Effects of oxidative stress on development of behavioral sensitization in Drosophila melanogaster

Povećanje dopaminske neurotransmisije inducirano psihostimulansima predstavlja jedan od inicijalnih faktora za razvoj ovisnosti. Budući da oksidativni metabolizam dopamina stvara reaktivne kinone i slobodne radikale, istraživanja sugeriraju da oksidativni stres ima utjecaja na bihevioralne promjene uključujući lokomotornu senzitizaciju. Istraživanja na glodavcima su pokazala kako administracije kokaina (COC) ili metamfetamina (METH) povećavaju oksidativne markere u regiji mozga koja je važna za ekspresiju lokomotorne senzitizacije. Svrha diplomskog rada je definirati ulogu povećanog i smanjenog oksidativnog statusa na razvoj lokomotorne senzitizacije na modelnom organizmu vinske mušice (Drosophila melanogaster). Mušice su prehranom tretirane s prooksidansima i/ili antioksidansima prije i tijekom administracije volatiliziranog COC ili METH te su praćene promjene u lokomotornoj aktivnosti. Administrirane su dvije iste doze psihostimulansa kroz određeni vremenski interval kako bi pratili razvoj lokomotorne senzitizacije. Mjerenjem oksidativnih markera (aktivnost katalaze CAT i superoksid dismutaze SOD; koncentracija vodikovog peroksida H2O2 i superoksidnog anion radikala O2●- ) ispitivali smo kako smanjenje ili povećanje oksidativnog statusa inducirano tretmanom s prooksidansima i antioksidansima dovodi do promjena u lokomotornoj aktivnosti na ponovljene administracije psihostimulansa. Razvoj lokomotorne senzitizacije na COC i METH je spriječen kod mušica tretiranih antioksidansima, kao i kod mušica tretiranih s prooksidansima. Dodatno, pokazali smo da kombinirani tretman s prooksidansima i antioksidansima dovodi do obnavljanja lokomotorne senzitizacije na METH. Mjerenjem parametara oksidativnog statusa uočili smo razlike između tretmana, kao i razlike između COC i METH. Naši rezultati sugeriraju da egzogena primjena prooksidansa ili antioksidansa dovodi do promjena u oksidativnom statusu što se očituje na sprječavanje lokomotorne senzitizacije. Identifikacija promjena u oksidativnom statusu koje dovode do promjena u bihevioralnom odgovoru će pomoći objasniti kompleksnost mehanizama ovisnosti te poticati razvoj učinkovitih terapija za svladavanje ovisnosti.Psychostimulants induced increase in dopamine neurotransmission is considered to be one of the initial factors for the development of addiction. Since oxidative metabolism of dopamine produces reactive quinones and free radicals, studies suggest that oxidative stress has implications for behavioral changes including locomotor sensitization. Research on rodents has shown that administration of cocaine (COC) or methamphetamine (METH) increases oxidative markers in the brain region which is important for expression of locomotor sensitization. The purpose of the master thesis is to define the role of increased and decreased oxidative status on the development of locomotor sensitization in fruit fly (Drosophila melanogaster). Flies were fed with pro-oxidants and/or antioxidants before and during administration of volatilized COC or METH and changes in locomotor activity were examined. To monitor the development of locomotor sensitization, two doses of psychostimulant were administered over a certain time interval. By measuring oxidative markers (activity of catalase CAT and superoxide dismutase SOD; concentration of hydrogen peroxide H2O2 and superoxide anion radical O2●-), we investigated how decrease or increase in oxidative status, induced by pro-oxidant or antioxidant treatment, leads to changes in locomotor activity after repeated administration of psychostimulants. Locomotor sensitization to COC and METH is abolished in flies treated with antioxidants, as well as in flies treated with pro-oxidants. In addition, we report that combined treatment with pro-oxidants and antioxidants restores locomotor sensitization to METH. We observed differences between treatments, as well as differences between COC and METH. Our results suggest that the exogenous exposure to pro-oxidants or antioxidants results in changes in oxidative status, which is evident in the abolished locomotor sensitization. Identifying changes in oxidative status that lead to changes in behavioral response will help explain the complexity of addiction mechanisms and encourage the development of effective therapy for addiction