129Sv ja C57/Bl6 hiireliinide erinevad stressiga toimetuleku strateegiad – viited käitumuslikest, farmakoloogilistest, metaboloomika ja geeniekspressiooni uuringutest

Väitekirja elektrooniline versioon ei sisalda publikatsioonePrekliinilistes uuringutes on kõige laialdasemalt kasutatavaks mudelorganismiks laborihiir (Mus musculus domesticus). Põhjuseks on asjaolu, et hiired on inimestega geneetiliselt ja bioloogiliselt piisavalt sarnased. Kõige levinumad hiireliinid biomeditsiinilistes uuringutes on C57/Bl6 (Bl6) ja 129Sv. Käesolev doktoritöö annab ülevaate kahe hiireliini – 129Sv ja Bl6 – erinevustest, mis aitab teadlastel paremini valida konkreetse uurimisülesande lahendamiseks vajalikku hiireliini. Käitumiskatsed näitasid Bl6 hiirte suuremat liikumisaktiivsust. Seejärel vaadeldi ühekordse ja korduva amfetamiini manustamise mõju liikumisaktiivsusele. Amfetamiini rakendatakse prekliinilistes uuringutes psühhootiliste seisundite alusmehhanismide uurimise vahendina. Tulemusena leiti, et Bl6 hiired, kes said amfetamiini ühekordselt, liikusid võrreldes 129Sv hiirtega palju rohkem. Korduv amfetamiini manustamine suurendas liikumisaktiivsust palju enam 129Sv liinis. Tõsi, mitte kõigil 129Sv hiirtel, sest pooltel grupi loomadel jäi läbitud distants samale tasemele ühekordse manustamisega. Ka inimpopulatsioonis ilmneb sarnane mõju erinevus – osal tekib amfetamiini võimsama analoogi metamfetamiini mõjul sõltuvus, teistel aga kujuneb raske psühhoos. Metaboloomika uuringud näitasid, et Bl6 hiirtel on motoorse testiga kohanemisel eelkõige aktiveerunud suhkrutega seotud metabolismirajad, kuid 129Sv hiirtel domineeris rasvade metabolism. Arvestades hiirte käitumuslikku reageerimist amfetamiinile ja geeniekspressiooni tulemusi, võib järeldada, et Bl6 hiirte ajustruktuurides on dopaminergilise süsteemi aktiivsus suurem kui 129Sv hiirtel. Valguekspressiooni uuringute põhjal võivad EGF, ERBB1 ja GRIN1 olla need otsmikukoore biomarkerid, mis on seotud parema kohanemisega Bl6 hiirtel. Kokkuvõttes võib väita, et Bl6 hiireliin näib olevat sobivam uimastisõltuvuse mehhanismide uurimiseks ning 129Sv hiireliin pakub paremaid võimalusi depressiooni- ja psühhoosilaadsete seisundite selgitamiseks.The most widely used animal model in preclinical studies is the laboratory mouse (Mus musculus domesticus) because they are similar to humans, both genetically and biologically. The most common mouse strains in biomedical applications are C57/Bl6 (Bl6) and 129Sv. The dissertation provides an overview of the differences between the two strains - 129Sv and Bl6 - which would allow researchers to better choose the line required to solve a specific research task. The study showed higher behavioral activity of Bl6 line. Thereafter, the effect of amphetamine on locomotor activity was evaluated. Amphetamine treatment is applied in preclinical settings to investigate the basic mechanisms of psychotic conditions. Bl6 mice receiving acute (one time injection of) amphetamine displayed significantly higher motor activity compared to 129Sv mice. However, repeated administration of amphetamine elevated activity more in the 129Sv line, but not in all animals, as in half of the mice the activity remained the same as in acute administration group. A similar effect is present in human population where methamphetamine causes in some individuals addiction, but others develop psychosis. The metabolomic studies revealed that in adaptation to the environment, Bl6 mice use glucosis-related pathways whereas the 129Sv line tends to favor lipid metabolism. Based on the behavioural response of mice to amphetamine and the gene expression studies, it was concluded that the activity of the dopaminergic system in the brain of Bl6 mice is higher than that of 129Sv mice. Furthermore, studies of protein expression suggested that EGF, ERBB1 and GRIN1 in the frontal cortex may be the biomarkers related with better environmental adaptation. In conclusion, the Bl6 mouse line seems to be more suitable for elucidating the mechanisms of drug dependence, and 129Sv mice offer better opportunities to investigate depression and psychosis-like conditions.https://www.ester.ee/record=b553080

Dopamine System, NMDA Receptor and EGF Family Expressions in Brain Structures of Bl6 and 129Sv Strains Displaying Different Behavioral Adaptation

C57BL/6NTac (Bl6) and 129S6/SvEvTac (129Sv) mice display different coping strategies in stressful conditions. Our aim was to evaluate biomarkers related to different adaptation strategies in the brain of male 129Sv and Bl6 mice. We focused on signaling pathways related to the dopamine (DA) system, N-methyl-D-aspartate (NMDA) receptor and epidermal growth factor (EGF) family, shown as the key players in behavioral adaptation. Mice from Bl6 and 129Sv lines were divided into either home cage controls (HCC group) or exposed to repeated motility testing and treated with saline for 11 days (RMT group). Distinct stress responses were reflected in severe body weight loss in 129Sv and the increased exploratory behavior in Bl6 mice. Besides that, amphetamine caused significantly stronger motor stimulation in Bl6. Together with the results from gene expression (particularly Maob), this study supports higher baseline activity of DA system in Bl6. Interestingly, the adaptation is reflected with opposite changes of DA markers in dorsal and ventral striatum. In forebrain, stress increased the gene expressions of Egf-Erbb1 and Nrg1/Nrg2-Erbb4 pathways more clearly in 129Sv, whereas the corresponding proteins were significantly elevated in Bl6. We suggest that not only inhibited activity of the DA system, but also reduced activity of EGF family and NMDA receptor signaling underlies higher susceptibility to stress in 129Sv. Altogether, this study underlines the better suitability of 129Sv for modelling neuropsychiatric disorders than Bl6

Depression-Associated <i>Negr1</i> Gene-Deficiency Induces Alterations in the Monoaminergic Neurotransmission Enhancing Time-Dependent Sensitization to Amphetamine in Male Mice

In GWAS studies, the neural adhesion molecule encoding the neuronal growth regulator 1 (NEGR1) gene has been consistently linked with both depression and obesity. Although the linkage between NEGR1 and depression is the strongest, evidence also suggests the involvement of NEGR1 in a wide spectrum of psychiatric conditions. Here we show the expression of NEGR1 both in tyrosine- and tryptophan hydroxylase-positive cells. Negr1−/− mice show a time-dependent increase in behavioral sensitization to amphetamine associated with increased dopamine release in both the dorsal and ventral striatum. Upregulation of transcripts encoding dopamine and serotonin transporters and higher levels of several monoamines and their metabolites was evident in distinct brain areas of Negr1−/− mice. Chronic (23 days) escitalopram-induced reduction of serotonin and dopamine turnover is enhanced in Negr1−/− mice, and escitalopram rescued reduced weight of hippocampi in Negr1−/− mice. The current study is the first to show alterations in the brain monoaminergic systems in Negr1-deficient mice, suggesting that monoaminergic neural circuits contribute to both depressive and obesity-related phenotypes linked to the human NEGR1 gene