other and what the underlying mechanisms might be. Instead, animal studies allow experimental induction of behaviors relevant to depression and drug-taking, and permit direct interrogation of changes to neural circuits and molecular pathways. While this field is still new, here we review animal studies that investigate whether depression-like states increase vulnerability to drug-taking behaviors. Since chronic psychosocial stress can precipitate or predispose to depression in humans, we review studies that use psychosocial stressors to produce depression-like phenotypes in animals. Specifically, we describe how postweaning isolation stress, repeated social defeat stress, and chronic mild (or unpredictable) stress affect behaviors relevant to substance abuse, especially operant self-administration. Potential brain changes mediating these effects are also discussed where available, with an emphasis on mesocorticolimbic dopamine circuits. Postweaning isolation stress and repeated social defeat generally increase acquisition or maintenance of drug self-administration, and alter dopamine sensitivity in various brain regions. However, the effects of chronic mild stress on drug-taking have been much less studied. Future studies should consider standardizing stress-induction protocols, including female subjects, and using multi-hit models (e.g. genetic vulnerabilities and environmental stress).
Collapse
Affiliation(s)
- Enoch Ng
- a Lunenfeld-Tanenbaum Research Institute , Mount Sinai Hospital , Toronto , Canada.,b Institute of Medical Science, University of Toronto , Toronto , Canada
| | - Caleb J Browne
- c Department of Psychology , University of Toronto , Toronto , Canada.,d Campbell Family Health Institute , Centre for Addiction and Mental Health , Toronto , Canada
| | - James N Samsom
- d Campbell Family Health Institute , Centre for Addiction and Mental Health , Toronto , Canada.,e Department of Pharmacology , University of Toronto , Toronto , Canada
| | - Albert H C Wong
- b Institute of Medical Science, University of Toronto , Toronto , Canada.,d Campbell Family Health Institute , Centre for Addiction and Mental Health , Toronto , Canada.,e Department of Pharmacology , University of Toronto , Toronto , Canada.,f Department of Psychiatry , University of Toronto , Toronto , Canada
| |
Collapse
|
13
|
Abstract
There is a considerable degree of individual vulnerability for alcohol use disorder (AUD) as only a subpopulation of individuals who regularly consume alcohol develop AUD. It is therefore very important to understand the factors and mechanisms that contribute towards the individual risk for AUD. In this respect, social influences, in particular during development, may be relevant for AUD as disruptions in early social experiences are associated with an increased risk for AUD. Social play, the most prominent form of social behaviour shown by young mammals, is rewarding and considered to be important for social, emotional and cognitive development. Recent studies suggest that early social isolation, effectively depriving animals from social play, increases the risk for addictive behaviour. The aim of this study was therefore to explore the long-term consequences of early social isolation on alcohol consumption and motivation for alcohol. To this end, rats were socially isolated from postnatal days 21-42, followed by 4 weeks of social housing, and voluntary alcohol consumption and operant responding for alcohol were determined in adulthood. We observed enhanced levels of alcohol consumption in adulthood in previously isolated rats, whereas operant responding for alcohol was not altered. The impact of early social isolation was independent of the individual variation in alcohol consumption. These data indicate that social isolation, during a developmental period when social play is highly abundant, enhances the propensity to consume alcohol in adulthood. This implies that early social experience may be a protective factor against excessive alcohol use.
Collapse
|
14
|
Butler TR, Karkhanis AN, Jones SR, Weiner JL. Adolescent Social Isolation as a Model of Heightened Vulnerability to Comorbid Alcoholism and Anxiety Disorders. Alcohol Clin Exp Res 2016; 40:1202-14. [PMID: 27154240 DOI: 10.1111/acer.13075] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 03/24/2016] [Indexed: 01/01/2023]
Abstract
Individuals diagnosed with anxiety-related illnesses are at increased risk of developing alcoholism, exhibit a telescoped progression of this disease and fare worse in recovery, relative to alcoholics that do not suffer from a comorbid anxiety disorder. Similarly, preclinical evidence supports the notion that stress and anxiety represent major risk factors for the development of alcohol use disorder (AUD). Despite the importance of understanding the link between anxiety and alcoholism, much remains unknown about the neurobiological substrates underlying this relationship. One stumbling block has been the lack of animal models that reliably reproduce the spectrum of behaviors associated with increased vulnerability to these diseases. Here, we review the literature that has examined the behavioral and neurobiological outcomes of a simple rodent adolescent social isolation procedure and discuss its validity as a model of vulnerability to comorbid anxiety disorders and alcoholism. Recent studies have provided strong evidence that adolescent social isolation of male rats leads to the expression of a variety of behaviors linked with increased vulnerability to anxiety and/or AUD, including deficits in sensory gating and fear extinction, and increases in anxiety measures and ethanol drinking. Neurobiological studies are beginning to identify mesolimbic adaptations that may contribute to the behavioral phenotype engendered by this model. Some of these changes include increased excitability of ventral tegmental area dopamine neurons and pyramidal cells in the basolateral amygdala and significant alterations in baseline and stimulated catecholamine signaling. A growing body of evidence suggests that adolescent social isolation may represent a reliable rodent model of heightened vulnerability to anxiety disorders and alcoholism in male rats. These studies provide initial support for the face, construct, and predictive validity of this model and highlight its utility in identifying neurobiological adaptations associated with increased risk of developing these disorders.
Collapse
Affiliation(s)
- Tracy R Butler
- Department of Psychology , University of Dayton, Dayton, Ohio
| | - Anushree N Karkhanis
- Department of Physiology and Pharmacology , Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Sara R Jones
- Department of Physiology and Pharmacology , Wake Forest School of Medicine, Winston Salem, North Carolina
| | - Jeffrey L Weiner
- Department of Physiology and Pharmacology , Wake Forest School of Medicine, Winston Salem, North Carolina
| |
Collapse
|
15
|
Alterations of reward mechanisms in bulbectomised rats. Behav Brain Res 2015; 286:271-7. [DOI: 10.1016/j.bbr.2015.03.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 03/02/2015] [Accepted: 03/06/2015] [Indexed: 01/17/2023]
|
16
|
Gill KE, Chappell AM, Beveridge TJR, Porrino LJ, Weiner JL. Chronic methylphenidate treatment during early life is associated with greater ethanol intake in socially isolated rats. Alcohol Clin Exp Res 2015; 38:2260-8. [PMID: 25156616 DOI: 10.1111/acer.12489] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 04/28/2014] [Indexed: 01/17/2023]
Abstract
BACKGROUND Methylphenidate (MPH) is a stimulant prescribed to treat attention-deficit/ hyperactivity disorder. Its primary mechanism of action is in the dopamine system, alterations of which are associated with vulnerability to alcohol abuse. There are concerns that juvenile MPH treatment may influence adult drinking behavior. This study examined the interaction of MPH treatment and environmental rearing conditions, which are known to independently influence ethanol (EtOH) drinking behavior, on anxiety-like behavior and vulnerability to alcohol abuse in a juvenile rodent model. METHODS Male Sprague-Dawley rats were housed in enriched, standard, or isolated conditions for 4 weeks, starting at postnatal day 21. Rats were concurrently treated with 8 mg/kg/d MPH or saline, delivered via osmotic minipump. Anxiety-like behavior was determined at the end of the treatment session, and 5 weeks later. After MPH treatment, rats were exposed to a 2-bottle choice EtOH drinking procedure that lasted 3 weeks. RESULTS Early life chronic MPH treatment was associated with greater EtOH intake and greater EtOH preference, but only in socially isolated animals. Isolated animals had greater levels of anxiety-like behavior than standard-housed or enriched animals after 4 weeks of exposure to the housing conditions, a difference that persisted even after all animals had been individually housed for an additional 5 weeks and exposed to EtOH. CONCLUSIONS These results suggest that early life MPH treatment may increase vulnerability to EtOH drinking in adulthood in a subset of the population. Additionally, this study highlights the importance of early rearing condition for establishing long-lasting behavioral phenotypes. Environmental histories should be considered when prescribing MPH treatment to young children.
Collapse
Affiliation(s)
- Kathryn E Gill
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston Salem, North Carolina
| | | | | | | | | |
Collapse
|
17
|
Moriya Y, Kasahara Y, Hall FS, Sakakibara Y, Uhl GR, Tomita H, Sora I. Sex differences in the effects of adolescent social deprivation on alcohol consumption in μ-opioid receptor knockout mice. Psychopharmacology (Berl) 2015; 232:1471-82. [PMID: 25363463 DOI: 10.1007/s00213-014-3784-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 10/18/2014] [Indexed: 12/29/2022]
Abstract
RATIONALE Evidence based on clinical and experimental animal studies indicates that adolescent social deprivation influences alcohol consumption in a sex-dependent manner, perhaps by influencing stress responses. However, the mechanisms underlying the interaction between these phenomena remain to be elucidated. Since the μ-opioid receptor (MOP) has been reported to have key roles in social stress responses as well as the reinforcing/addictive effects of ethanol, MOP is a candidate molecule that may link adolescent social deprivation and subsequent alterations in alcohol consumption. OBJECTIVES To evaluate the involvement of MOP and social isolation-induced changes in alcohol consumption, as well as the effect of sex differences on responses to social isolation, alcohol consumption was assessed using a two-bottle home-cage consumption procedure (8 % ethanol vs. water) in MOP knockout (MOP-KO) and wild type (WT) mice of both sexes exposed to adolescent social deprivation or reared socially. RESULTS Isolation rearing had no effects upon alcohol consumption of WT mice, whereas it significantly altered alcohol consumption in both male and female MOP-KO mice. Interestingly, social isolation affected ethanol consumption differently in male and female mice. Ethanol consumption was increased in male MOP-KO mice, but decreased in female MOP-KO mice, by isolation rearing. CONCLUSION These results indicate that disturbances of MOP function influence the effects of isolation rearing on ethanol consumption in a sex-dependent manner. Consequently, this suggests the possibility that genetic variation that influences MOP function may have differential roles in alcoholism in men and women, and alcoholism treatments that target MOP function may be differentially effective in males and females.
Collapse
Affiliation(s)
- Yuki Moriya
- Department of Biological Psychiatry, Tohoku University, Sendai, Japan
| | | | | | | | | | | | | |
Collapse
|
18
|
Knockdown of CRF1 receptors in the ventral tegmental area attenuates cue- and acute food deprivation stress-induced cocaine seeking in mice. J Neurosci 2014; 34:11560-70. [PMID: 25164654 DOI: 10.1523/jneurosci.4763-12.2014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Corticotrophin-releasing factor (CRF) modulates the influence of stress on cocaine reward and reward seeking acting at multiple sites, including the ventral tegmental area (VTA). There is controversy, however, concerning the contribution of CRF receptor type 1 (CRFR1) to this effect and whether CRF within the VTA is involved in other aspects of reward seeking independent of acute stress. Here we examine the role of CRFR1 within the VTA in relation to cocaine and natural reward using viral delivery of short hairpin RNAs (lenti-shCRFR1) and investigate the effect on operant self-administration and motivation to self-administer, as well as stress- and cue-induced reward seeking in mice. While knockdown of CRFR1 in the VTA had no effect on self-administration behavior for either cocaine or sucrose, it effectively blocked acute food deprivation stress-induced reinstatement of cocaine seeking. We also observed reduced cue-induced cocaine seeking assessed in a single extinction session after extended abstinence, but cue-induced sucrose seeking was unaffected, suggesting dissociation between the contribution of CRFR1 in the VTA in cocaine reward and sucrose and cocaine seeking. Further, our data indicate a role for VTA CRFR1 signaling in cocaine seeking associated with, and independent of, stress potentially involving conditioning and/or salience attribution of cocaine reward-related cues. CRFR1 signaling in the VTA therefore presents a target for convergent effects of both cue- and stress-induced cocaine-seeking pathways.
Collapse
|
19
|
The effects of rearing environment and chronic methylphenidate administration on behavior and dopamine receptors in adolescent rats. Brain Res 2013; 1527:67-78. [PMID: 23806775 DOI: 10.1016/j.brainres.2013.06.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 06/13/2013] [Accepted: 06/17/2013] [Indexed: 12/17/2022]
Abstract
Rearing young rodents in socially isolated or environmentally enriched conditions has been shown to affect numerous components of the dopamine system as well as behavior. Methylphenidate (MPH), a commonly used dopaminergic agent, may affect animals differently based on rearing environment. Here we examined the interaction between environment and chronic MPH treatment at clinically relevant doses, administered via osmotic minipump. Young Sprague Dawley rats (PND 21) were assigned to environmentally enriched, pair-housed, or socially isolated rearing conditions, and treated with either 0, 2, 4, or 8 mg/kg/day MPH for 3 weeks. At the end of the treatment period, animals were tested for locomotor activity and anxiety-like behavior. The densities of D1-like and D2-like receptors were measured in the striatum using in vitro receptor autoradiography. Locomotor activity and anxiety-like behavior were increased in isolated animals compared to pair-housed and enriched animals. The density of D1-like receptors was greater in isolated animals, but there were no differences between groups in D2-like receptor density. Finally, there were no effects of MPH administration on any reported measure. This study provides evidence for an effect of early rearing environment on the dopamine system and behavior, and also suggests that MPH administration may not have long-term consequences.
Collapse
|
20
|
Neisewander J, Peartree N, Pentkowski N. Emotional valence and context of social influences on drug abuse-related behavior in animal models of social stress and prosocial interaction. Psychopharmacology (Berl) 2012; 224:33-56. [PMID: 22955569 PMCID: PMC4071609 DOI: 10.1007/s00213-012-2853-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Accepted: 08/18/2012] [Indexed: 02/07/2023]
Abstract
RATIONALE Social factors are important determinants of drug dependence and relapse. OBJECTIVES We reviewed pre-clinical literature examining the role of social experiences from early life through the development of drug dependence and relapse, emphasizing two aspects of these experiences: (1) whether the social interaction is appetitive or aversive and (2) whether the social interaction occurs within or outside of the drug-taking context. METHODS The models reviewed include neonatal care, isolation, social defeat, chronic subordination, and prosocial interactions. We review results from these models in regard to effects on self-administration and conditioned place preference established with alcohol, psychostimulants, and opiates. RESULTS We suggest that in general, when the interactions occur outside of the drug-taking context, prosocial interactions are protective against drug abuse-related behaviors, whereas social stressors facilitate these behaviors. By contrast, positive or negative social interactions occurring within the drug-taking context may interact with other risk factors to enhance or inhibit these behaviors. CONCLUSIONS Despite differences in the nature and complexity of human social behavior compared to other species, the evolving animal literature provides useful models for understanding social influences on drug abuse-related behavior that will allow for research on the behavioral and biological mechanisms involved. The models have contributed to understanding social influences on initiation and maintenance of drug use, but more research is needed to understand social influences on drug relapse.
Collapse
Affiliation(s)
- J.L. Neisewander
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287-4501,Corresponding author: Janet Neisewander, Ph.D., School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287-4501, , Phone: 480-965-0209, Fax: 480-965-6899
| | - N.A. Peartree
- Department of Psychology, Arizona State University, PO Box 871104, Tempe, AZ 85287-1104
| | - N.S. Pentkowski
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287-4501
| |
Collapse
|
21
|
Chappell AM, Carter E, McCool BA, Weiner JL. Adolescent rearing conditions influence the relationship between initial anxiety-like behavior and ethanol drinking in male Long Evans rats. Alcohol Clin Exp Res 2012; 37 Suppl 1:E394-403. [PMID: 22924742 DOI: 10.1111/j.1530-0277.2012.01926.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 06/21/2012] [Indexed: 01/25/2023]
Abstract
BACKGROUND Rodent studies have demonstrated that adolescent social isolation results in many behavioral perturbations, including increases in anxiety-like behaviors. Socially isolated (SI) rats have also been shown to self-administer greater amounts ethanol (EtOH) in some, but not all, studies. Here, we tested whether juvenile social isolation increases EtOH drinking using an intermittent procedure that engenders relatively high intake in normally reared animals. We also compared the behavioral phenotype of rats reared under social isolation or group-housed conditions with adult rats housed under conditions commonly used in EtOH-drinking studies. METHODS Male Long Evans rats were procured immediately postweaning and were group housed for 1 week. Subjects were then randomly divided into 2 groups: SI rats, housed individually for 6 weeks and group-housed (GH) rats (4/cage). A third group was procured as young adults and was housed individually upon arrival for 1 week (standard housing condition). Rats were then tested in a plus-maze and novelty assay, and then, all subjects were singly housed and EtOH drinking was assessed. RESULTS SI rats displayed increased anxiety-like behaviors on the plus-maze, a greater locomotor response to a novel environment, and increased EtOH intake, relative to GH rats. Age-matched standard housed (STD) rats exhibited an anxiety-like behavioral profile on the plus-maze that was similar to SI, and not GH rats, and also drank EtOH at levels comparable with SI subjects. In addition, anxiety-like behavior on the plus-maze correlated with intermittent EtOH intake in SI and GH rats. CONCLUSIONS These data further support the validity of the rodent juvenile social isolation model for studies directed at elucidating behavioral and neurobiological mechanisms linking anxiety and EtOH drinking. These findings further suggest that housing conditions commonly employed in rodent drinking studies may recapitulate the anxiety-like and EtOH-drinking phenotype engendered by a juvenile social isolation procedure.
Collapse
Affiliation(s)
- Ann M Chappell
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
| | | | | | | |
Collapse
|
22
|
Becker HC, Lopez MF, Doremus-Fitzwater TL. Effects of stress on alcohol drinking: a review of animal studies. Psychopharmacology (Berl) 2011; 218:131-56. [PMID: 21850445 PMCID: PMC3247761 DOI: 10.1007/s00213-011-2443-9] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 08/02/2011] [Indexed: 11/26/2022]
Abstract
RATIONALE While stress is often proposed to play a significant role in influencing alcohol consumption, the relationship between stress and alcohol is complex and poorly understood. Over several decades, stress effects on alcohol drinking have been studied using a variety of animal models and experimental procedures, yet this large body of literature has generally produced equivocal results. OBJECTIVES This paper reviews results from animal studies in which alcohol consumption is evaluated under conditions of acute/sub-chronic stress exposure or models of chronic stress exposure. Evidence also is presented indicating that chronic intermittent alcohol exposure serves as a stressor that consequently influences drinking. RESULTS The effects of various acute/sub-chronic stress procedures on alcohol consumption have generally been mixed, but most study outcomes suggest either no effect or decreased alcohol consumption. In contrast, most studies indicate that chronic stress, especially when administered early in development, results in elevated drinking later in adulthood. Chronic alcohol exposure constitutes a potent stressor itself, and models of chronic intermittent alcohol exposure reliably produce escalation of voluntary alcohol consumption. CONCLUSIONS A complex and dynamic interplay among a wide array of genetic, biological, and environmental factors govern stress responses, regulation of alcohol drinking, and the circumstances in which stress modulates alcohol consumption. Suggestions for future directions and new approaches are presented that may aid in developing more sensitive and valid animal models that not only better mimic the clinical situation, but also provide greater understanding of mechanisms that underlie the complexity of stress effects on alcohol drinking.
Collapse
Affiliation(s)
- Howard C Becker
- Department of Psychiatry and Behavioral Sciences, Charleston Alcohol Research Center, Center for Drug and Alcohol Programs, 67 President Street, MSC 861, Charleston, SC 29425, USA.
| | | | | |
Collapse
|
23
|
Sarnyai Z, Alsaif M, Bahn S, Ernst A, Guest PC, Hradetzky E, Kluge W, Stelzhammer V, Wesseling H. Behavioral and molecular biomarkers in translational animal models for neuropsychiatric disorders. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 101:203-38. [PMID: 22050853 DOI: 10.1016/b978-0-12-387718-5.00008-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Modeling neuropsychiatric disorders in animals poses a significant challenge due to the subjective nature of diverse often overlapping symptoms, lack of objective biomarkers and diagnostics, and the rudimentary understanding of the pathophysiology. Successful translational research requires animal models that can inform about disease mechanisms and therapeutic targets. Here, we review behavioral and neurobiological findings from selected animal models, based on presumed etiology and risk factors, for schizophrenia, bipolar disorder, and major depressive disorder. We focus on the use of appropriate statistical tools and newly developed Research Domain Criteria (RDoC) to link biomarkers from animal models with the human disease. We argue that this approach will lead to development of only the most robust animal models for specific psychiatric disorders and may ultimately lead to better understanding of the pathophysiology and identification of novel biomarkers and therapeutic targets.
Collapse
Affiliation(s)
- Zoltán Sarnyai
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Priprem A, Chonpathompikunlert P, Sutthiparinyanont S, Wattanathorn J. Antidepressant and cognitive activities of intranasal piperine-encapsulated liposomes. ACTA ACUST UNITED AC 2011. [DOI: 10.4236/abb.2011.22017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
25
|
Smith JE, Co C, McIntosh S, Cunningham CC. Chronic binge-like moderate ethanol drinking in rats results in widespread decreases in brain serotonin, dopamine, and norepinephrine turnover rates reversed by ethanol intake. J Neurochem 2010; 105:2134-55. [PMID: 18284613 DOI: 10.1111/j.1471-4159.2008.05296.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This research was initiated to assess the turnover rates (TORs) of dopamine (DA), norepinephrine (NA), serotonin (5-HT), aspartate, glutamate, and GABA in brain regions during rodent ethanol/sucrose (EtOH) and sucrose (SUC) drinking and in animals with a history of EtOH or SUC drinking to further characterize the neuronal systems that underlie compulsive consumption. Groups of five male rats were used, with two trained to drink EtOH solutions, two to drink SUC and one to serve as a non-drinking control. When stable drinking patterns were obtained, rats were pulse labeled intravenously and killed 60 or 90 min later and the TORs of DA, norepinephrine, 5-HT, aspartate, glutamate, and GABA determined in brain regions. Changes in the TOR of 5-HT, DA, and NA were detected specific to EtOH drinking, SUC drinking or a history of EtOH or SUC drinking. An acute EtOH deprivation effect was detected that was mostly reversed with EtOH drinking. These results suggest that binge-like drinking of moderate amounts of EtOH produces a deficit in neuronal function that could set the stage for the alleviation of anhedonic stimuli with further EtOH intake that strengthen EtOH seeking behaviors which may contribute to increased EtOH use in at risk individuals.
Collapse
Affiliation(s)
- James E Smith
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1083, USA.
| | | | | | | |
Collapse
|
26
|
Anacker AMJ, Ryabinin AE. Biological contribution to social influences on alcohol drinking: evidence from animal models. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2010; 7:473-93. [PMID: 20616986 PMCID: PMC2872279 DOI: 10.3390/ijerph7020473] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Accepted: 02/08/2010] [Indexed: 11/27/2022]
Abstract
Social factors have a tremendous influence on instances of heavy drinking and in turn impact public health. However, it is extremely difficult to assess whether this influence is only a cultural phenomenon or has biological underpinnings. Research in non-human primates demonstrates that the way individuals are brought up during early development affects their future predisposition for heavy drinking, and research in rats demonstrates that social isolation, crowding or low social ranking can lead to increased alcohol intake, while social defeat can decrease drinking. Neurotransmitter mechanisms contributing to these effects (i.e., serotonin, GABA, dopamine) have begun to be elucidated. However, these studies do not exclude the possibility that social effects on drinking occur through generalized stress responses to negative social environments. Alcohol intake can also be elevated in positive social situations, for example, in rats following an interaction with an intoxicated peer. Recent studies have also begun to adapt a new rodent species, the prairie vole, to study the role of social environment in alcohol drinking. Prairie voles demonstrate a high degree of social affiliation between individuals, and many of the neurochemical mechanisms involved in regulation of these social behaviors (for example, dopamine, central vasopressin and the corticotropin releasing factor system) are also known to be involved in regulation of alcohol intake. Naltrexone, an opioid receptor antagonist approved as a pharmacotherapy for alcoholic patients, has recently been shown to decrease both partner preference and alcohol preference in voles. These findings strongly suggest that mechanisms by which social factors influence drinking have biological roots, and can be studied using rapidly developing new animal models.
Collapse
Affiliation(s)
- Allison M J Anacker
- Department of Behavioral Neuroscience, Oregon Health & Science University, 3181 SW Sam Jackson Pk Rd L470, Portland, OR 97239, USA.
| | | |
Collapse
|
27
|
Associative learning during early adulthood enhances later memory retention in honeybees. PLoS One 2009; 4:e8046. [PMID: 19956575 PMCID: PMC2779852 DOI: 10.1371/journal.pone.0008046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 11/03/2009] [Indexed: 11/19/2022] Open
Abstract
Background Cognitive experiences during the early stages of life play an important role in shaping the future behavior in mammals but also in insects, in which precocious learning can directly modify behaviors later in life depending on both the timing and the rearing environment. However, whether olfactory associative learning acquired early in the adult stage of insects affect memorizing of new learning events has not been studied yet. Methodology Groups of adult honeybee workers that experienced an odor paired with a sucrose solution 5 to 8 days or 9 to 12 days after emergence were previously exposed to (i) a rewarded experience through the offering of scented food, or (ii) a non-rewarded experience with a pure volatile compound in the rearing environment. Principal Findings Early rewarded experiences (either at 1–4 or 5–8 days of adult age) enhanced retention performance in 9–12-day-conditioned bees when they were tested at 17 days of age. The highest retention levels at this age, which could not be improved with prior rewarded experiences, were found for memories established at 5–8 days of adult age. Associative memories acquired at 9–12 days of age showed a weak effect on retention for some pure pre-exposed volatile compounds; whereas the sole exposure of an odor at any younger age did not promote long-term effects on learning performance. Conclusions The associative learning events that occurred a few days after adult emergence improved memorizing in middle-aged bees. In addition, both the timing and the nature of early sensory inputs interact to enhance retention of new learning events acquired later in life, an important matter in the social life of honeybees.
Collapse
|
28
|
Deehan GA, Cain ME, Kiefer SW. Differential Rearing Conditions Alter Operant Responding for Ethanol in Outbred Rats. Alcohol Clin Exp Res 2007; 31:1692-8. [PMID: 17651466 DOI: 10.1111/j.1530-0277.2007.00466.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Differential rearing environments affect a number of behaviors displayed by rats in adulthood. For example, rats reared in an impoverished condition (IC; reared alone in hanging metal cages), social condition (SC; reared in standard shoebox cages, 2 per cage), or enriched condition (EC; reared in a large metal cage with bedding, 14 novel objects, and 10 cohorts) display clear differences in the amount of drug they consume and/or self-administer through operant responding. Animals reared in an EC consume greater amounts of ethanol compared with rats reared in an IC when provided free access, but it is not known how differential rearing conditions affect operant responding for ethanol. METHODS Twenty-eight male Long-Evans rats were reared in 1 of 3 environments (IC, SC, or EC) during postnatal days 21 to 111. At the conclusion of the rearing period, all rats underwent sucrose/ethanol fading and then were tested for lever press responding for 10% ethanol as well as ethanol preference. RESULTS Rats reared in an IC responded for 10% ethanol at significantly higher rates than SC and EC rats. A greater percentage of IC rats were able to switch lever responding when the ethanol availability was changed to a second lever. Lastly, the IC group was the only one to display a clear preference for 10% ethanol when both this fluid and water were available. CONCLUSION Rats reared in an IC show greater proclivity to respond operantly for 10% ethanol compared with rats raised in either SC or EC (which did not differ from each other). These findings agree with a number of studies that have shown isolate reared animals to consume greater amounts of ethanol compared with their socially reared counterparts yet contrast some studies showing EC animals consume greater amounts of ethanol than IC rats. The current findings illustrate that rearing environment also plays an important role in an animal's proclivity to respond for ethanol.
Collapse
Affiliation(s)
- Gerald A Deehan
- Department of Psychology, Kansas State University, Manhattan, Kansas 66506, USA.
| | | | | |
Collapse
|
29
|
Djouma E, Card K, Lodge DJ, Lawrence AJ. The CRF1 receptor antagonist, antalarmin, reverses isolation-induced up-regulation of dopamine D2 receptors in the amygdala and nucleus accumbens of fawn-hooded rats. Eur J Neurosci 2007; 23:3319-27. [PMID: 16820021 DOI: 10.1111/j.1460-9568.2006.04864.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have previously shown that Fawn-Hooded (FH) rats reared in isolation display an anxiety-like phenotype and an enhanced acquisition of ethanol seeking behaviour. Furthermore, antalarmin, a selective corticotrophin-releasing factor type 1 (CRF1) receptor antagonist, reduces isolation-induced acquisition and maintenance of volitional ethanol consumption in this strain. The aim of this study was to investigate the ability of CRF1 receptor antagonism by antalarmin to impact upon brain chemistry in both isolated and group-housed FH rats. To achieve this, FH rats were reared, from weaning, in either group-housed or isolation-housed conditions and at 12 weeks of age were treated with antalarmin (20 mg/kg, i.p; n = 10 per group) or vehicle (1 mL/kg, i.p; n = 10 per group) bi-daily for ten consecutive days before being killed and their brains removed for neurochemical analyses. Autoradiography and in situ hybridization was employed to analyse changes in the dopaminergic and neurotrophin systems. Isolation rearing increased dopamine D2 receptor density in the central amygdala and nucleus accumbens, an effect reversed by antalarmin treatment. Conversely, treatment with antalarmin had no impact upon the isolation-induced alterations of the mRNA encoding brain-derived neurotrophic factor or the TrkB receptor. Collectively, these findings demonstrate that multiple signalling systems are susceptible to modulation by social isolation and that antalarmin can reverse some, but not all, isolation-induced alterations in brain chemistry.
Collapse
Affiliation(s)
- Elvan Djouma
- Department of Pharmacology, Monash University, Clayton, Victoria 3800, Australia
| | | | | | | |
Collapse
|
30
|
Iso H, Simoda S, Matsuyama T. Environmental change during postnatal development alters behaviour, cognitions and neurogenesis of mice. Behav Brain Res 2007; 179:90-8. [PMID: 17321608 DOI: 10.1016/j.bbr.2007.01.025] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 01/04/2007] [Accepted: 01/23/2007] [Indexed: 10/23/2022]
Abstract
Four groups of male C57BL/6 mice were reared differing combinations of the two environments from 3 to 11 weeks after birth. At 12 and 13 weeks they were assessed by measures of behaviour and learning: open-field activity, auditory startle reflex and prepulse inhibition, water maze learning, and passive avoidance. Another four groups of mice reared under these varying conditions were examined for generation of neurons in hippocampus and cerebral cortex using bromodeoxyuridine (BrdU) at 12 weeks. Enriched (EE) and impoverished (PP) groups were housed in their respective environment for 8 weeks, enriched-impoverished (EP) and impoverished-enriched (PE) mice respectively were reared for 6 weeks in the first-mentioned environment and then for 2 weeks in the second. PP and EP mice showed hyperactivity, greater startle amplitude and significantly slower learning in a water maze than EE or PE animals, and also showed a memory deficit in a probe test, avoidance performance did not differ. Neural generation was greater in the EE and PE than PP and EP groups, especially in the hippocampus. These results suggest that environmental change critically affects behavioural and anatomic brain development, even if brief. In these mice, the effect of unfavourable early experience could be reversed by a later short of favourable experience.
Collapse
Affiliation(s)
- Hiroyuki Iso
- Department of Behaviour Science, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
| | | | | |
Collapse
|
31
|
Funk CK, Zorrilla EP, Lee MJ, Rice KC, Koob GF. Corticotropin-releasing factor 1 antagonists selectively reduce ethanol self-administration in ethanol-dependent rats. Biol Psychiatry 2007; 61:78-86. [PMID: 16876134 PMCID: PMC2741496 DOI: 10.1016/j.biopsych.2006.03.063] [Citation(s) in RCA: 246] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Revised: 03/09/2006] [Accepted: 03/09/2006] [Indexed: 12/27/2022]
Abstract
BACKGROUND Alcohol dependence is characterized by excessive alcohol consumption, loss of control over intake, and the presence of a withdrawal syndrome, which includes both motivational and physical symptoms. Similar to human alcoholics, ethanol-dependent animals display enhanced anxiety-like behaviors and enhanced ethanol self-administration during withdrawal, effects hypothesized to result from a dysregulation of corticotropin-releasing factor (CRF) stress systems. Here, we used an animal model of ethanol dependence to test the effects of CRF(1) receptor antagonists on excessive ethanol self-administration in dependent rats. METHODS Wistar rats, trained to orally self-administer ethanol, were exposed intermittently to ethanol vapors to induce ethanol dependence. Nondependent animals were exposed to control air. Following a 2-hour period of withdrawal, dependent and nondependent animals were systemically administered antalarmin, MJL-1-109-2, or R121919 (CRF(1) antagonists) and ethanol self-administration was measured. RESULTS The nonpeptide, small molecule CRF(1) antagonists selectively reduced excessive self-administration of ethanol in dependent animals during acute withdrawal. The antagonists had no effect on ethanol self-administration in nondependent rats. CONCLUSIONS These data demonstrate that CRF(1) receptors play an important role in mediating excessive ethanol self-administration in dependent rats, with no effect in nondependent rats. CRF(1) antagonists may be exciting new pharmacotherapeutic targets for the treatment of alcoholism in humans.
Collapse
Affiliation(s)
- Cindy K Funk
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, California 92037, USA.
| | | | | | | | | |
Collapse
|
32
|
Ago Y, Takahashi K, Nakamura S, Hashimoto H, Baba A, Matsuda T. Anxiety-Like and Exploratory Behaviors of Isolation-Reared Mice in the Staircase Test. J Pharmacol Sci 2007; 104:153-8. [PMID: 17538228 DOI: 10.1254/jphs.fp0070325] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The behavior of isolation-reared mice has not yet been studied in the staircase test. The present study examined the effects of anxiolytic or anxiogenic agents and isolation rearing on the behavior of ddY (outbred) strain mice in the staircase test. Diazepam and phenobarbital increased the number of steps climbed, but did not affect rearing behavior in group-reared mice. FG-7142, a benzodiazepine inverse agonist, significantly increased the number of rearing with no changes in the number of steps climbed in group-reared mice. Methamphetamine increased the number of steps climbed and decreased the number of rearing in group-reared mice. Although isolation-reared mice showed hyperactivity, there was no difference in locomotor activity for the test period of 3 min between isolation- and group-reared mice. Under these conditions, isolation rearing increased the numbers of steps climbed and rearing compared to group-reared controls. Microanalysis of locomotor patterns of group-reared mice in the staircase test showed that anxiolytic drugs increased the number of climbing to the top step of the staircase and methamphetamine increased the number of climbing to the first to third step. These results suggest that isolation rearing causes an anxiety-like state with increased exploratory behavior in mice.
Collapse
Affiliation(s)
- Yukio Ago
- Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565-0871, Japan
| | | | | | | | | | | |
Collapse
|
33
|
Reinhard C, Wolffgramm J. Long-term voluntary consumption of MDMA and THC in rats is modified by individual and situational factors. Addict Biol 2006; 11:131-44. [PMID: 16800826 DOI: 10.1111/j.1369-1600.2006.00022.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Factors influencing long-term voluntary intake of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) and Delta9-tetrahydrocannabinol (THC; cannabis) were studied in a rat model. Sixty-four male Wistar rats were given free choice for 49 weeks between (1) water and MDMA solution, (2) water and THC solution or (3) water, MDMA solution and THC solution. After the first experiences with the drugs, animals of both monodrug and polydrug group developed an individually stable pattern of MDMA consumption, whereas the individual predictability of THC consumption remained poor. While THC consumption was maintained for the whole experimental period, MDMA consumption decreased with time and was nearly ceased after 3-7 months. Intake of both drugs was adapted to social changes, with THC consumption being more sensitive to social changes than MDMA consumption. In the re-test after 4 months of abstinence, all animals ceased drug consumption when the drug solutions were adulterated with bitter tasting quinine. The results show that the rats had maintained a flexible mode of drug consumption and had not become addicted. Response to novelty of the rats in test trials before the start of drug supply correlated with later MDMA intake. In conclusion, although very low amounts of MDMA and/or THC were consumed, the findings that drug-experienced animals responded differentially to a stressor and that housing conditions influenced drug intake suggests that MDMA and THC can induce psychopharmacological effects in our long-term voluntary consumption paradigm.
Collapse
Affiliation(s)
- Carola Reinhard
- Section of Addiction Reseasrch, Department of Psychiatry, University Hospital, Tuebingen, Germany.
| | | |
Collapse
|
34
|
Thorsell A, Slawecki CJ, El Khoury A, Mathe AA, Ehlers CL. The effects of social isolation on neuropeptide Y levels, exploratory and anxiety-related behaviors in rats. Pharmacol Biochem Behav 2006; 83:28-34. [PMID: 16458953 DOI: 10.1016/j.pbb.2005.12.005] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Revised: 11/30/2005] [Accepted: 12/06/2005] [Indexed: 10/25/2022]
Abstract
NPY is one of the most abundantly expressed peptides within the CNS, and has been previously demonstrated to be altered in several animal models of depression, as well as to be differentially regulated by acute and repeated stress. The effect of social deprivation, through isolation housing, on brain NPY concentrations in adult rats has not been previously investigated. The effects of 12 weeks of social isolation, in adult rats, on anxiety-related behaviors and central concentrations of NPY in: hypothalamus, amygdala, caudate-putamen, hippocampus, and frontal cortex were evaluated. Single housed animals spent significantly more time on the open arms of the elevated plus maze and in the central area of the open field as compared to pair housed controls. These data are most likely indicative of enhanced exploration and novelty seeking. Concentrations of neuropeptide Y were increased in the caudate-putamen of the single housed subjects. NPY levels in caudate/putamen and hypothalamus were also significantly correlated with time spent in the open arms of the elevated plus maze. These data suggest that chronic social isolation, in these adult Wistar rats, did not increase anxiety but produced enhanced exploration in tests of anxiety, an effect that was associated with NPY concentrations in the striatum and hypothalamus.
Collapse
Affiliation(s)
- Annika Thorsell
- The Scripps Research Institute, Department of Neuropharmacology (CVN-14), 10550 N. Torrey Pines Rd, La Jolla, CA 92037, USA
| | | | | | | | | |
Collapse
|
35
|
Cowen MS, Djouma E, Lawrence AJ. The Metabotropic Glutamate 5 Receptor Antagonist 3-[(2-Methyl-1,3-thiazol-4-yl)ethynyl]-pyridine Reduces Ethanol Self-Administration in Multiple Strains of Alcohol-Preferring Rats and Regulates Olfactory Glutamatergic Systems. J Pharmacol Exp Ther 2005; 315:590-600. [PMID: 16014750 DOI: 10.1124/jpet.105.090449] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The metabotropic glutamate 5 receptor (mGlu5) receptor has been implicated as having a role in pain modulation, anxiety, and depression, as well as drug-seeking behavior. In the present study, we examined the effect of the selective mGlu5 receptor antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP) on operant ethanol self-administration by two strains of rats, the Fawn-Hooded (FH) rat and the inbred alcohol-preferring (iP) rat. MTEP (2 mg/kg i.p.) caused a significant reduction in responding for ethanol by both strains of rats; however, in the iP rats, MTEP also induced apparent sedation at this dose, although still reduced alcohol responding at lower doses. Chronic MTEP (2 mg/kg/day) caused a significant reduction in ethanol consumption by FH rats in a two-bottle preference test; however, chronic treatment with this dose had no effect on anxiety-like behavior or depressive-like behavior in FH rats, suggesting the dose used was subthreshold for anxiolytic or antidepressive-like effects. Finally, repeated dosing with MTEP (2 mg/kg i.p.) caused significant reductions in expression of the mRNA encoding the NR1 subunit of the N-methyl-D-aspartate receptor and the GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor in the cingulate cortex. A significant decrease in NR1 expression also occurred in the piriform cortex. Chronic MTEP also caused a significant decrease in mGlu5 gene expression and a significant increase in dopamine transporter and dopamine D(2)-like receptor binding within the olfactory tubercle. Collectively, these data suggest that MTEP can reduce alcohol-seeking behavior in different rodent models of alcoholism, and this effect is associated with regulation of cortical glutamate systems, particularly those in olfactory-related regions.
Collapse
Affiliation(s)
- Michael S Cowen
- Howard Florey Institute, Royal Parade, University of Melbourne, Victoria, Australia
| | | | | |
Collapse
|
36
|
Thorsell A, Slawecki CJ, Khoury A, Mathe AA, Ehlers CL. Effect of social isolation on ethanol consumption and substance P/neurokinin expression in Wistar rats. Alcohol 2005; 36:91-7. [PMID: 16396742 DOI: 10.1016/j.alcohol.2005.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 05/09/2005] [Accepted: 07/13/2005] [Indexed: 10/24/2022]
Abstract
Environmental factors, such as adverse life experiences and family/peer influences have a substantial influence on the development of disorders related to alcohol use. In animals, maternal or peer separation/isolation has been used as an environmental intervention that has been shown to alter neurodevelopment and influence drinking behaviors in rodents and primates. In this study, the effects of adult peer isolation on subsequent ethanol intake were investigated in Wistar rats. Because central tachykinin levels have been reported to differ between rats selected for enhanced ethanol preference, neuropeptide [neurokinin A (NKA), substance P (SP)] concentrations were also estimated. Lower levels of ethanol intake, in a two-bottle free-choice model, were observed on the first day of forced ethanol drinking in the single-housed animals. However, overall ethanol consumption was unaffected by peer isolation. Peer isolation significantly lowered SP and NKA levels in the hypothalamus, but this effect was not related to ethanol consumption or body weight. These data indicate that endogenous SP and neurokinin levels are reduced by isolation housing, but this was not associated with alterations in drinking levels using a two-bottle choice procedure.
Collapse
Affiliation(s)
- Annika Thorsell
- The Scripps Research Institute, Department of Neuropharmacology (CVN-14), 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | | | | | | | | |
Collapse
|
37
|
Lodge DJ, Roques BP, Lawrence AJ. Atypical behavioural responses to CCK-B receptor ligands in Fawn-Hooded rats. Life Sci 2003; 74:1-12. [PMID: 14575808 DOI: 10.1016/j.lfs.2003.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
At present there is an increasing literature demonstrating heterogeneity of the CCK-B receptor. Recent reports by our laboratory have demonstrated that the Fawn-Hooded rat demonstrates atypical neurochemical responses to CCK4, in vitro. Since the ability of CCK-B receptor ligands to modulate affective state is dependent on the putative receptor subtype activated, the aim of the present study was to examine the behavioural effects of the CCK-B receptor agonist, t-boc-CCK4, and the CCK-B receptor antagonist, Ci-988 in Fawn-Hooded and Wistar Kyoto rats. Interestingly, both t-boc-CCK4 and Ci-988 produced an anxiolytic profile in FH rats as determined by an increased time spent on the open arms of an elevated plus maze, while both drugs were devoid of any behavioural effect in WKY rats, lending further support to the theory that the FH rat strain has an atypical relative proportion of these putative subtypes apparently resulting in a predominantly CCK-B2 receptor effect.
Collapse
Affiliation(s)
- Daniel J Lodge
- Department of Pharmacology, Monash University, Wellington Road, Box 13E, Clayton, Victoria 3800, Australia
| | | | | |
Collapse
|
38
|
Lodge DJ, Lawrence AJ. The neurochemical effects of anxiolytic drugs are dependent on rearing conditions in Fawn-Hooded rats. Prog Neuropsychopharmacol Biol Psychiatry 2003; 27:451-8. [PMID: 12691780 DOI: 10.1016/s0278-5846(03)00032-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
There is a vast literature examining the neurochemical effects of anxiolytics throughout the rat brain; however, although the behavioural actions of anxiolytic drugs are routinely assessed in animal models of anxiety, the majority of neurochemical studies have been performed in rats with relatively 'normal' behavioural phenotypes. Since there is significant evidence that an anxious phenotype is associated with numerous neurochemical alterations, it is feasible that the central effects of anxiolytics may vary depending on the underlying behavioural state (and corresponding neuropathology) of the experimental animal. For this reason, the aim of the present study was to examine the effect of chronic anxiolytic drug administration on the central CCK and dopamine systems in anxious (isolated from weaning) and nonanxious (group-housed) Fawn-Hooded (FH) rats. It is important to note that these studies were performed in rats with continued access to ethanol, which may affect the responses to anxiolytic treatment. Chronic anxiolytic treatment with the selective CCK-B (CCK(2)) receptor antagonist, Ci-988 (0.3 mg/kg/day ip) or diazepam (2 mg/kg/day ip), induced numerous effects throughout the central nervous system (CNS), with Ci-988 inducing significant changes in the density of dopamine D(2) receptors, and diazepam producing marked changes in both dopamine D(2) and CCK-B receptor binding density as well as preproCCK mRNA expression. Interestingly, the neurochemical effects of these anxiolytic drugs varied significantly depending on the rearing conditions of the rats, demonstrating the importance of using adequate animal models when correlating the behavioural and central effects of drugs acting throughout the CNS.
Collapse
Affiliation(s)
- Daniel J Lodge
- Department of Pharmacology, Monash University, Box 13E, Clayton, Victoria 3800, Australia.
| | | |
Collapse
|