title: Chronic variable stress prevents amphetamine-elicited 50-kHz calls in rats with low positive affectivity.
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.
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
authors.forename: Kadri
authors.initials: K
authors.lastname: Kõiv
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
authors.forename: Mait
authors.initials: M
authors.lastname: Metelitsa
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
authors.forename: Marten
authors.initials: M
authors.lastname: Vares
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
authors.forename: Kai
authors.initials: K
authors.lastname: Tiitsaar
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia.
authors.forename: Karita
authors.initials: K
authors.lastname: Raudkivi
authors.affiliation: Department of Pharmacology, Institute of Biomedicine and Translational Medicine, University of Tartu, Ravila 19, 50411 Tartu, Estonia.
authors.forename: Külli
authors.initials: K
authors.lastname: Jaako
authors.affiliation: Department of Natural Sciences, School of Natural Sciences and Health, Tallinn University, Narva 29, 10120 Tallinn, Estonia.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Vulla
authors.affiliation: Department of Natural Sciences, School of Natural Sciences and Health, Tallinn University, Narva 29, 10120 Tallinn, Estonia.
authors.forename: Ruth
authors.initials: R
authors.lastname: Shimmo
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Ravila 14 A, 50411 Tartu, Estonia. Electronic address: jaanus.harro@ut.ee.
authors.forename: Jaanus
authors.initials: J
authors.lastname: Harro
mesh_terms: D000339:Affect; D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D003913:Dextroamphetamine / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism; D005518:Food Preferences / Q000187:drug effects; D005625:Frontal Lobe / Q000378:metabolism; D007532:Isoleucine / Q000378:metabolism; D008124:Locomotion / Q000187:drug effects; D008297:Male; D009714:Nucleus Accumbens / Q000378:metabolism; D051381:Rats; D017447:Receptors, Dopamine D1 / Q000378:metabolism; D013239:Stereotyped Behavior / Q000187:drug effects; D013315:Stress, Psychological / Q000378:metabolism* / Q000523:psychology*; D013395:Sucrose / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D014828:Vocalization, Animal / Q000187:drug effects*
chemical_list: D015306:Biogenic Monoamines; D017447:Receptors, Dopamine D1; D007532:Isoleucine; D013395:Sucrose; D003913:Dextroamphetamine; D004298:Dopamine
keywords: 50-kHz vocalizations; Amphetamine; Chronic stress; Isoleucine; Monoamines; Positive affectivity