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Liiver K, Imbeault S, Školnaja M, Kaart T, Kanarik M, Laugus K, De Wettinck J, Pulver A, Shimmo R, Harro J. Active vs passive novelty-related strategies: Sex differences in exploratory behaviour and monoaminergic systems. Behav Brain Res 2023; 441:114297. [PMID: 36641084 DOI: 10.1016/j.bbr.2023.114297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 01/02/2023] [Accepted: 01/10/2023] [Indexed: 01/13/2023]
Abstract
Sex differences are apparent in numerous behavioural characteristics. In order to compare and characterise male and female variability of exploratory behaviour, 365 male and 401 female rats were assessed in a task where a bimodal response distribution had previously been established in males. Female rats had significantly higher exploratory activity, and presented normal distribution of the behaviour, very differently from the bimodal distribution of males. No major effect of litter or oestrous cycle was detected. Several differences between male and female rats were found in monoamine metabolism measured ex vivo. Male rats had lower levels of dopamine (DA) in frontal cortex, and higher levels of 3,4-dihydroxyphenylacetic acid (DOPAC) in raphe area; higher levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in dorsal striatum but lower levels of 5-HT and 5-HIAA in locus coeruleus area, 5-HIAA levels were also lower in hippocampus as compared to females. Males had higher noradrenaline (NA) levels in hippocampus and lower normetanephrine (NMN) levels in striatum, in both brain regions male animals had lower NMN/NA ratio. No sex difference was found in accumbens. The only brain region with an interaction between sex and the expression of exploratory activity was raphe: Here 5-HT levels were lower, and DOPAC levels and DOPAC/DA and 5-HIAA/5-HT ratios higher in low exploring male but not female rats. Conclusively, female rats not only display higher levels of exploration but the population distribution of this behaviour is distinct; this may be related to differences in the monoaminergic systems between female and male animals.
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Affiliation(s)
- Kristi Liiver
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia
| | - Sophie Imbeault
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia
| | - Marianna Školnaja
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia; Laboratory Animal Centre, Tallinn University of Technology, Akadeemia Road 15, 12618 Tallinn, Estonia
| | - Tanel Kaart
- Institute of Veterinary Medicine and Animal Science, Estonian University of Life Sciences, 51006 Tartu, Estonia
| | - Margus Kanarik
- Division of Neuropsychopharmacology, Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu, Estonia
| | - Karita Laugus
- Division of Neuropsychopharmacology, Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu, Estonia
| | - Jade De Wettinck
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia
| | - Aleksander Pulver
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia
| | - Ruth Shimmo
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia
| | - Jaanus Harro
- School of Natural Sciences and Health, Tallinn University, Narva Road 25, 10120 Tallinn, Estonia; Division of Neuropsychopharmacology, Institute of Chemistry, University of Tartu, Ravila 14A, 50411 Tartu, Estonia; Institute of Biotechnology, HiLIFE, University of Helsinki, Viikinkaari 5D, 00014 Helsinki, Finland.
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Pisani F, Pisani V, Arcangeli F, Harding A, Singhrao SK. Locus Coeruleus Dysfunction and Trigeminal Mesencephalic Nucleus Degeneration: A Cue for Periodontal Infection Mediated Damage in Alzheimer's Disease? INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:1007. [PMID: 36673763 PMCID: PMC9858796 DOI: 10.3390/ijerph20021007] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/30/2022] [Accepted: 01/01/2023] [Indexed: 06/12/2023]
Abstract
Alzheimer's disease (AD) is a leading neurodegenerative disease with deteriorating cognition as its main clinical sign. In addition to the clinical history, it is characterized by the presence of two neuropathological hallmark lesions; amyloid-beta (Aβ) and neurofibrillary tangles (NFTs), identified in the brain at post-mortem in specific anatomical areas. Recently, it was discovered that NFTs occur initially in the subcortical nuclei, such as the locus coeruleus in the pons, and are said to spread from there to the cerebral cortices and the hippocampus. This contrasts with the prior acceptance of their neuropathology in the enthorinal cortex and the hippocampus. The Braak staging system places the accumulation of phosphorylated tau (p-tau) binding to NFTs in the locus coeruleus and other subcortical nuclei to precede stages I-IV. The locus coeruleus plays diverse psychological and physiological roles within the human body including rapid eye movement sleep disorder, schizophrenia, anxiety, and depression, regulation of sleep-wake cycles, attention, memory, mood, and behavior, which correlates with AD clinical behavior. In addition, the locus coeruleus regulates cardiovascular, respiratory, and gastrointestinal activities, which have only recently been associated with AD by modern day research enabling the wider understanding of AD development via comorbidities and microbial dysbiosis. The focus of this narrative review is to explore the modes of neurodegeneration taking place in the locus coeruleus during the natural aging process of the trigeminal nerve connections from the teeth and microbial dysbiosis, and to postulate a pathogenetic mechanism due to periodontal damage and/or infection focused on Treponema denticola.
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Affiliation(s)
- Flavio Pisani
- Programme Lead, MSc/MClinDent in Clinical Periodontology, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
| | - Valerio Pisani
- I.R.C.C.S. “Santa Lucia” Foundation, Neurology and Neurorehabilitation Unit, Via Ardeatina, 306, 00179 Rome, Italy
| | - Francesca Arcangeli
- Azienda Sanitaria Locale ASLRM1, Nuovo Regina Margherita Hospital, Geriatric Department-Advanced Centre for Dementia and Cognitive Disorders, Via Emilio Morosini, 30, 00153 Rome, Italy
| | - Alice Harding
- Dementia and Neurodegenerative Disease Research Group, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
| | - Sim K. Singhrao
- Dementia and Neurodegenerative Disease Research Group, Faculty of Clinical and Biomedical Sciences, School of Dentistry, University of Central Lancashire, Preston PR1 2HE, UK
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Améndola L, Weary D, Zobel G. Effects of personality on assessments of anxiety and cognition. Neurosci Biobehav Rev 2022; 141:104827. [PMID: 35970418 DOI: 10.1016/j.neubiorev.2022.104827] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/10/2022] [Accepted: 08/10/2022] [Indexed: 11/17/2022]
Abstract
Individual variation in responses to commonly used tests of anxiety and spatial memory is often reported. While this variation is frequently considered to be 'noise', evidence suggests that it is, at least partially, related to consistent individual differences in behavioral responses (i.e., personality). The same tests used to assess anxiety are often used to profile personality traits, but personality differences are rarely considered when testing treatment differences in anxiety. Focusing on the rat literature, we describe fundamental principles involved in anxiety and spatial memory tests and we discuss how personality differences and housing conditions can influence behavioral responses in these tests. We propose that an opportunity exists to increase stress resiliency in environmentally sensitive individuals by providing environmental enrichment. We conclude by discussing different approaches to incorporating personality measures into the design and analysis of future studies; given the potential that variation masks research outcomes, we suggest that a strategy which considers the individual and its housing can contribute to improving research reproducibility.
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Affiliation(s)
- Lucia Améndola
- Animal Welfare Program, University of British Columbia, Canada.
| | - Daniel Weary
- Animal Welfare Program, University of British Columbia, Canada.
| | - Gosia Zobel
- Animal Behaviour and Welfare Team, AgResearch Ltd., Ruakura Research Centre, 10 Bisley Road, Private Bag 3123, Hamilton 3214, New Zealand.
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Effect of Neuropeptide S Administration on Ultrasonic Vocalizations and Behaviour in Rats with Low vs. High Exploratory Activity. Pharmaceuticals (Basel) 2021; 14:ph14060524. [PMID: 34070724 PMCID: PMC8229755 DOI: 10.3390/ph14060524] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/26/2021] [Accepted: 05/27/2021] [Indexed: 12/20/2022] Open
Abstract
Neuropeptide S (NPS) is a peptide neurotransmitter that in animal studies promotes wakefulness and arousal with simultaneous anxiety reduction, in some inconsistency with results in humans. We examined the effect of NPS on rat ultrasonic vocalizations (USV) as an index of affective state and on behaviour in novel environments in rats with persistent inter-individual differences in exploratory activity. Adult male Wistar rats were categorised as of high (HE) or low (LE) exploratory activity and NPS was administered intracerebroventricularly (i.c.v.) at a dose of 1.0 nmol/5 µL, after which USVs were recorded in the home-cage and a novel standard housing cage, and behaviour evaluated in exploration/anxiety tests. NPS induced a massive production of long and short 22 kHz USVs in the home cage that continued later in the novel environment; no effect on 50 kHz USVs were found. In LE-rats, the long 22 kHz calls were emitted at lower frequencies and were louder. The effects of NPS on behaviour appeared novelty- and test-dependent. NPS had an anxiolytic-like effect in LE-rats only in the elevated zero-maze, whereas in HE-rats, locomotor activity in the zero-maze and in a novel standard cage was increased. Thus NPS appears as a psychostimulant peptide but with a complex effect on dimensions of affect.
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Kõiv K, Vares M, Kroon C, Metelitsa M, Tiitsaar K, Laugus K, Jaako K, Harro J. Effect of chronic variable stress on sensitization to amphetamine in high and low sucrose-consuming rats. J Psychopharmacol 2019; 33:1512-1523. [PMID: 31208275 DOI: 10.1177/0269881119856000] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Individual vulnerability to stress manifests in the interaction of innate properties and environment. There is a growing interest in the individual variability in vulnerability to stress and how it contributes to the development of psychiatric disorders. Intake of palatable substances is often measured in animal models. We have previously demonstrated that the consumption of sucrose solution is a stable trait in rats. AIMS The present study aimed to compare the sensitivity of rats with high vs low liquid sucrose consumption to chronic variable stress and the stress effect on behavioural sensitization to amphetamine. METHODS Male Wistar rats were subjected to a chronic stress regimen and subsequent repeated treatment with amphetamine (1 mg/kg, intraperitoneally). Fifty-kHz ultrasonic vocalizations, locomotor activity and stereotypies were measured. RESULTS In no-stress baseline conditions, the behavioural response to acute amphetamine was similar in rats with high vs low sucrose consumption. Prior chronic stress potentiated the effect of amphetamine only in rats with high sucrose consumption. Behavioural sensitization to repeated administration of amphetamine was observed in non-stressed rats with lower sucrose preference, but not in the respective stressed group that had increased monoamine turnover in the nucleus accumbens. In contrast, in rats with high sucrose preference the amphetamine sensitization effect was prevalent in stressed rats, but not in non-stressed animals. INTERPRETATION Chronic stress can change the psychostimulant effect but this depends on the inherent reward sensitivity of the animal. Trait-wise, sucrose intake reflects vulnerability to chronic stress and may interact with the development of addiction.
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Affiliation(s)
- Kadri Kõiv
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Marten Vares
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Cristina Kroon
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Mait Metelitsa
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Kai Tiitsaar
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Karita Laugus
- Department of Psychology, University of Tartu, Tartu, Estonia
| | - Külli Jaako
- Department of Pharmacology, University of Tartu, Tartu, Estonia
| | - Jaanus Harro
- Department of Psychology, University of Tartu, Tartu, Estonia
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Chronic stress sensitizes amphetamine-elicited 50-kHz calls in the rat: Dependence on positive affective phenotype and effects of long-term fluoxetine pretreatment. Pharmacol Biochem Behav 2018; 171:10-19. [DOI: 10.1016/j.pbb.2018.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 05/23/2018] [Indexed: 11/17/2022]
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Effect of Noradrenergic Neurotoxin DSP-4 and Maprotiline on Heart Rate Spectral Components in Stressed and Resting Rats. Bull Exp Biol Med 2017; 163:302-306. [PMID: 28744642 DOI: 10.1007/s10517-017-3790-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Indexed: 10/19/2022]
Abstract
The effects of intraperitoneal DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine, a noradrenergic neurotoxin) and maprotiline (an inhibitor of norepinephrine reuptake in synapses) on spectral components of heart rhythm variability were examined in outbred male and female rats treated with these agents in daily doses of 10 mg/kg for 3 days. At rest, DSP-4 elevated LF and VLF spectral components in male and female rats. Maprotiline elevated LF and VLF components in males at rest, increased HR and reduced all spectral components in resting females. Stress against the background of DSP-4 treatment sharply increased heart rate and reduced the powers of all spectral components (especially LF and VLF components). In maprotiline-treated rats, stress increased the powers of LF and VLF components. Thus, the central noradrenergic system participates in the formation of LF and VLF spectral components of heart rate variability at rest and especially during stressful stimulation, which can determine the phasic character of changes in the heart rate variability observed in stressed organism.
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O’Leary A, Kõiv K, Raudkivi K, Harro J. Antidepressants differentially affect striatal amphetamine-stimulated dopamine and serotonin release in rats with high and low novelty-oriented behaviour. Pharmacol Res 2016; 113:739-746. [DOI: 10.1016/j.phrs.2016.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Revised: 02/01/2016] [Accepted: 02/01/2016] [Indexed: 11/24/2022]
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Kõiv K, Metelitsa M, Vares M, Tiitsaar K, Raudkivi K, Jaako K, Vulla K, Shimmo R, Harro J. Chronic variable stress prevents amphetamine-elicited 50-kHz calls in rats with low positive affectivity. Eur Neuropsychopharmacol 2016; 26:631-43. [PMID: 26951611 DOI: 10.1016/j.euroneuro.2016.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 01/21/2016] [Accepted: 02/20/2016] [Indexed: 10/22/2022]
Abstract
The relationship between stress response and positive affective states is thought to be bidirectional: whilst stress can lead to a blunted hedonic response, positive affect reduces the negative effects of stress. We have previously shown that persistently high positive affectivity as measured by 50-kHz ultrasonic vocalizations (USVs) is protective against chronic variable stress (CVS). The present study examined the effect of CVS on 50-kHz USVs elicited by amphetamine administration, simultaneously considering the stable inter-individual differences in positive affectivity. Forty juvenile male Wistar rats were categorised as of high (HC) or low (LC) positive affectivity based on their 50-kHz USV response to imitation of rough-and-tumble play ('tickling'). As adults, the rats were subjected to four weeks of CVS, after which D-amphetamine was administered in five daily doses followed by a challenge dose (all 1mg/kg IP) nine days later. CVS reduced sucrose preference in LC-rats only. After CVS, amphetamine-elicited 50-kHz USVs were significantly reduced in LC-rats, the effect of stress in HC-rats being smaller and less consistent. In previously stressed and amphetamine-treated LC-rats, locomotor response to amphetamine was attenuated. In stressed LC-rats, DOPAC levels and dopamine turnover were increased in striatum after amphetamine treatment, and dopamine D1 receptor levels were upregulated in nucleus accumbens. LC-rats had lower isoleucine levels in frontal cortex. These results show that stress-related changes in response to amphetamine are dependent on inter-individual differences in positive affectivity both at neurochemical and behavioural levels, and further support the notion of higher vulnerability of animals with low positive affect.
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Affiliation(s)
- Kadri Kõiv
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia
| | - Mait Metelitsa
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia
| | - Marten Vares
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia
| | - Kai Tiitsaar
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia
| | - Karita Raudkivi
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia
| | - Külli Jaako
- Department of Pharmacology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 19, 50411 Tartu, Estonia
| | - Kaspar Vulla
- Department of Natural Sciences, School of Natural Sciences and Health, Tallinn University, Narva 29, 10120 Tallinn, Estonia
| | - Ruth Shimmo
- Department of Natural Sciences, School of Natural Sciences and Health, Tallinn University, Narva 29, 10120 Tallinn, Estonia
| | - Jaanus Harro
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
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Ross SB, Stenfors C. DSP4, a Selective Neurotoxin for the Locus Coeruleus Noradrenergic System. A Review of Its Mode of Action. Neurotox Res 2014; 27:15-30. [DOI: 10.1007/s12640-014-9482-z] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 06/05/2014] [Accepted: 06/07/2014] [Indexed: 12/19/2022]
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Matrov D, Vonk A, Herm L, Rinken A, Harro J. Activating effects of chronic variable stress in rats with different exploratory activity: association with dopamine d(1) receptor function in nucleus accumbens. Neuropsychobiology 2011; 64:110-22. [PMID: 21701229 DOI: 10.1159/000325224] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 01/23/2011] [Indexed: 01/11/2023]
Abstract
BACKGROUND/AIMS Rats display persistent behavioural phenotypes of low (LE) versus high (HE) exploratory activity in the exploration box paradigm. LE rats that prefer passive coping strategies show differential dopaminergic activity in the striatum. The main hypothesis of this study was that chronic variable stress (CVS) would have a higher impact on LE rats. METHODS Animals were submitted to a CVS regimen lasting 32 days that was followed by a behavioural test battery. The functional states of their dopamine D(1) and D(2) receptors were measured in the striatum and nucleus accumbens (NAcc). Cerebral oxidative metabolism was assessed via cytochrome c oxidase histochemistry in 65 brain regions. RESULTS CVS decreased weight gain, to a higher extent in LE rats, and lowered the sucrose preference after the first week, but habituation to the anhedonic effect had developed by the end of the experiment. CVS did not change the behavioural phenotypes initially assigned. No effect of stress on D(2) receptor function was found. Chronically stressed animals exhibited higher levels of social interaction and D(1) receptor-mediated cAMP accumulation in the NAcc, but not in the striatum. CVS was associated with higher oxidative metabolism levels in the anteroventral thalamus, median raphe nuclei and central periaqueductal grey matter. These changes after stress did not depend upon the exploratory phenotype. CONCLUSION This study revealed changes in brain biochemistry after habituation to CVS that might be implicated in successful adaptation to chronic stress.
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Affiliation(s)
- Denis Matrov
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tartu, Estonia
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Kõiv K, Zobel R, Raudkivi K, Kivastik T, Harro J. The effect of denervation of the locus coeruleus projections with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) on cocaine-induced locomotion and place preference in rats. Behav Brain Res 2011; 216:172-9. [DOI: 10.1016/j.bbr.2010.07.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 07/17/2010] [Accepted: 07/25/2010] [Indexed: 10/19/2022]
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Alttoa A, Kõiv K, Hinsley TA, Brass A, Harro J. Differential gene expression in a rat model of depression based on persistent differences in exploratory activity. Eur Neuropsychopharmacol 2010; 20:288-300. [PMID: 19854624 DOI: 10.1016/j.euroneuro.2009.09.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Revised: 09/18/2009] [Accepted: 09/28/2009] [Indexed: 12/26/2022]
Abstract
Affective disorders are often accompanied by changes in motivation and anxiety. We investigated the genome-wide gene expression patterns in an animal model of depression that separates Wistar rats belonging into clusters of persistently high anxiety/low motivation to explore and low anxiety/high motivation to explore (low explorers and high explorers, LE and HE, respectively), in three brain regions previously implicated in mood disorders (raphe, hippocampus and the frontal cortex). Several serotonin-, GABA-, and glutamatergic genes were differentially expressed in LE- and HE-rats. The analysis of Gene Ontology biological process terms associated with the differentially regulated genes identified a significant overrepresentation of genes involved in the neuron development, morphogenesis, and differentiation; the most enriched pathways from the Kyoto Encyclopedia of Genes and Genomes were the Wnt signalling, MAPK signalling, long-term potentiation, and long-term depression pathways. These findings corroborate some expression data from other models of depression, and suggest additional targets.
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Affiliation(s)
- Aet Alttoa
- Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Estonia
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Harro J. Inter-individual differences in neurobiology as vulnerability factors for affective disorders: implications for psychopharmacology. Pharmacol Ther 2009; 125:402-22. [PMID: 20005252 DOI: 10.1016/j.pharmthera.2009.11.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 11/25/2009] [Indexed: 10/20/2022]
Abstract
Susceptibility to affective disorders is individually different, and determined both by genetic variance and life events that cause significant differences in the CNS structure and function between individual subjects. Therefore it is plausible that search for the inter-individual differences in endophenotypes that mediate the effects of causal factors, both genetic and environmental, will reveal the substrates for vulnerability, help to clarify pathogenetic mechanisms, and possibly aid in developing strategies to discover better, more personalized treatments. This review first examines comparatively a number of animal models of human affect and affect-related disorders that rely on persistent inter-individual differences, and then highlights some of the neurobiological findings in these models that are compatible with much of research in human behavioural and personality traits. Many behaviours occur in specific combinations in several models, but often remarkable dissociations are observed, providing a variety of constellations of traits. It is concluded that more systematic comparative experimentation on behaviour and neurobiology in different models is warranted to reveal possible "building blocks" of affect-related personality common in animals and humans. Looking into the perspectives in psychopharmacology the focus is placed on probable associations of inter-individual differences with brain structure and function, personality and coping strategies, and psychiatric vulnerability, highlighting some unexpected interactions between vulnerability endophenotypes, adverse life events, and behavioural traits. It is argued that further studies on inter-individual differences in affect and underlying neurobiology should include formal modeling of their epistatic, hierarchical and dynamic nature.
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Affiliation(s)
- Jaanus Harro
- Department of Psychology, University of Tartu, Estonian Centre of Behavioural and Health Sciences, Tiigi 78, 50410 Tartu, Estonia.
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Nowak P, Nitka D, Kwieciński A, Jośko J, Drab J, Pojda-Wilczek D, Kasperski J, Kostrzewa RM, Brus R. Neonatal co-lesion by DSP-4 and 5,7-DHT produces adulthood behavioral sensitization to dopamine D(2) receptor agonists. Pharmacol Rep 2009; 61:311-8. [PMID: 19443944 DOI: 10.1016/s1734-1140(09)70037-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 02/18/2009] [Indexed: 11/29/2022]
Abstract
To assess the possible modulatory effects of noradrenergic and serotoninergic neurons on dopaminergic neuronal activity, the noradrenergic and serotoninergic neurotoxins DSP-4 N-(2-chlorethyl)-N-ethyl-2-bromobenzylamine (50.0 mg/kg, sc) and 5,7-dihydroxytryptamine (5,7-DHT) (37.5 microg icv, half in each lateral ventricle), respectively, were administered toWistar rats on the first and third days of postnatal ontogeny, and dopamine (DA) agonist-induced behaviors were assessed in adulthood. At eight weeks, using an HPLC/ED technique, DSP-4 treatment was associated with a reduction in NE content of the corpus striatum (> 60%), hippocampus (95%), and frontal cortex (> 85%), while 5,7-DHT was associated with an 80-90% serotonin reduction in the same brain regions. DA content was unaltered in the striatum and the cortex. In the group lesioned with both DSP-4 and 5,7-DHT, quinpirole-induced (DA D(2) agonist) yawning, 7-hydroxy-DPAT-induced (DA D(3) agonist) yawning, and apomorphine-induced (non-selective DA agonist) stereotypies were enhanced. However, SKF 38393-induced (DA D(1) agonist) oral activity was reduced in the DSP-4 + 5,7-DHT group. These findings demonstrate that DA D(2)- and D(3)-agonist-induced behaviors are enhanced while DA D(1)-agonist-induced behaviors are suppressed in adult rats in which brain noradrenergic and serotoninergic innervation of the brain has largely been destroyed. This study indicates that noradrenergic and serotoninergic neurons have a great impact on the development of DA receptor reactivity (sensitivity).
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Affiliation(s)
- Przemysław Nowak
- Department of Pharmacology, Medical University of Silesia, Zabrze, Poland.
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Alttoa A, Seeman P, Kõiv K, Eller M, Harro J. Rats with persistently high exploratory activity have both higher extracellular dopamine levels and higher proportion of D(2) (High) receptors in the striatum. Synapse 2009; 63:443-6. [PMID: 19184998 DOI: 10.1002/syn.20620] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Increases in both striatal dopamine release and the proportion of the D(2) receptors in the high affinity state (D(2) (High)) accompany the behavioral sensitization to psychostimulants, but it is not known whether the physiological substrate of the interindividual differences locomotor and exploratory behavior is similar. Thus, we examined whether persistently high spontaneous exploratory activity is associated with extracellular dopamine as well as the proportion of D(2) (High) in the striatum. Extracellular dopamine levels were found to be significantly higher in rats with high exploratory activity (high explorers, HE) as compared with low explorers (LE) in baseline conditions as well as after administration of amphetamine (0.5 mg/kg, i.p.). Also, the HE animals had significantly higher proportion of striatal D(2) (High) receptors than the LE-rats (43.8 +/- 4.4% and 22.5 +/- 1.5%, respectively). Thus, the present findings support the notion that concomitant higher extracellular dopamine levels and the proportion of D(2) (High) receptors in the striatum, whether naturally occurring and persistent or pharmacologically induced, are causally related to high behavioral activity.
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Affiliation(s)
- Aet Alttoa
- Department of Psychology, Centre of Behavioral and Health Sciences, University of Tartu, 50410 Tartu, Estonia
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17
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Vonk A, Reinart R, Rinken A. Modulation of adenylyl cyclase activity in rat striatal homogenate by dopaminergic receptors. J Pharmacol Sci 2008; 108:63-70. [PMID: 18818481 DOI: 10.1254/jphs.08019fp] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We have characterized the modulation of adenylyl cyclase (AC) activity by ligands of dopaminergic receptors in rat striatal homogenate and compared the results with receptor-ligand binding affinities. Despite the fact that rat striatum contains high level of both dopamine D(1) and D(2) receptors, only the D(1)-specific AC activation by agonists could be determined. All D(1)-receptor agonists (dopamine, dihydrexidine, and A 77636) used were able to increase cAMP accumulation in a concentration-dependent manner, while D(1)-receptor antagonists (SCH23390, SKF83566, and butaclamol) blocked the effects induced by the aforementioned agonists. At the same time, the D(2)-receptor agonist quinpirole and antagonist sulpiride had no effect on cAMP accumulation in striatal homogenate neither on the basal level nor on the activated level of AC, while inhibited [(3)H]raclopride binding to these membranes. Comparing the ligands of the D(1) receptor in modulating the activity of AC and displacing D(1)-receptor-specific radioligand [(3)H]SCH23390 binding revealed that the ligands modulate both of these processes with similar affinities. It indicates that under given experimental conditions, only dopamine D(1)-receptor-mediated stimulation of AC activity can be measured in membrane homogenate of rat striatum, while dopamine D(2)-receptor effects remain fully hidden.
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Affiliation(s)
- Argo Vonk
- Institute of Chemistry, University of Tartu, Jakobi 2, Tartu, Estonia
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18
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Viggiano D. The hyperactive syndrome: metanalysis of genetic alterations, pharmacological treatments and brain lesions which increase locomotor activity. Behav Brain Res 2008; 194:1-14. [PMID: 18656502 DOI: 10.1016/j.bbr.2008.06.033] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Revised: 06/26/2008] [Accepted: 06/29/2008] [Indexed: 01/01/2023]
Abstract
The large number of transgenic mice realized thus far with different purposes allows addressing new questions, such as which animals, over the entire set of transgenic animals, show a specific behavioural abnormality. In the present study, we have used a metanalytical approach to organize a database of genetic modifications, brain lesions and pharmacological interventions that increase locomotor activity in animal models. To further understand the resulting data set, we have organized a second database of the alterations (genetic, pharmacological or brain lesions) that reduce locomotor activity. Using this approach, we estimated that 1.56% of the genes in the genome yield to hyperactivity and 0.75% of genes produce hypoactivity when altered. These genes have been classified into genes for neurotransmitter systems, hormonal, metabolic systems, ion channels, structural proteins, transcription factors, second messengers and growth factors. Finally, two additional classes included animals with neurodegeneration and inner ear abnormalities. The analysis of the database revealed several unexpected findings. First, the genes that, when mutated, induce hyperactive behaviour do not pertain to a single neurotransmitter system. In fact, alterations in most neurotransmitter systems can give rise to a hyperactive phenotype. In contrast, fewer changes can decrease locomotor activity. Specifically, genetic and pharmacological alterations that enhance the dopamine, orexin, histamine, cannabinoids systems or that antagonize the cholinergic system induce an increase in locomotor activity. Similarly, imbalances in the two main neurotransmitters of the nervous system, GABA and glutamate usually result in hyperactive behaviour. It is remarkable that no genetic alterations pertaining to the GABA system have been reported to reduce locomotor behaviour. Other neurotransmitters, such as norepinephrine and serotonin, have a more complex influence. For instance, a decrease in norepinephrine synthesis usually results in hypoactive behaviour. However, a chronic increase in norepinephrine may result in hypoactivity too. Similarly, changes in both directions of serotonin levels may reduce locomotor activity, whereas alterations in specific serotonin receptors can induce hyperactivity. The lesion of at least 12 different brain regions can increase locomotor activity too. Comparatively, few focal lesions decrease locomotor activity. Finally, a large number of toxic events can increase locomotor activity, particularly if delivered during the prepuberal time window. These data show that there is a net imbalance in the number of altered genes/brain lesions/toxics that induce hyperactivity versus hypoactive behaviour. Although some of these data may be explained in terms of the activating role of subcortical systems (such as catecholamines), the larger number of alterations that induce hyperactivity suggests a different scenario. Specifically, we hypothesize (i) the existence of a control system that continuously inhibit a basally hyperactive locomotor tone and (ii) that this control system is highly vulnerable (intrinsic fragility) to any change in the genetic asset or to any toxic/drug delivered during prepuberal stages. Brain lesion studies suggest that the putative control system is located along an axis that connects the olfactory bulb and the enthorhinal cortex (enthorhinal-hippocampal-septal-prefrontal cortex-olfactory bulb axis). We suggest that the increased locomotor activity in many psychiatric diseases may derive from the interference with the development of this brain axis during a specific postnatal time window.
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Affiliation(s)
- Davide Viggiano
- Department of Health Sciences, Faculty of Scienze del Benessere, University of Molise, Via De Sanctis III Edificio Polifunzionale, 86100 Campobasso, Italy.
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19
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Tõnissaar M, Herm L, Eller M, Kõiv K, Rinken A, Harro J. Rats with high or low sociability are differently affected by chronic variable stress. Neuroscience 2008; 152:867-76. [PMID: 18343596 DOI: 10.1016/j.neuroscience.2008.01.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 01/20/2008] [Accepted: 02/01/2008] [Indexed: 11/16/2022]
Abstract
Depression is strongly related to social behavior. We have previously shown that social behavior of rats is individually stable. The purpose of the present study was to compare the sensitivity of animals with different sociability to chronic variable stress (CVS). Four social interaction tests were performed with 60 single-housed male Sprague-Dawley rats. Twenty rats with the lowest and 20 with the highest average social activity time were selected as low sociability (LS) and high sociability (HS) rats, respectively. Both groups were further divided into control and stress groups with equal average body weight. The CVS procedure lasted for 3 weeks. The stressors applied were cold water and wet bedding, imitation of injection, stroboscopic light, movement restriction in a small cage, tail pinch with a clothespin, and strong illumination during the predicted dark phase. In HS-rats, but not in LS-rats, CVS reduced sucrose intake compared with baseline after 3 weeks, suggesting that HS-rats are more vulnerable to anhedonia elicited by CVS. LS-animals were more anxious in the social interaction and open field tests, but stress eliminated differences with HS-animals in the social interaction test and increased their activity in the forced swimming test. In LS-rats stress increased ex vivo dopamine levels and reduced 5-HT levels in the frontal cortex, suggesting that the increased behavioral activity after stress may be related to increased impulsivity. This study thus revealed that animals with high sociability trait are more vulnerable to anhedonia elicited by chronic stress in conditions of single housing.
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Affiliation(s)
- M Tõnissaar
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, EE-50410 Tartu, Estonia
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20
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Tõnissaar M, Mällo T, Eller M, Häidkind R, Kõiv K, Harro J. Rat behavior after chronic variable stress and partial lesioning of 5-HT-ergic neurotransmission: effects of citalopram. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:164-77. [PMID: 17826880 DOI: 10.1016/j.pnpbp.2007.08.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 07/27/2007] [Accepted: 08/06/2007] [Indexed: 01/07/2023]
Abstract
Deficits in serotonergic (5-HT-ergic) neurotransmission and stressful life events have been implicated in affective disorders, and chronic variable stress (CVS) can elicit behavioral changes reminiscent of increased emotionality, anxiety and atypical depression after partial 5-HT depletion. This study examined the effect of chronic citalopram treatment (10 mg/kg daily) on these changes. Parachloroamphetamine (PCA) (2 mg/kg) reduced the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the frontal cortex, increased anxiety in the social interaction test, and increased activity in the open field. CVS reduced social activity in the social interaction test and immobility time in the forced swimming test. Reduction of excrements left during immobilization indicated partial adaptation with the CVS. Specific stressors had different effects on body weight gain, shorter lasting stressors having a smaller effect in general than those that lasted longer. Combination of CVS and PCA increased sucrose intake after two weeks of stress. In addition, combination of the two treatments reduced diving in the forced swimming test. Citalopram prevented the increase in sucrose consumption in the PCA+CVS rats, and in 5-HT-depleted animals blocked the increase in struggling and reduced the number of defecations in the forced swim test. In conclusion, citalopram treatment prevented several effects of either 5-HT depletion or combined PCA+CVS treatment, suggesting that these behavioral changes could be used in studies on the neural mechanisms underlying emotional behavior that may have relevance to the neurobiology of depression.
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Affiliation(s)
- Margus Tõnissaar
- Department of Psychology, Center of Behavioral and Health Sciences, University of Tartu, Tiigi 78, EE-50410 Tartu, Estonia
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21
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Mällo T, Kõiv K, Koppel I, Raudkivi K, Uustare A, Rinken A, Timmusk T, Harro J. Regulation of extracellular serotonin levels and brain-derived neurotrophic factor in rats with high and low exploratory activity. Brain Res 2007; 1194:110-7. [PMID: 18177844 PMCID: PMC2568862 DOI: 10.1016/j.brainres.2007.11.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 11/19/2007] [Accepted: 11/25/2007] [Indexed: 12/02/2022]
Abstract
Serotonin (5-HT) system has a significant role in anxiety- and depression-related states and may be influenced by brain-derived neurotrophic factor (BDNF). This study examined extracellular 5-HT levels and expression of BDNF in rats with persistently low or high levels of exploratory activity (LE and HE, respectively). Baseline extracellular levels of 5-HT as assessed by in vivo microdialysis in conscious animals were similar in both groups in medial prefrontal cortex (PFC) and dentate gyrus (DG). No differences were found in parachloroamphetamine-induced 5-HT release in either region. However, LE animals had significantly higher levels of 5-HT transporter (5-HTT) binding in PFC and a larger increase in extracellular 5-HT levels after administration of citalopram (1 μM) into this area by retrograde dialysis. No difference in 5-HTT levels was found in hippocampus, while perfusion with citalopram was accompanied by a greater increase in extracellular 5-HT in the HE group in this brain region. LE-rats had higher levels of BDNF mRNA in the PFC but not hippocampus. In contrast, levels of nerve growth factor mRNA were similar in these brain regions of LE- and HE-rats. The differential regulation of 5-HT-ergic system in LE- and HE-rats in PFC and hippocampus may form the basis for their distinct anxiety-related behaviours.
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Affiliation(s)
- Tanel Mällo
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, 50410 Tartu, Estonia
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22
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Pérez V, Sosti V, Rubio A, Barbanoj M, Rodríguez-Alvarez J, Kulisevsky J. Modulation of the motor response to dopaminergic drugs in a parkinsonian model of combined dopaminergic and noradrenergic degeneration. Eur J Pharmacol 2007; 576:83-90. [PMID: 17888901 DOI: 10.1016/j.ejphar.2007.08.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 08/10/2007] [Accepted: 08/21/2007] [Indexed: 10/22/2022]
Abstract
Besides dopaminergic deficiency, other neurotransmitter systems such as noradrenergic nuclei are affected in Parkinson's disease. Locus coeruleus degeneration might influence the response to dopamine replacement and the presence of long-term complications such as dyskinesias. In this scenario of noradrenergic and dopaminergic neurodegeneration, behavioural effects induced by dopaminergic-interacting drugs are incompletely known. We investigated whether noradrenergic lesion modulates the levodopa (l-DOPA) response and modifies the response to adenosine antagonists and its interaction with l-DOPA. We examined the motor behaviour induced by: 1) subthreshold doses of l-DOPA (2mg/kg, i.p.), 2) the adenosine-receptor antagonist caffeine (10mg/kg), and 3) the combination of l-DOPA (2mg/kg) and caffeine (10mg/kg). Each study was done in two experimental conditions: a) rats with unilateral 6-OHDA lesion and b) rats with a lesion of the nigrostriatal pathway (6-OHDA) combined with selective denervation of locus coeruleus-noradrenergic terminal fields by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). While only 28% of the 6-OHDA-lesioned animals presented circling behaviour after l-DOPA challenge, all (100%) double-denervated animals rotated after the same l-DOPA dose (p<0.05). No statistical differences in the percentage of rotating animals were observed between single- and double-denervated rats after caffeine challenge. Combined l-DOPA-caffeine challenge produced rotational behaviour in all (100%) single- and double-denervated rats. No differences in total turns were observed between single- and double-denervated animals in each treatment condition. These findings suggest that additional noradrenergic denervation selectively decreases the motor threshold to l-DOPA treatment without modifying the magnitude or the pattern of the motor response to adenosinergic antagonism.
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Affiliation(s)
- Virgili Pérez
- Laboratori de Neuropsicofarmacologia, Institut de Recerca de l'Hospital de la Santa Creu i de Sant Pau, Avgda. St. Antoni M(a) Claret, 167, 08025 Barcelona, Spain
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23
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Mällo T, Alttoa A, Kõiv K, Tõnissaar M, Eller M, Harro J. Rats with persistently low or high exploratory activity: Behaviour in tests of anxiety and depression, and extracellular levels of dopamine. Behav Brain Res 2007; 177:269-81. [PMID: 17141886 DOI: 10.1016/j.bbr.2006.11.022] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/11/2006] [Accepted: 11/15/2006] [Indexed: 10/23/2022]
Abstract
Behaviour in novel environments is influenced by the conflicting motivators fear and curiosity. Because changes in both of these motivational processes are often simultaneously involved in human affective disorders, we have developed the exploration box test which allows separation of animals belonging to clusters with inherent high neophobia/low motivation to explore and low neophobia/high motivation to explore (LE and HE, respectively). In a novel home-cage, no behavioural differences were found between LE- and HE-rats, suggestive that it is not the general locomotor activity but specific features of the exploration box test that bring about the differences. In studies on both Wistar and Sprague-Dawley rats we found that the trait of exploratory activity remains stable over long periods of time and that LE and HE animals display differences in many other behavioural tests related to mood disorders. Namely, LE animals were found to display enhanced anxiety-like behaviour and to be generally less active in the elevated plus-maze, used more passive coping strategies in the forced swimming test, and acquired a more persistent association between neutral and stressful stimuli in fear conditioning test. LE animals consumed more sucrose solution in non-deprived conditions. We also found that both at baseline and in response to d-amphetamine (0.5mg/kg) administration, LE-rats had lower extracellular dopamine levels in striatum but not in nucleus accumbens. In conclusion, LE-rats appear more inhibited in their activity in typical animal tests of anxiety and are more susceptible to acute stressful stimuli.
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Affiliation(s)
- Tanel Mällo
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, Tartu 50410, Estonia
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24
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Matrov D, Kolts I, Harro J. Cerebral oxidative metabolism in rats with high and low exploratory activity. Neurosci Lett 2007; 413:154-8. [PMID: 17234343 DOI: 10.1016/j.neulet.2006.11.076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 11/16/2006] [Accepted: 11/22/2006] [Indexed: 11/30/2022]
Abstract
To reveal brain regions most significantly related to individual differences in exploratory behaviour, oxidative metabolism was measured by cytochrome c oxidase histochemistry in 2 months old Wistar rats with persistently high (HE) or low (LE) exploratory activity in a novel environment. LE-rats had significantly higher levels of oxidative metabolism in dorsal raphe and inferior colliculi. In contrast, HE-rats had higher metabolic activity in entorhinal cortex. In conclusion, rats with different exploratory styles differ in underlying cerebral activity as measured via oxidative metabolism in regions implicated in defensive behaviours and cognitive processing of sensory stimuli.
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Affiliation(s)
- Denis Matrov
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, EE-50410 Tartu, Estonia
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25
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Alttoa A, Eller M, Herm L, Rinken A, Harro J. Amphetamine-induced locomotion, behavioral sensitization to amphetamine, and striatal D2 receptor function in rats with high or low spontaneous exploratory activity: differences in the role of locus coeruleus. Brain Res 2006; 1131:138-48. [PMID: 17156751 DOI: 10.1016/j.brainres.2006.10.075] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 10/19/2006] [Accepted: 10/31/2006] [Indexed: 11/19/2022]
Abstract
Individual differences in novelty-related behavior are associated with sensitivity to various neurochemical manipulations. In the present study the amphetamine-induced locomotor activity and behavioral sensitization to amphetamine (0.5 mg/kg) was investigated in rats with high or low spontaneous exploratory activity (HE- and LE-rats, respectively) after partial denervation of the locus coeruleus (LC) projections with a low dose of the selective neurotoxin DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine; 10 mg/kg). DSP-4 produced a partial depletion (about 30%) of noradrenaline in the frontal cortex of both HE- and LE-rats; additionally the levels of metabolites of dopamine and 5-HT were reduced in the frontal cortex and nucleus accumbens of the LE-rats. Amphetamine-stimulated locomotor activity was attenuated by the DSP-4 pretreatment only in the HE-rats and this effect persisted over repeated testing. Behavioral sensitization to repeated amphetamine was evident only in the LE-rats with intact LC projections. Repeated amphetamine treatment reduced D(2) receptor mediated stimulation of [(35)S]GTPgammaS-binding and dopamine-dependent change in GDP-binding affinity in the striatum, but only in HE-rats. The absence of amphetamine sensitization in HE-rats could thus be related to the downregulation by amphetamine of the G protein stimulation through D(2) receptors. Conclusively, acute and sensitized effects of amphetamine depend on the integrity of LC projections but are differently regulated in animals with high or low trait of exploratory activity. These findings have implications to the neurobiology of depression, drug addiction, and attention deficit hyperactivity disorder.
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Affiliation(s)
- Aet Alttoa
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, 50410 Tartu, Estonia
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26
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Kalinin S, Feinstein DL, Xu HL, Huesa G, Pelligrino DA, Galea E. Degeneration of noradrenergic fibres from the locus coeruleus causes tight-junction disorganisation in the rat brain. Eur J Neurosci 2006; 24:3393-400. [PMID: 17229089 DOI: 10.1111/j.1460-9568.2006.05223.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although functional studies demonstrate that noradrenaline controls the permeability of the blood-brain barrier, it has never been determined whether this neurotransmitter regulates the tight junction (TJ) assembly that confers the barrier property to brain microvessels. We thus tested in rats the effect of pharmacological depletion of noradrenaline with the noradrenergic toxin DSP4 (5 mg/kg) on the expression of the TJ proteins zonula occludens-1 (ZO1) and occludin. The effectiveness of the lesion was confirmed by tyrosine hydroxylase immunoreactivity, which showed noradrenergic fibre reduction accompanied by debris and swollen fibres in DSP4-treated brains. Noradrenergic fibre degeneration caused: (i) gliosis; (ii) disappearance of TJ proteins in vascular cell-to-cell contacts (49.9 and 38.3% reductions for occludin and ZO1, respectively); (iii) a 49.2% decrease in total ZO1 protein, measured by Western blot analysis, parallel to a 39.5% decrease in ZO1 mRNA, measured by real-time PCR; and (iv) a relative increase in the beta occludin isoform (62.9%), with no change in total occludin protein or mRNA. The expression of endothelial brain antigen, a marker of a functionally competent brain endothelium, was also reduced. We conclude that damage to the ascending fibres from the locus coeruleus caused TJ disruption and gliosis, a sign of inflammation. These results imply that the locus coeruleus degeneration reported in Alzheimer's and Parkinson's diseases may contribute to these disorders by causing blood-brain barrier dysfunction. Whether the vascular damage is the result of impaired noradrenergic transmission or secondary to the inflammatory reaction remains to be determined.
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Affiliation(s)
- Sergey Kalinin
- Department of Anaesthesiology, University of Illinois at Chicago, Illinois, USA
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27
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Tõnissaar M, Herm L, Rinken A, Harro J. Individual differences in sucrose intake and preference in the rat: Circadian variation and association with dopamine D2 receptor function in striatum and nucleus accumbens. Neurosci Lett 2006; 403:119-24. [PMID: 16682119 DOI: 10.1016/j.neulet.2006.04.023] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 04/17/2006] [Accepted: 04/19/2006] [Indexed: 10/24/2022]
Abstract
Measurement of sucrose intake or preference is currently in widespread use in preclinical psychopharmacology, and used for predicting sensitivity to rewards, but limited information is available about the consistency of individual sucrose intake or preference. In the present study, individual differences in sucrose intake and preference in free-feeding rats were studied during the dark and light phases, and associations of these measures with the function of D(2) receptors in the striatum and nucleus accumbens were characterized. Altogether eight two-bottle tests were carried out intermittently during light and dark phase. Ten days after the last test, animals were sacrificed. Intake, and to a lesser degree preference of sucrose during the dark phase were higher as compared to the light phase, and sucrose intake, but not preference was individually very consistent across different tests, especially during the dark phase. The average dark phase sucrose intake and preference correlated positively with dopamine-dependent [(35)S]GTPgammaS binding in nucleus accumbens. Dopamine-dependent [(35)S]GTPgammaS binding in striatum correlated negatively with sucrose preference in the first test. This study has demonstrated that sucrose intake is an individually stable trait, especially when measured during the dark phase, and persistent individual differences in sucrose consumption and possibly reward sensitivity in general are related to dopamine D(2) receptor function in the nucleus accumbens. Individual differences in D(2) receptor function in the striatum may influence behaviour of rats in novel situations.
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Affiliation(s)
- Margus Tõnissaar
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tiigi 78, EE-50410 Tartu, Estonia
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