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Peart DR, Claridge EV, Karlovcec JM, El Azali R, LaDouceur KE, Sikic A, Thomas A, Stone AP, Murray JE. Generalization of a positive-feature interoceptive morphine occasion setter across the rat estrous cycle. Horm Behav 2024; 162:105541. [PMID: 38583235 DOI: 10.1016/j.yhbeh.2024.105541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 03/17/2024] [Accepted: 03/29/2024] [Indexed: 04/09/2024]
Abstract
INTRODUCTION Interoceptive stimuli elicited by drug administration acquire conditioned modulatory properties of the induction of conditioned appetitive behaviours by exteroceptive cues. This effect may be modeled using a drug discrimination task in which the drug stimulus is trained as a positive-feature (FP) occasion setter (OS) that disambiguates the relation between an exteroceptive light conditioned stimulus (CS) and a sucrose unconditioned stimulus (US). We previously reported that females are less sensitive to generalization of a FP morphine OS than males, so we investigated the role of endogenous ovarian hormones in this difference. METHODS Male and female rats received intermixed injections of 3.2 mg/kg morphine or saline before each daily training session. Training consisted of 8 presentations of the CS, each followed by access to sucrose on morphine, but not saline sessions. Following acquisiton, rats were tested for generalization of the morphine stimulus to 0, 1.0, 3.2, and 5.4 mg/kg morphine. Female rats were monitored for estrous cyclicity using vaginal cytology throughout the study. RESULTS Both sexes acquired stable drug discrimination. A gradient of generalization was measured across morphine doses and this behaviour did not differ by sex, nor did it differ across the estrous cycle in females. CONCLUSIONS Morphine generalization is independent of fluctuations in levels of sex and endogenous gonadal hormones in females under these experimental conditions.
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Affiliation(s)
- Davin R Peart
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Ella V Claridge
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Jessica M Karlovcec
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Rita El Azali
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Kathleen E LaDouceur
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Anita Sikic
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Abina Thomas
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Adiia P Stone
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada
| | - Jennifer E Murray
- Department of Psychology, University of Guelph, Guelph, ON, Canada; Collaborative Neurosciences Graduate Program, University of Guelph, Guelph, ON, Canada.
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Peart DR, Andrade AK, Logan CN, Knackstedt LA, Murray JE. Regulation of Cocaine-related Behaviors by Estrogen and Progesterone. Neurosci Biobehav Rev 2022; 135:104584. [DOI: 10.1016/j.neubiorev.2022.104584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 01/30/2022] [Accepted: 02/12/2022] [Indexed: 10/19/2022]
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Martini M, Irvin JW, Lee CG, Lynch WJ, Rissman EF. Sex chromosome complement influences vulnerability to cocaine in mice. Horm Behav 2020; 125:104821. [PMID: 32721403 PMCID: PMC7541729 DOI: 10.1016/j.yhbeh.2020.104821] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 07/19/2020] [Accepted: 07/20/2020] [Indexed: 02/08/2023]
Abstract
Women acquire cocaine habits faster and are more motivated to obtain drug than men. In general, female rodents acquire intravenous cocaine self-administration (SA) faster and show greater locomotor responses to cocaine than males. Sex differences are attributed to differences in circulating estradiol. We used the four core genotype (FCG) mouse to ask whether sex chromosome complement influences vulnerability to cocaine's reinforcing and/or locomotor-activating effects. The FCG cross produces ovary-bearing mice with XX or XY genotypes (XXF, XYF) and testes-bearing mice with XX or XY genotypes (XXM, XYM). A greater percentage of gonadal females acquired cocaine SA via infusions into jugular catheters as compared with XYM mice, but XXM mice were not significantly different than any other group. Discrimination of the active versus inactive nose poke holes and cocaine intake were in general greater in gonadal females than in gonadal males. Progressive ratio tests for motivation revealed an interaction between sex chromosomes and gonads: XYM mice were more motivated to self-administer cocaine taking more infusions than mice in any other group. Locomotor responses to cocaine exposure revealed effects of sex chromosomes. After acute exposure, activity was greater in XX than in XY mice and the reverse was true for behavioral sensitization. Mice with XY genotypes displayed more activity than XX mice when given cocaine after a 10-day drug-free period. Our data demonstrate that sex chromosome complement alone and/or interacting with gonadal status can modify cocaine's reinforcing and locomotor-activating effects. These data should inform current studies of sex differences in drug use.
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Affiliation(s)
- Mariangela Martini
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Joshua W Irvin
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Christina G Lee
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Wendy J Lynch
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia School of Medicine, Charlottesville, VA 22903, USA
| | - Emilie F Rissman
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA.
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4
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Kharas N, Yang PB, Robles T, Sanchez A, Dafny N. Sex differences in the intensity of cross-sensitization between methylphenidate and amphetamine in adolescent rats. Physiol Behav 2019; 202:77-86. [PMID: 30653974 DOI: 10.1016/j.physbeh.2018.12.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 10/27/2022]
Abstract
Chronic use of psychostimulants such as methylphenidate (MPD) and amphetamine (Amph) leads to abuse and dependence. Cross-sensitization occurs when exposure to a drug causes a significant intensified response to a different drug as compared to the effect of the drug in subjects with no previous exposure. Cross-sensitization is used as an experimental correlate for a drug's potential to elicit dependence. The present study uses male and female adolescent rats to examine whether cross-sensitization occurs with MPD, a drug not traditionally considered to elicit dependence, and Amph, a drug considered to elicit dependence. The results showed that there is cross-sensitization with MPD to Amph in adolescent rats and that there is a significant difference in male and female responses. Cross-sensitization between MPD and Amph was observed in a linear dose dependent manner in males and in an inverted U-shape pattern in females. Males treated with the highest dose of 10.0 mg/kg MPD and females treated with the mid-dose of 2.5 mg/kg MPD showed the most robust cross-sensitization. Overall, adolescent female rodents had a greater intensity of response to MPD, Amph, and cross-sensitization between MPD and Amph. This study shows that there are significant sex differences in psychostimulant cross-sensitization in adolescence, indicating the maturity of the gonadal system is not the predominant reason for differences between male and female responses to psychostimulant drugs.
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Affiliation(s)
- Natasha Kharas
- McGovern Medical School, University of Texas Health Science Center, Houston, TX 77006, United States
| | - Pamela B Yang
- Department of Biological Sciences, Chapman University, Orange, CA 92866, United States
| | - Tiffany Robles
- McGovern Medical School, University of Texas Health Science Center, Houston, TX 77006, United States
| | - Ashley Sanchez
- McGovern Medical School, University of Texas Health Science Center, Houston, TX 77006, United States
| | - Nachum Dafny
- McGovern Medical School, University of Texas Health Science Center, Houston, TX 77006, United States.
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5
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Stolf AR, Cupertino RB, Müller D, Sanvicente-Vieira B, Roman T, Vitola ES, Grevet EH, von Diemen L, Kessler FHP, Grassi-Oliveira R, Bau CHD, Rovaris DL, Pechansky F, Schuch JB. Effects of DRD2 splicing-regulatory polymorphism and DRD4 48 bp VNTR on crack cocaine addiction. J Neural Transm (Vienna) 2018; 126:193-199. [PMID: 30367264 DOI: 10.1007/s00702-018-1946-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 10/17/2018] [Indexed: 11/24/2022]
Abstract
There is evidence that dopamine receptors D2 (DRD2) and D4 (DRD4) polymorphisms may influence substance use disorders (SUD) susceptibility both individually and through their influence in the formation of DRD2-DRD4 heteromers. The dopaminergic role on the vulnerability to addiction appears to be influenced by sex. A cross-sectional study with 307 crack cocaine addicts and 770 controls was conducted. The influence of DRD2 rs2283265 and DRD4 48 bp VNTR in exon 3 variants, as well as their interaction on crack cocaine addiction susceptibility and severity were evaluated in women and men separately. An association between the DRD2 T allele and crack cocaine addiction was found in women. In this same group, interaction analysis demonstrated that the presence of DRD2-T allele and concomitant absence of DRD4-7R allele were associated with risk for crack cocaine addiction. No influence of DRD2 and DRD4 variants was observed in men regarding addiction severity. This study reinforces the role of dopaminergic genes in externalizing behaviors, especially the influence of DRD2-DRD4 interaction on SUD. This is the fourth sample that independently associated the DRD2-DRD4 interaction with SUD itself or related disorders. In addition, our findings point out to a potential difference of dopaminergic neurotransmission across sex influencing addiction susceptibility.
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Affiliation(s)
- Anderson R Stolf
- Center for Drug and Alcohol Research, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Renata B Cupertino
- Department of Genetics, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Diana Müller
- Department of Genetics, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Breno Sanvicente-Vieira
- Developmental Cognitive Neuroscience Lab (DCNL), Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
| | - Tatiana Roman
- Department of Genetics, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Eduardo S Vitola
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Eugenio H Grevet
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Lisia von Diemen
- Center for Drug and Alcohol Research, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Felix H P Kessler
- Center for Drug and Alcohol Research, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Rodrigo Grassi-Oliveira
- Developmental Cognitive Neuroscience Lab (DCNL), Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
| | - Claiton H D Bau
- Center for Drug and Alcohol Research, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
| | - Diego L Rovaris
- Department of Genetics, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Flavio Pechansky
- Center for Drug and Alcohol Research, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Jaqueline B Schuch
- Department of Genetics, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. .,Laboratory of Immunosenescence, Graduate Program in Biomedical Gerontology, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga, 6681, prédio 81, Porto Alegre, Rio Grande do Sul, CEP 90619-900, Brazil.
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6
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Jenney CB, Dasalla J, Grigson PS. Female rats exhibit less avoidance than male rats of a cocaine-, but not a morphine-paired, saccharin cue. Brain Res Bull 2017; 138:80-87. [PMID: 28899794 DOI: 10.1016/j.brainresbull.2017.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 08/29/2017] [Accepted: 09/01/2017] [Indexed: 12/12/2022]
Abstract
Rats avoid intake of an otherwise palatable taste cue when paired with drugs of abuse (Grigson and Twining, 2002). In male rats, avoidance of drug-paired taste cues is associated with conditioned blunting of dopamine in the nucleus accumbens (Grigson and Hajnal, 2007), conditioned elevation in circulating corticosterone (Gomez et al., 2000), and greater avoidance of the drug-paired cue predicts greater drug-taking (Grigson and Twining, 2002). While female rats generally are more responsive to drug than male rats, in this self-administration model, female rats consume more of a cocaine-paired saccharin cue and take less drug than males (Cason and Grigson, 2013). What is not known, however, is whether the same is true when a saccharin cue predicts availability of an opiate, particularly when the amount of drug experienced is held constant via passive administration by the experimenter. Here, avoidance of a saccharin cue was evaluated following pairings with experimenter delivered cocaine or morphine in male and female rats. Results showed that males and females avoided intake of a taste cue when paired with experimenter administered morphine or cocaine, and individual differences emerged whereby some male and female rats exhibited greater avoidance of the drug-paired cue than others. Female rats did not drink more of the saccharin cue than males when paired with morphine in Experiment 1, however, they did drink more of the saccharin cue than male rats when paired with cocaine in Experiment 2. While no pattern with estrous cycle emerged, avoidance of the cocaine-paired cue, like avoidance of a morphine-paired cue (Gomez et al., 2000), was associated with a conditioned elevation in corticosterone in both male and female rats.
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Affiliation(s)
- Christopher B Jenney
- Department of Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA 17033, United States; Nutrition and Foods Program, School of Family and Consumer Sciences, Texas State University, San Marcos, TX 78666, United States
| | - Jinju Dasalla
- Department of Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA 17033, United States
| | - Patricia S Grigson
- Department of Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA 17033, United States.
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7
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Kayyal S, Trinh T, Dafny N. Adolescent and Adult Circadian Rhythm Activity Modulated Differently Following Chronic Methylphenidate Administration. ACTA ACUST UNITED AC 2015. [DOI: 10.4236/jbbs.2015.52005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Gillies G, Virdee K, McArthur S, Dalley J. Sex-dependent diversity in ventral tegmental dopaminergic neurons and developmental programing: A molecular, cellular and behavioral analysis. Neuroscience 2014; 282:69-85. [PMID: 24943715 PMCID: PMC4245713 DOI: 10.1016/j.neuroscience.2014.05.033] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/12/2014] [Accepted: 05/18/2014] [Indexed: 02/02/2023]
Abstract
The knowledge that diverse populations of dopaminergic neurons within the ventral tegmental area (VTA) can be distinguished in terms of their molecular, electrophysiological and functional properties, as well as their differential projections to cortical and subcortical regions has significance for key brain functions, such as the regulation of motivation, working memory and sensorimotor control. Almost without exception, this understanding has evolved from landmark studies performed in the male sex. However, converging evidence from both clinical and pre-clinical studies illustrates that the structure and functioning of the VTA dopaminergic systems are intrinsically different in males and females. This may be driven by sex differences in the hormonal environment during adulthood ('activational' effects) and development (perinatal and/or pubertal 'organizational' effects), as well as genetic factors, especially the SRY gene on the Y chromosome in males, which is expressed in a sub-population of adult midbrain dopaminergic neurons. Stress and stress hormones, especially glucocorticoids, are important factors which interact with the VTA dopaminergic systems in order to achieve behavioral adaptation and enable the individual to cope with environmental change. Here, also, there is male/female diversity not only during adulthood, but also in early life when neurobiological programing by stress or glucocorticoid exposure differentially impacts dopaminergic developmental trajectories in male and female brains. This may have enduring consequences for individual resilience or susceptibility to pathophysiological change induced by stressors in later life, with potential translational significance for sex bias commonly found in disorders involving dysfunction of the mesocorticolimbic dopaminergic systems. These findings highlight the urgent need for a better understanding of the sexual dimorphism in the VTA if we are to improve strategies for the prevention and treatment of debilitating conditions which differentially affect men and women in their prevalence and nature, including schizophrenia, attention/deficit hyperactivity disorder, autism spectrum disorders, anxiety, depression and addiction.
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Affiliation(s)
- G.E. Gillies
- Division of Brain Sciences, Imperial College London, Hammersmith Hospital, London, UK,Corresponding author. Address: Division of Brain Sciences, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK. Tel: +44-(0)-20-7594-7050.
| | - K. Virdee
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK,Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK
| | - S. McArthur
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1 6BQ, UK
| | - J.W. Dalley
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK,Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK,Department of Psychiatry, University of Cambridge, Addenbrooke’s Hospital, Hill’s Road, Cambridge CB2 2QQ, UK
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9
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Cholanian M, Lobzova A, Das B, Yelleswarapu C, Donaldson ST. Digital holographic microscopy discriminates sex differences in medial prefrontal cortex GABA neurons following amphetamine sensitization. Pharmacol Biochem Behav 2014; 124:326-32. [PMID: 24999221 DOI: 10.1016/j.pbb.2014.06.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Revised: 06/09/2014] [Accepted: 06/27/2014] [Indexed: 11/27/2022]
Abstract
Sex differences have been noted in patterns of drug use and relapse, and in particular with amphetamine abuse, implicating estradiol in mediating female neurobehavioral responses. To investigate the interaction of estradiol with amphetamine-induced hyperactivity, we compared male, intact female (INTACT), ovariectomized (OVX) and ovariectomized estradiol-treated (OVX+EB) female rats receiving repeated amphetamine (AMPH) treatment. All rats received intermittent AMPH injections for three days, and baseline and post-injection locomotor activity as well as fine-motor movements were recorded. Upon completion of behavioral experiments, immunohistochemistry was performed to assess parvalbumin-immunoreactive (PV-IR) GABAergic neurons in the medial prefrontal cortex (mPFC). Results indicate that AMPH induced greater behavioral response during habituation among the INTACT animals, and post-injection hyperactivity was apparent on days 2 and 3, among INTACT and OVX+EB females. For INTACT animals, the hyperactivity was most pronounced when estrogen levels were high. Immunohistochemical analysis using digital holographic microscopy revealed INTACT and OVX+EB females had less expression and smaller somatic area of PV-IR neurons in the mPFC. These data provide evidence for rapid development of sex differences in response to AMPH that correlates with sexually dimorphic alterations in a subset of mPFC GABAergic neurons implicated in modulating forebrain dopamine projections.
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Affiliation(s)
- Marina Cholanian
- Department of Physiology, University of Arizona College of Medicine, Tucson, AZ 85724, USA
| | - Anna Lobzova
- Touro College of Osteopathic Medicine, New York, NY 10027, USA
| | - Bhargab Das
- Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Chandra Yelleswarapu
- Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA
| | - S Tiffany Donaldson
- Department of Psychology, University of Massachusetts Boston, Boston, MA 02125, USA.
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10
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Martini M, Pinto AX, Valverde O. Estrous cycle and sex affect cocaine-induced behavioural changes in CD1 mice. Psychopharmacology (Berl) 2014; 231:2647-59. [PMID: 24452696 DOI: 10.1007/s00213-014-3433-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 12/31/2013] [Indexed: 10/25/2022]
Abstract
RATIONALE Several findings on sex differences in cocaine response suggest a role for hormonal milieu in modulating the subjective effects of cocaine. Nitric oxide (NO) has been involved in the neurochemical, hormonal, and behavioral changes related to stress and anxiety. Within the brain, the anteroventral subdivision of the medial amygdala (MeAV) is an important area involved in processing emotional responses such as anxiety and a high density of NO-producing neurons is observed in this area. OBJECTIVES In this study, we hypothesize the possibility of sex/hormonal differences in response to cocaine and that these differences may reflect a change in the MeAV nitrergic system. We have examined cocaine's acute effects on nicotinamide adenine dinucleotide phosphate diaphorase (nadph-d) expression, as well as its effect on motor activity and anxiety in male and estrus and diestrus females. RESULTS Our results show that acute cocaine administration produces an increase in both anxiety behaviors and nadph-d expression in the MeAV. Male and diestrus female mice were more susceptible to these effects of cocaine than estrus female mice in which no differences were detected. In addition, we examined individual differences in male and female mice responding to intravenous cocaine reinforcement in a self-administration paradigm. Female mice acquired cocaine self-administration at a faster rate than males and showed a higher motivation to self-administer cocaine under a progressive ratio schedule of reinforcement. CONCLUSIONS Our data suggest a complex interaction between hormonal milieu and the behavioral and reinforcing effects of cocaine.
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Affiliation(s)
- Mariangela Martini
- Neurobiology of Behaviour Research Group (GReNeC), Department of Health and Experimental Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park C/Dr. Aiguader 88, 08003, Barcelona, Spain
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11
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Jones CG, Yang PB, Wilcox VT, Burau KD, Dafny N. Acute and chronic psychostimulant treatment modulates the diurnal rhythm activity pattern of WKY female adolescent rats. J Neural Transm (Vienna) 2014; 121:457-68. [PMID: 24482155 DOI: 10.1007/s00702-013-1141-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 12/12/2013] [Indexed: 11/28/2022]
Abstract
The psychostimulants considered the gold standard in the treatment of attention deficit hyperactivity disorder, one of the most common childhood disorders, are also finding their way into the hands of healthy young adults as brain augmentation to improve cognitive performance. The possible long-term effects of psychostimulant exposure in adolescence are considered controversial, and thus, the objective of this study was to investigate whether the chronic exposure to the psychostimulant amphetamine affects the behavioral diurnal rhythm activity patterns of female adolescent Wistar-Kyoto (WKY) rat. The hypothesis of this study is that change in diurnal rhythm activity pattern is an indicator for the long-term effect of the treatment. Twenty-four rats were divided into two groups, control (N = 12) and experimental (N = 12), and kept in a 12:12-h light/dark cycle in an open-field cage. After 5-7 days of acclimation, 11 days of consecutive non-stop behavioral recordings began. On experimental day 1 (ED1), all groups were given an injection of saline. On ED2 to ED7, the experimental group was injected with 0.6 mg/kg amphetamine followed by 3 days of washout from ED8 to ED10, and amphetamine re-challenge on ED11 similar to ED2. The locomotor movements were counted by the computerized animal activity monitoring system, and the cosinor statistical test analysis was used to fit a 24-h curve of the control recording to the activity pattern after treatment. The horizontal activity, total distance, number of stereotypy, vertical activity, and stereotypical movements were analyzed to find out whether the diurnal rhythm activity patterns were altered. Data obtained using these locomotor indices of diurnal rhythm activity pattern suggest that amphetamine treatment significantly modulates the locomotor diurnal rhythm activity pattern of female WKY adolescent rats.
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Affiliation(s)
- Cathleen G Jones
- Department of Neurobiology and Anatomy, The University of Texas-Medical School at Houston, P.O. Box 20708, Houston, TX, 77225, USA
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12
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Adult female rats' altered diurnal locomotor activity pattern following chronic methylphenidate treatment. J Neural Transm (Vienna) 2013; 120:1717-31. [PMID: 23893293 DOI: 10.1007/s00702-013-1063-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 06/25/2013] [Indexed: 12/25/2022]
Abstract
Methylphenidate (MPD) is one of the most prescribed pharmacological agents, which is also used for cognitive enhancement and recreational purposes. The objective of this study was to investigate the repetitive dose-response effects of MPD on circadian rhythm of locomotor activity pattern of female WKY rats. The hypothesis is that a change in the circadian activity pattern indicates a long-lasting effect of the drug. Four animal groups (saline control, 0.6, 2.5, and 10.0 mg/kg MPD dose groups) were housed in a sound-controlled room at 12:12 light/dark cycle. All received saline injections on experimental day 1 (ED 1). On EDs 2-7, the control group received saline injection; the other groups received 0.6, 2.5, or 10.0 mg/kg MPD, respectively. On ED 8-10, injections were withheld. On ED 11, each group received the same dose as EDs 2-7. Hourly histograms and cosine statistical analyses calculating the acrophase (ϕ), amplitude (A), and MESOR (M) were applied to assess the 24-h circadian activity pattern. The 0.6 and 2.5 mg/kg MPD groups exhibited significant (p < 0.05) change in their circadian activity pattern on ED 11. The 10.0 mg/kg MPD group exhibited tolerance on ED 11 and also a significant change in activity pattern on ED 8 compared to ED 1, consistent with withdrawal behavior (p < 0.007). In conclusion, chronic MPD administration alters circadian locomotor activity of adult female WKY rats and confirms that chronic MPD use elicits long-lasting effects.
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13
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Sex differences in novelty- and psychostimulant-induced behaviors of C57BL/6 mice. Psychopharmacology (Berl) 2013; 225:707-18. [PMID: 22975726 PMCID: PMC3547129 DOI: 10.1007/s00213-012-2860-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 08/20/2012] [Indexed: 01/16/2023]
Abstract
RATIONALE Women are more sensitive than men to psychostimulants and progress from initial use to drug addiction more quickly. The mouse has been an under-utilized model to study sex differences in psychostimulant action. Mice could serve as an ideal genetically tractable model for mechanistic studies into sex and hormone effects on psychostimulant behavior. OBJECTIVES The objective of this study was to characterize psychostimulant effects in male and female mice with a combination of automated data collection and behavioral observation. METHODS Male and female C57BL/6 mice (Charles River) were given a single dose or sequential ascending binge doses of D-amphetamine (AMPH) or cocaine (COC). Behavior was assessed in open field chambers using both automated photobeam interruptions and behavioral observations. Brain psychostimulant concentrations were determined at the time of maximum behavioral stimulation. RESULTS Psychostimulants induced behavioral activation in mice including both increased locomotion as detected with an automated system and a sequence of behaviors progressing from stereotyped sniffing at low doses to patterned locomotion and rearing at high doses. Females exhibited more patterned locomotion and a shift towards higher behavior scores after either psychostimulant despite having lower AMPH and equivalent COC brain levels as males. CONCLUSIONS Female C57BL/6 mice exhibit enhanced psychostimulant-induced behavior compared to males, similar to reports in rats. The combination of automated behavioral measures and behavioral observation was essential for verifying the existence of these differences. These results indicate the importance of testing both sexes when characterizing genetically manipulated mice to control for potential sex-specific effects.
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Baladi MG, Koek W, Aumann M, Velasco F, France CP. Eating high fat chow enhances the locomotor-stimulating effects of cocaine in adolescent and adult female rats. Psychopharmacology (Berl) 2012; 222:447-57. [PMID: 22418731 DOI: 10.1007/s00213-012-2663-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 02/06/2012] [Indexed: 12/24/2022]
Abstract
RATIONALE Dopamine systems vary through development in a manner that can impact drugs acting on those systems. Dietary factors can also impact the effects of drugs acting on dopamine systems. OBJECTIVES This study examined whether eating high fat chow alters locomotor effects of cocaine (1-56 mg/kg) in adolescent and adult female rats. METHODS Cocaine was studied in rats (n = 6/group) with free access to standard (5.7% fat) or high fat (34.3%) chow or restricted access to high fat chow (body weight matched to rats eating standard chow). RESULTS After 1 week of eating high fat chow (free or restricted access), sensitivity to cocaine was significantly increased in adolescent and adult rats, compared with rats eating standard chow. Sensitivity to cocaine was also increased in adolescent rats with restricted, but not free, access to high fat chow for 4 weeks. When adolescent and adult rats that previously ate high fat chow ate standard chow, sensitivity to cocaine returned to normal. In adolescent and adult female rats eating high fat chow, but not those eating standard chow, sensitivity to cocaine increased progressively over once weekly tests with cocaine (i.e., sensitization) in a manner that was not statistically different between adolescents and adults. CONCLUSIONS These results show that eating high fat chow alters sensitivity of female rats to acutely administered cocaine and also facilitates the development of sensitization to cocaine. That the type of food consumed can increase drug effects might have relevance to vulnerability to abuse cocaine in the female population.
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Affiliation(s)
- Michelle G Baladi
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA
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15
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Justo C, Carneiro-de-Oliveira P, DeLucia R, Aizenstein M, Planeta C. Repeated exposure of adolescent rats to oral methylphenidate does not induce behavioral sensitization or cross-sensitization to nicotine. Braz J Med Biol Res 2010; 43:651-6. [DOI: 10.1590/s0100-879x2010007500042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 04/07/2010] [Indexed: 05/26/2023] Open
Affiliation(s)
| | | | | | | | - C.S. Planeta
- Universidade Estadual Paulista, Brasil; Universidade Federal de São Carlos, Brasil
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16
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Segarra AC, Agosto-Rivera JL, Febo M, Lugo-Escobar N, Menéndez-Delmestre R, Puig-Ramos A, Torres-Diaz YM. Estradiol: a key biological substrate mediating the response to cocaine in female rats. Horm Behav 2010; 58:33-43. [PMID: 20026119 PMCID: PMC3621914 DOI: 10.1016/j.yhbeh.2009.12.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 12/03/2009] [Accepted: 12/04/2009] [Indexed: 12/19/2022]
Abstract
A consistent finding in drug abuse research is that males and females show differences in their response to drugs of abuse. In women, increased plasma estradiol is associated with increased vulnerability to the psychostimulant and reinforcing effects of drugs of abuse. Our laboratory has focused on the role of estradiol in modulating the response to cocaine. We have seen that ovariectomy increases the locomotor response to a single cocaine injection, whereas estradiol exacerbates the locomotor response to repeated cocaine administration. Cocaine-induced sensitization of brain activity, as measured by fMRI, is also dependent on plasma estradiol. Moreover, we observed that although all ovariectomized rats show conditioned place preference to cocaine, it is more robust in ovariectomized rats with estradiol. Opioid receptors are enriched in brain regions associated with pleasure and reward. We find that in females, the effectiveness of kappa opioid agonists in decreasing the locomotor response to repeated cocaine varies with plasma estradiol. We also find that estradiol regulates the density of mu opioid receptors in brains areas associated with reward. These data hint that in females, estradiol modulates the behavioral effects of cocaine by regulating mu and kappa opioid signaling in mesocorticolimbic brain structures. Identifying the mechanisms that mediate differences in vulnerability to drugs of abuse may lead to effective therapeutic strategies for the treatment and prevention of addiction and relapse. We encourage health practitioners treating persons addicted to drugs to consider gender differences in response to particular pharmacotherapies, as well the sex steroid milieu of the patient.
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Affiliation(s)
- Annabell C Segarra
- University of Puerto Rico, Department of Physiology, School of Medicine, PO Box 365067, San Juan, Puerto Rico 00936-5067.
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17
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Psychostimulants given in adolescence modulate their effects in adulthood using the open field and the wheel-running assays. Brain Res Bull 2010; 82:208-17. [PMID: 20362034 DOI: 10.1016/j.brainresbull.2010.03.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Revised: 03/23/2010] [Accepted: 03/24/2010] [Indexed: 02/06/2023]
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18
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Askenasy EP, Taber KH, Yang PB, Dafny N. METHYLPHENIDATE (RITALIN): BEHAVIORAL STUDIES IN THE RAT. Int J Neurosci 2009; 117:757-94. [PMID: 17454243 DOI: 10.1080/00207450600910176] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Attention Deficit Hyperactivity Disorder (ADHD) is a neuropsychiatric syndrome with an onset in childhood characterized by an inability to remain focused or to concentrate for prolonged periods of time. Children suffering from this disease are many times described as either inattentive or as hyperactive-impulsive depending on what form of the disease they manifest. Methylphenidate is the preferred treatment for this behavioral disorder and is used for long term disease management. Much still remains unknown concerning this stimulant and its effects on behavior and future abuse potential are pertinent questions. Since animal models are used to study the mechanism of drug action and rats are used often in drug studies, the objective of this review is to summarize the research reports that mainly have used rats as the model to investigate the action of methylphenidate. Topics discussed in this review include: (1) What effect does a single dose of methylphenidate have on locomotion activity; (2) Does repeated administration of methylphenidate result in tolerance or sensitization; and (3) Does methylphenidate have rewarding properties as measured by the self-administration and condition placed preference paradigms.
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Affiliation(s)
- Erik P Askenasy
- Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas 77225, USA
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19
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Zakharova E, Wade D, Izenwasser S. Sensitivity to cocaine conditioned reward depends on sex and age. Pharmacol Biochem Behav 2008; 92:131-4. [PMID: 19032962 DOI: 10.1016/j.pbb.2008.11.002] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 10/27/2008] [Accepted: 11/03/2008] [Indexed: 11/17/2022]
Abstract
Human and animal laboratory studies show that females and males respond differently to drugs and that drug administration during adolescence leads to different behavioral effects than during adulthood. Adult female rats are more sensitive to the behavioral effects of cocaine than adult males, but it is not known if the same effect of sex exists during adolescence. In the present study, sensitivity to the conditioned reward of cocaine was evaluated using a conditioned place preference (CPP) paradigm where adolescent (PND 34) and adult (PND 66) male and female rats were trained and tested for the development of CPP to multiple doses of cocaine. Female rats developed CPP at lower doses than males, regardless of age. In addition, adolescent male and female rats established a CPP at lower doses of cocaine than adult male and female rats, respectively. Thus, both age and sex altered cocaine conditioned reward with the order of sensitivity being adolescent females > adult females > adolescent males > adult males. These data show that adolescents are more sensitive to the conditioned rewarding properties of cocaine than adults and that females respond to lower doses of cocaine compared to males regardless of age.
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Affiliation(s)
- Elena Zakharova
- Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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20
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Caster JM, Walker QD, Kuhn CM. A single high dose of cocaine induces differential sensitization to specific behaviors across adolescence. Psychopharmacology (Berl) 2007; 193:247-60. [PMID: 17426961 DOI: 10.1007/s00213-007-0764-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Accepted: 03/06/2007] [Indexed: 11/28/2022]
Abstract
RATIONALE Adolescence is a critical period for drug addiction. Acute stimulant exposure elicits different behavioral responses in adolescent and adult rodents. The same biological differences that mediate age-specific behavioral responsiveness to stimulants in rodents could contribute to increased addiction vulnerability in adolescent humans. OBJECTIVES This study compared the ability of a single high dose of cocaine (40 mg/kg) to induce behavioral sensitization to a challenge dose of cocaine (10 mg/kg) 24 h later in young adolescent postnatal day 28 (PN 28), mid-adolescent (PN 42), and young adult (PN 65) male rats. Horizontal activity was resolved into ambulatory and non-ambulatory movements. An observational behavioral rating was obtained by recording specific behaviors. We examined if individual behavioral responses to novelty and cocaine correlate with sensitization in each age group. RESULTS Single dose cocaine pretreatment induced behavioral sensitization to non-ambulatory horizontal activity, sniffing behaviors, and stereotypies in animals of all ages. Ambulatory sensitization was observed only in the youngest adolescents. Cocaine pretreatment caused greater increases in stereotypies in the young adolescents than in adults. The magnitude of the behavioral response to the initial cocaine treatment was positively correlated with the magnitude of sensitization in individual young adolescents. High levels of novelty-induced ambulatory activity only correlated with the magnitude of ambulatory sensitization in the youngest adolescents. CONCLUSIONS We conclude that a single high dose of cocaine produces age-specific patterns of behavioral sensitization. Young adolescent rats appear to be more sensitive than adults to some of the behavioral alterations induced by a single high dose of cocaine.
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Affiliation(s)
- Joseph M Caster
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Room 100-B, Research Park Building 2, Box 3813, Durham, NC 27710, USA
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21
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Abstract
It is well known that most people who use psychoactive drugs started as teenagers. In spite of this, there has been little preclinical research on the effects of psychostimulants during adolescence. Recently, however, a number of laboratories have begun to focus on drug effects in adolescents as compared with adults. The data show that there are unique responses to drugs during this period of development. This review will focus on our current understanding of neurochemical and behavioral drug effects during adolescence.
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Affiliation(s)
- Sari Izenwasser
- Department of Psychiatry and Behavioral Sciences, University of Miami, School of Medicine, Miami, FL 33136, USA.
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22
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Allott K, Redman J. Are there sex differences associated with the effects of ecstasy/3,4-methylenedioxymethamphetamine (MDMA)? Neurosci Biobehav Rev 2007; 31:327-47. [PMID: 17109962 DOI: 10.1016/j.neubiorev.2006.09.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 09/28/2006] [Accepted: 09/28/2006] [Indexed: 11/25/2022]
Abstract
Sex has been identified as an important factor in moderating the effects of several drugs of abuse. Given the increasing popularity of ecstasy (3,4-methylenedioxymethamphetamine [MDMA]) use, it is important for researchers and clinicians to understand the factors that may influence its pharmacological actions to improve education, harm reduction and treatment efforts. This review focuses on preclinical and clinical research that examines the role of sex as an independent variable in the effects of ecstasy/MDMA. A systematic search of PsycINFO and MEDLINE electronic databases from 1966 to April 2006 was conducted. Both preclinical and clinical studies show a sexually dimorphic pattern in the acute, subacute and possibly long-term effects of ecstasy/MDMA. Specifically, adult females are more sensitive than males to the acute and subacute physical and psychological effects of ecstasy/MDMA and long-term alterations in aspects of 5-HT functioning. Conversely, males are more sensitive to the acute physiological effects of ecstasy/MDMA. These findings are consistent with research outcomes reported for other substances such as amphetamines and cocaine. Potential reasons for these sex differences and directions for future research are discussed.
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Affiliation(s)
- Kelly Allott
- Department of Psychology, Monash University, Vic. 3800, Australia.
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23
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Yang PB, Swann AC, Dafny N. Acute and chronic methylphenidate dose-response assessment on three adolescent male rat strains. Brain Res Bull 2006; 71:301-10. [PMID: 17113960 PMCID: PMC2048685 DOI: 10.1016/j.brainresbull.2006.09.019] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 09/18/2006] [Accepted: 09/20/2006] [Indexed: 02/04/2023]
Abstract
Methylphenidate (MPD), commonly known as Ritalin, is the most frequently prescribed drug to treat children and adults with attention deficit hyperactivity disorder (ADHD). Adolescence is a period of development involving numerous neuroplasticities throughout the central nervous system (CNS). Exposure to a psychostimulant such as MPD during this crucial period of neurodevelopment may cause transient or permanent changes in the CNS. Genetic variability may also influence these differences. Thus, the objective of the present study was to determine whether acute and chronic administration of MPD (0.6, 2.5, or 10.0mg/kg, i.p.) elicit effects among adolescent WKY, SHR, and SD rats and to compare whether there were strain differences. An automated, computerized, open-field activity monitoring system was used to study the dose-response characteristics of acute and repeated MPD administration throughout the 11-day experimental protocol. Results showed that all three adolescent rat groups exhibited dose-response characteristics following acute and chronic MPD administration, as well as strain differences. These strain differences depended on the MPD dose and locomotor index. Chronic treatment of MPD in these animals did not elicit behavioral sensitization, a phenomenon described in adult rats that is characterized by the progressive augmentation of the locomotor response to repeated administration of the drug. These results suggest that the animal's age at time of drug treatment and strain/genetic variability play a crucial role in the acute and chronic effect of MPD and in the development of behavioral sensitization.
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Affiliation(s)
- Pamela B. Yang
- Semel Institute for Neuroscience and Human Behavior David Geffen School of Medicine at UCLA 740 Westwood Blvd., Room A8-144 Los Angeles, CA 90024
| | - Alan C. Swann
- Department of Psychiatry and Behavioral Sciences, The University of Texas-Medical School at Houston P.O. Box 20708, Houston, Texas 77225
| | - Nachum Dafny
- Department of Neurobiology and Anatomy, The University of Texas-Medical School at Houston P.O. Box 20708, Houston, Texas 77225
- *Corresponding author: , 713-500-5616 (Office), 713-500-2515 (Fax)
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Walker QD, Ray R, Kuhn CM. Sex differences in neurochemical effects of dopaminergic drugs in rat striatum. Neuropsychopharmacology 2006; 31:1193-202. [PMID: 16237396 DOI: 10.1038/sj.npp.1300915] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Previous data indicate that dopamine neurotransmission is differently regulated in male and female rats. The purpose of the present study was to investigate the dopamine transporter and autoreceptor as potential loci responsible for this sex difference. Fast cyclic voltammetry at carbon-fiber microelectrodes was used to monitor changes in electrically evoked levels of extracellular dopamine in the striata of anesthetized male and female rats before and after administration of an uptake inhibitor, a dopamine D2 antagonist, or a D3/D2 agonist. Administration of 40 mg/kg cocaine ip increased electrically-evoked extracellular dopamine concentrations in both sexes, but to a significantly greater extent in female striatum at the higher stimulation frequencies. The typical antipsychotic, haloperidol, increased dopamine efflux in both sexes but the effect was twice as large in the female striatum. The D3/D2 agonist quinpirole induced an unexpected, transient increase in dopamine efflux following high-frequency stimulation only in females, and evoked dopamine was higher in females across this entire time course. More detailed analysis of cocaine effects revealed no fundamental sex differences in the interaction of cocaine with DAT in vivo or in synaptosomes. These results indicate that nigrostriatal dopamine neurotransmission in the female rat is more tightly regulated by autoreceptor and transporter mechanisms, perhaps related by greater autoreceptor control of DAT activity. Thus, baseline sex differences in striatal dopamine regulation induce different pharmacologic responses. These results contribute to understanding sex differences in stimulant-induced locomotor activity in rats and may have broader implications for neurologic disorders and their pharmacotherapies in humans.
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Affiliation(s)
- Q David Walker
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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25
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Balda MA, Anderson KL, Itzhak Y. Adolescent and adult responsiveness to the incentive value of cocaine reward in mice: role of neuronal nitric oxide synthase (nNOS) gene. Neuropharmacology 2006; 51:341-9. [PMID: 16698049 DOI: 10.1016/j.neuropharm.2006.03.026] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/14/2006] [Accepted: 03/23/2006] [Indexed: 11/24/2022]
Abstract
A major concern in adolescent psychostimulant abuse is the long-term consequence of this practice, because early drug exposure may cause long-term adaptations, which render the organism more susceptible to drug abuse later in life. The incentive value of drug and natural reward in rodents is commonly assessed by the conditioned place preference (CPP) paradigm, which involves Pavlovian learning. The aims of the present study were to investigate: a) the acquisition, expression, maintenance and reinstatement of cocaine CPP from periadolescence (PD24-45) through adulthood (PD70); b) potential sexual dimorphism in adolescence and adulthood in response to cocaine-induced CPP; and c) the role of the neuronal nitric oxide synthase (nNOS) gene in long-term neural plasticity underlying responsiveness to cocaine and cocaine-associated cues. Adolescent wild type (WT) mice acquired significant cocaine (20 mg/kg) CPP that was maintained from PD24 through PD43. Upon extinction, CPP was reinstated in adulthood (PD70) following a priming injection of cocaine (5 mg/kg). In contrast, cocaine CPP acquired between PD26 and PD31 in adolescent nNOS knockout (KO) mice, was neither maintained nor reinstated by cocaine. There was no sexual dimorphism in adolescent WT and KO mice. Genotype differences and sexual dimorphism were observed in adult mice. Cocaine CPP in adult WT males (PD89-94) was maintained for 4 weeks post training, and subsequently reinstated by cocaine priming; the magnitude of CPP in adult WT males was lower than in female counterparts. CPP in adult KO males (PD88-93) was neither maintained nor reinstated by cocaine priming; in contrast, CPP in adult KO females was not significantly different from adult WT females. Results suggest that the nNOS gene is essential during adolescence of both sexes for the development of long-term neural plasticity underlying responsiveness to the incentive value of cocaine reward. Sexual dimorphism in response to cocaine CPP emerges in adulthood; nNOS contribution to long-term plasticity is therefore sexually dimorphic and age-dependent in female but not in male subjects.
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Affiliation(s)
- Mara A Balda
- Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA
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26
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Dafny N, Yang PB. The role of age, genotype, sex, and route of acute and chronic administration of methylphenidate: A review of its locomotor effects. Brain Res Bull 2006; 68:393-405. [PMID: 16459193 DOI: 10.1016/j.brainresbull.2005.10.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 09/27/2005] [Accepted: 10/03/2005] [Indexed: 10/25/2022]
Abstract
Children with attention deficit hyperactivity disorder (ADHD) are treated for extended periods of time with the psychostimulant methylphenidate (MPD). The psychostimulants cocaine, amphetamine, and MPD exhibit similar structural configuration and pharmacological profile. The consequence of the long-term use of psychostimulants such as MPD as treatment for ADHD in the developing brain of children is unknown. Repeated treatment with psychostimulants has been shown to elicit adverse effects in behavior, such as dependence, paranoia, schizophrenia, and behavioral sensitization. Behavioral sensitization and cross-sensitization between two drugs are used as experimental markers to determine the potential of a drug to develop dependence/addiction. Although there are many reviews written about behavioral sensitization involving psychostimulants, scarcely any have focused specifically on MPD-elicited behavioral sensitization and cross-sensitization with other psychostimulants. Moreover, the response to MPD and the expression of ADHD vary among females and males and among different populations due to genetic variability. Since the interpretation and synthesis of the data reported are controversial, this review focuses on the adverse effects of MPD and the role of age, sex, and genetic composition on the acute and chronic effects of MPD, such as MPD-elicited behavioral sensitization and cross-sensitization with amphetamine in animal models. Animal models of drug-induced locomotor stimulation, particularly locomotor sensitization, can be used to understand the mechanisms underlying human drug-induced dependence.
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Affiliation(s)
- Nachum Dafny
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, P.O. Box 20708, Houston, TX 77225, USA.
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Harrod SB, Mactutus CF, Browning CE, Welch M, Booze RM. Home cage observations following acute and repeated IV cocaine in intact and gonadectomized rats. Neurotoxicol Teratol 2005; 27:891-6. [PMID: 16214304 DOI: 10.1016/j.ntt.2005.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 07/08/2005] [Accepted: 07/11/2005] [Indexed: 11/25/2022]
Abstract
The purpose of the present experiment was to examine the effects of acute and repeated intravenous (IV) cocaine on rat behavior in the home cage environment. An observational sampling method was used. Pair-housed, male, female, castrated (CAST), and ovariectomized (OVX) rats were administered daily IV cocaine injections (3.0 mg/kg/injection) in the home cage for 13 consecutive days, and observations occurred after the 1st and 13th injections. The incidence, i.e., occurrence or nonoccurrence of a behavior, was recorded according to a behavioral profile comprised of 11 behaviors. Data were analyzed as locomotor composite and orofacial composite scores. Behaviors not amenable for combination into a composite incidence score were evaluated independently (e.g., still behavior). Females exhibited more locomotor incidence scores than males following acute injection and more still behavior after repeated cocaine administration. Females exhibited more locomotor activity than OVX rats following acute, but not repeated, cocaine injection. There were no differences between the male and CAST rats on days 1 or 13. CAST rats exhibited more still behavior than OVX following only acute cocaine administration. This study indicates that IV cocaine-induced sex differences and the effects of gonadectomy can be measured in the home cage, and furthermore, describes a simple method to screen changes in cocaine-induced locomotor behaviors in the absence of automated equipment.
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Affiliation(s)
- Steven B Harrod
- Department of Psychology, University of South Carolina, Columbia, SC 29208, USA.
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Harrod SB, Booze RM, Welch M, Browning CE, Mactutus CF. Acute and repeated intravenous cocaine-induced locomotor activity is altered as a function of sex and gonadectomy. Pharmacol Biochem Behav 2005; 82:170-81. [PMID: 16139878 DOI: 10.1016/j.pbb.2005.08.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 08/02/2005] [Accepted: 08/10/2005] [Indexed: 11/29/2022]
Abstract
The present experiment examined the effects of sex and gonadectomy on cocaine-induced locomotor activity via intravenous (IV) cocaine. Male, female, castrated (CAST), and ovariectomized (OVX) rats received daily IV cocaine injections (3.0 mg/kg/injection) for 13 consecutive days. Locomotor activity was measured in automated activity chambers for 60 min following the baseline-saline administration and after the 1st and 13th cocaine injections. Observational time sampling was also performed, and the observational data were grouped into locomotor and orofacial composite incidence scores. Females exhibited more cocaine-induced locomotor activity, rearing, and locomotor incidence compared to males. The orofacial data revealed a sex difference in the expression of behavioral sensitization: females exhibited more orofacial behaviors than males after repeated, but not acute, cocaine injection. Females exhibited more cocaine-induced locomotor activity, rearing, and locomotor incidence compared to OVX rats, but exhibited less orofacial incidence following acute cocaine administration. There were no differences between male and CAST rats. CAST rats showed more locomotor incidence than OVX after repeated, but not acute, cocaine injection. CAST rats exhibited behavioral sensitization, whereas OVX rats' locomotor incidence did not change with repeated cocaine injection. CAST rats showed less orofacial incidence than OVX after acute, but not repeated, cocaine injection. These findings demonstrate sex differences in response to IV cocaine and replicate earlier findings which show that OVX attenuates increased locomotor activity in females. Furthermore, these findings suggest that IV cocaine administration produces behavioral differences between male and female rats in the absence of circulating gonadal hormones.
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Affiliation(s)
- Steven B Harrod
- Department of Psychology, University of South Carolina, 1512 Pendleton Street, Columbia, SC 29208, USA.
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Wansaw MP, Lin SN, Morrell JI. Plasma cocaine levels, metabolites, and locomotor activity after subcutaneous cocaine injection are stable across the postpartum period in rats. Pharmacol Biochem Behav 2005; 82:55-66. [PMID: 16115667 PMCID: PMC1850947 DOI: 10.1016/j.pbb.2005.07.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Revised: 07/05/2005] [Accepted: 07/15/2005] [Indexed: 11/19/2022]
Abstract
Plasma levels of cocaine (COC) and two of its principle metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME) were determined by liquid chromatography-tandem mass spectrometry (LC/MS/MS) in samples collected up to 3 h after a subcutaneous injection of cocaine (10 mg/kg) on six different days between days 4 and 24 postpartum, a period of dramatic change in the endocrine state of the female rat. Locomotor activity was measured in the same animals during this period using automated animal activity monitors. Additional measures in males provide a link to existing literature. We found that plasma levels of cocaine and its metabolites, as well as their respective time courses, are remarkably uniform across the postpartum period in female rats, as are the effects of cocaine on locomotor activity. Data from males show accord with prior published values. COC and BE, but not EME levels, were higher in males, and the time courses of COC and BE levels after injection varied somewhat between postpartum females and males; however, neither baseline nor cocaine-induced locomotor activity differed between postpartum females and males. We conclude that in the postpartum rat, there are no significant differences in the peripheral processing or general accessibility of cocaine to the brain to activate motor systems across the postpartum period. These data are critical to our understanding of differences in the reward salience of cocaine across the postpartum period and in other adult rat models [Mattson BJ, Williams S, Rosenblatt JS, Morrell JI. Comparison of two positive reinforcing stimuli: pups and cocaine throughout the postpartum period. Behav Neurosci 2001;115:683-94, Mattson BJ, Williams SE, Rosenblatt JS, Morrell JI. Preferences for cocaine- or pup-associated chambers differentiate otherwise behaviorally identical postpartum maternal rats. Psychopharmacology (Berl) 2003;167:1-8].
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Affiliation(s)
- Michael P Wansaw
- Preclinical Pharmacology Laboratory, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont, MA 02478, USA.
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Zhou W, Cunningham KA, Thomas ML. Estrogen effects on the hyperactivity induced by (+)-MDMA and cocaine in female rats. Behav Neurosci 2003; 117:84-94. [PMID: 12619911 DOI: 10.1037/0735-7044.117.1.84] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study compared the effects of estrogen (E) on the hyperactivity induced by (+)-3,4-methylenedioxymethamphetamine (MDMA) with E effects on cocaine-evoked hyperactivity in female rats. Sprague-Dawley rats were ovariectomized (OVX); half of them received a 17beta-estradiol (E2) implant (OVX + E). Three weeks later, rats received saline, (+)-MDMA (1, 2, or 4 mg/kg) or cocaine (5, 10, or 20 mg/kg), and locomotor activity was monitored. OVX + E rats exhibited greater locomotor hyperactivity in response to both psychostimulants than did OVX rats. The enhanced response to cocaine appeared within 5 min following drug injection whereas the enhanced response to (+)-MDMA was delayed for approximately 30 min. The differential effects of E on hyperactivity may be due to the unique profiles of DA and 5-HT in response to (+)-MDMA and cocaine.
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Affiliation(s)
- Wenxia Zhou
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77555-1031, USA
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Tirelli E, Laviola G, Adriani W. Ontogenesis of behavioral sensitization and conditioned place preference induced by psychostimulants in laboratory rodents. Neurosci Biobehav Rev 2003; 27:163-78. [PMID: 12732232 DOI: 10.1016/s0149-7634(03)00018-6] [Citation(s) in RCA: 265] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The present review deals mainly with the ontogenesis of two important phenomena involved in vulnerability to several neuropsychiatric disorders, namely with drug-induced sensitization (both contextual and non-contextual) and with conditioned place preference. The term 'infancy' covers the first three postnatal weeks during development in rats and mice. Conversely, the term 'adolescence' may cover the whole postnatal period ranging from weaning (PND 21) to adulthood (at least PND 60) or specifically the period around the onset of puberty (animals aged 33-44 days). Recent studies in rats demonstrated that the establishment of a context-dependent sensitization appears during the first (for repeated drug administration) or during the second (for a single drug administration) postnatal week. However, the memory of drug-context association is transient in developing pups (lasting one or two days following the drug pretreatment). The long-term retention of drug-context associations matures progressively, and is complete by the third week of postnatal life. Finally, those mechanisms responsible for an adult-like profile of context-independent pharmacological sensitization appear later during ontogenesis, being mature by the fourth week of postnatal life. Another set of experiments extended this ontogenetic characterization by comparing adolescent and adult mice. When compared to the latter, the former subjects exhibit a greater amphetamine-induced locomotor sensitization, almost no sensitization of aversive stereotyped behaviors, and a less marked place conditioning. The strength of the drug-induced place conditioning was also directly compared with the unconditioned novelty-seeking drive. In conclusion, neonatal rats are able to show a relatively short-lasting retention of sensitized drug effects (short-term sensitization), whereas the ability to exhibit relatively long-lasting sensitized effects matures progressively during infancy (long-term sensitization). On the other hand, adolescent mice show a reduced sensitization of drug-induced psychotic symptoms, together with a more marked sensitization of arousing and euphorigenic properties of the drug and a reduced incentive memory of its hedonic effects. These age-related changes do imply very different degrees of vulnerability to drug addiction and several other neuropsychiatric disorders.
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Affiliation(s)
- Ezio Tirelli
- Behavioral Neuroscience and Experimental Psychopharmacology Laboratory, Department of Cognitive Sciences, University of Liege, Boulevard du Rectorat B32, B-4000 Liege, Belgium.
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Walker QD, Nelson CJ, Smith D, Kuhn CM. Vaginal lavage attenuates cocaine-stimulated activity and establishes place preference in rats. Pharmacol Biochem Behav 2002; 73:743-52. [PMID: 12213518 DOI: 10.1016/s0091-3057(02)00883-3] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Sex and estrous cycle stage affect psychostimulant responses in animals. Cycle stage is typically monitored by vaginal lavage. The present studies tested the hypothesis that vaginal lavage modifies behavioral responses to acute cocaine. Female rats were restrained by briefly holding the tail for either vaginal lavage or touching the thigh, or were undisturbed, for 7-10 days prior to testing. Although habituation to the open-field test chamber was equal in each group, repeated lavage decreased horizontal activity relative to naive rats following acute cocaine (10 mg/kg ip). Lavage and touch attenuated cocaine-stimulated vertical activity. A single lavage prior to testing did not affect cocaine-stimulated motor behavior. Estrous cycle influenced motor activity only in nonlavaged rats. The high cocaine-induced responding observed in proestrous and estrous nonlavaged rats was completely blocked by vaginal lavage. A separate experiment tested the ability of vaginal lavage to establish a conditioned place preference. Vaginal lavage immediately prior to the conditioning session, but neither lavage after conditioning nor touch before, induced a significant preference. These results suggest that vaginal lavage serves as a reinforcing stimulus and interacts with a neural substrate that mediates enhanced locomotor responses to cocaine during proestrus and estrus.
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Affiliation(s)
- Q David Walker
- Department of Pharmacology, 401 Bryan Research Building, Box 3813, Duke University Medical Center, Durham, NC 27710, USA
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Tirelli E. Day-by-day maturation of the long-term expression of cocaine sensitization acquired before weaning in the rat. Behav Neurosci 2001; 115:1101-10. [PMID: 11584923 DOI: 10.1037/0735-7044.115.5.1101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study aimed to identify the ontogenetic period during which long-term expression of behavioral sensitization to cocaine begins to emerge. Rat pups aged 4, 8, 12, or 16 days received a pretreatment of 4 daily injections of 15 mg/kg sc cocaine paired with the test chamber for 45 min. Pups were then tested for sensitization in that context after abstinence intervals ranging from 2 to 10 days. On test days, pups were videotaped, and their behavior was scored later. Sensitization was detected after intervals of 2, 4, 5, or 9 days in pups aged 4-7, 8-11, 12-15, or 16-19 days during pretreatment, respectively. These results suggest that the mechanisms for long-term retention of sensitization mature incrementally in the rat, starting to emerge gradually after the 1st week of age, whereas those relevant to short-term retention and initiation of sensitization are present earlier.
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Affiliation(s)
- E Tirelli
- Université de Liège, Laboratoire de Psychopharmacologie Expérimentale, Belgium.
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Abstract
The current study investigated ovarian modulation of the locomotor response to cocaine in rats. Ovariectomy in females lowered the response to cocaine (10 mg/kg i.p.), whereas castration did not change that of males. The locomotor responses of prepubertal males and females to cocaine were similar. However, the postpubertal sex difference resulted from a fall in cocaine-stimulated locomotion in males rather than a rise in females. Neonatal testosterone treatment of female rat pups decreased the response to cocaine in adulthood. These findings suggest that both the activational and organizational effects of gonadal steroids contribute to the greater response of females to cocaine.
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Affiliation(s)
- C M Kuhn
- Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Abstract
Play behaviours are exhibited by many mammalian species. The similarity of such behaviour across children, non-human primates and rats makes it an especially appropriate target for the investigation of drug- or toxicant-induced disruption. In this study the acute effects of cocaine on play behaviour in male and female Sprague-Dawley rats was assessed. Same-sex dyads of rats (postnatal day 35-36) were separated 24 h prior to testing. On the following day, one or both rats of the dyad were injected with the same dose of cocaine (0, 2.5, 5.0 or 20.00 mg/kg). Thirty minutes later the rats were placed together and, after 5 min of habituation, the frequency of pins and crawl-overs were measured for each subject. In dyads in which both rats were treated, crawl-overs and pinning behaviour were decreased by 20 mg/kg cocaine. In dyads in which only one rat was treated, there was marginal effect of cocaine treatment on pinning frequency, while crawl-overs were unaffected. Pinning frequency was not sexually dimorphic in either type of dyad; however, crawl-overs were more frequently exhibited by females in dyads in which only one rat was treated. Thus, pinning behaviour in juvenile rats appears somewhat more sensitive to cocaine-induced disruption than crawl-over behaviours. Additionally, the presence of an untreated rat appears to attenuate the play-disrupting effects of cocaine on pinning frequency.
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Affiliation(s)
- S A Ferguson
- Division of Neurotoxicology, National Center for Toxicological Research/FDA, Jefferson, Arkansas 72079, USA.
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Walker QD, Rooney MB, Wightman RM, Kuhn CM. Dopamine release and uptake are greater in female than male rat striatum as measured by fast cyclic voltammetry. Neuroscience 2000; 95:1061-70. [PMID: 10682713 DOI: 10.1016/s0306-4522(99)00500-x] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The present studies investigated sexual dimorphisms in dopamine release and uptake using fast-scan cyclic voltammetry in anesthetized rats and in brain slices. Electrical stimulation of the medial forebrain bundle of anesthetized rats at high frequency (60 Hz) elicited significantly more extracellular dopamine in the caudate nucleus of females than males. This sex difference was apparent over a range of current intensities applied to the stimulating electrode. Local electrical stimulation of brain slices in vitro verified in vivo results as more extracellular dopamine was elicited by single and 10 pulse stimulations in the caudate nucleus of females. Kinetic analysis of in vivo and in vitro dopamine overflow data indicated that dopamine release (the concentration of dopamine released per stimulus pulse) and the maximal velocity of dopamine uptake are greater in female rats, but the affinity of the transporter for dopamine was the same in males and females. None of these three parameters varied across the female estrous cycle. Linear regression analysis of dopamine release versus maximal uptake velocity data indicated a significant association of release and uptake sites in each sex and regression lines for males and females virtually overlapped. One explanation for these results is greater dopamine neuron terminal density in female caudate nucleus. These sexual dimorphisms in dopaminergic neurotransmission provide a novel, plausible mechanism to explain robust sex differences in behavioral responses of rats to psychostimulant drugs and may have implications for human neurological disorders and drug abuse.
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Affiliation(s)
- Q D Walker
- Department of Pharmacology, Duke University Medical Center, Durham, NC 27710, USA
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Abstract
After repeated intermittent exposure to psychostimulants, an increase in the behavioral response to the drug is observed. The development of this sensitized response is greatly influenced by environmental cues. For example, when the pretreatments are administered in an environment distinct from the test, a sensitized response is often not observed. This finding has led some investigators to suggest that sensitization is completely context dependent. The present experiment established context-independent sensitization by administering pretreatments in an environment distinct from the test and measured the effects of pretreatment on potency and/or efficacy of subsequent cocaine administrations. Separate groups of rats received single or multiple daily injections of cocaine (10.0 mg/kg) or the saline vehicle in the home cage during a 5-day pretreatment phase. Ninety-six hours following the last of the pretreatment injections the locomotor-activating effects of cocaine (0.0, 5.0, 10.0, or 20.0 mg/kg) were measured. For control rats, a significant increase in motor activity was obtained following administration of the 20.0 mg/kg dose. Rats that received the cocaine pre-treatment became sensitized to cocaine's motor activating effects. For these rats, cocaine pretreatment produced a leftward shift in the dose-effect curve, consistent with an increased potency. The maximum locomotor response was not altered by pretreatment, suggesting that drug efficacy was not effected by preexposure. Thus, context-independent sensitization to cocaine reflects an increased potency, but not efficacy, of the drug.
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Affiliation(s)
- B Partridge
- Texas A & M University, Department of Psychology, College Station 77843, USA
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Tirelli E, Ferrara M. Neonatal and preweanling rats are able to express short-term behavioral sensitization to cocaine. Eur J Pharmacol 1997; 328:103-14. [PMID: 9218691 DOI: 10.1016/s0014-2999(97)83036-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The present study assessed the ability of suckling rats to express short-term behavioral sensitization to cocaine prior to weaning. Rat pups, aged either 3, 5, 10, 12, 17 or 19 days at the beginning of the experiment, were placed in a chamber after daily injection with cocaine (7.5 or 15 mg/kg. i.p.) for either 2 or 4 consecutive days, and were tested for behavioral responsiveness to cocaine in the same chamber 24 h later (at either 7, 14 or 21 days of age). Such a short post-treatment interval was adopted, along with a consistent pairing of the testing context with the drug effect and a sensitive technique of behavioral measurement (video recording), in order to maximize the possibility of detecting any cocaine sensitization. Locomotion was sensitized at all ages, after both regimens in 14-day-old pups, but solely after 2 injections in 21- and 4 injections in 7-day-old pups. Sensitization was also expressed via behaviors specific to each age. Four cocaine injections augmented cocaine-induced uncoordinated movements of head, paws and body (horizontal activity) in 7-day-old pups, and mouth movements in 14-day-old pups. In 21-day-old pups, sensitization was dose- and regimen-dependently expressed via adult-like stereotyped head movements. In neonatal 7-day-old pups, cocaine sensitization was also visible as reductions in immobility (both injection regimens). Contrary to previous studies, these results indicate that, given the use of an appropriate methodology, short-term sensitization to the motoric effects of cocaine can be expressed by suckling rats prior to weaning, even after relatively short regimens of daily injections.
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Affiliation(s)
- E Tirelli
- Biological Psychology and Pharmacopsychology Unit, University of Liège, Belgium.
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