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Previous issue date: 2017-12-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The present study investigated if the model of memory dysfunction induced by iron overload, so far only tested in male rats, would be able to induce cognitive decline in female rats, aiming to validate it as an experimental model to study gender differences in neurodegenerative diseases. We also evaluated the effects of the activation of the G protein coupled estrogen receptor (GPER) on iron- and ovariectomy-induced memory deficits and the role of the PKA/CREB pathway as a mediator of its physiologic effects. Four experiments were performed: I ? female rats received iron (30mg/kg, per oral, p.o.) or vehicle (sorbitol, p.o.) in the neonatal period and after, in adulthood, they were submitted to the surgical protocol: ovariectomy (OVX) or false-surgery (SHAM), after 3 weeks, behavioral tasks were performed using the object recognition (RO); object location (OL) and inhibitory avoidance (IA) tasks; II ? the same two protocols cited before and behavioral tasks 3 weeks from the surgeries, but, immediately after the training sessions the animals received the selective agonist of the GPER, G1 (10mg/kg, subcutaneously, sc.) or vehicle (veh, oil, sc.), the long-term memory was assessed 24h after the training sessions; III ? dose-response curve in order to determine the the effects of the PKA-inhibitor (H-89) on memory retention of inhibitory avoidance task, the following doses were administered intraperitoneally to na?ve adult female rats: 0.1 mg/kg; 0.25mg/kg or 0.5mg/kg; and finally the experiment IV in which the memory of iron overloaded-ovariectomized female rats was assessed 24h after that they had received H-89 (0.25mg/kg, ip.) or veh 15 minutes previous to the training sessions and G1 (10mg/kg, sc.) or veh immediately after their training in the OL and IA tasks. We observed that the effects of iron overload in female, associated or non-associated to OVX varied according to the behavioral test that the animals were submitted. The lowest recognition index level in OL task was observed in the animals exposed to the iron overload and, subsequently, to the lack of estrogens secondary to ovariectomy. The acute post-training treatment with G-1 increased the recognition index in the OL task and it was also associated with an increasing in the latency to step down ifrom the platform to the grid in the IA task. Finally, all these positive results obtained with the post-training administration of G-1 were abolished when the animals received the pre-training treatment of H-89. Our study opens new avenues in the field of memory and estrogens once it introduces the association of lack of estradiol and iron overload as a pre-clinical phenotypical model of the aging process in women. Besides, from the best of our knowledge, it is the first evidence of the role of the G1 in the consolidation of the emotional memory as well as the first study connecting the GPER directly to the PKA/CREB pathway. / Este estudo investigou se o modelo de disfun??o cognitiva induzido pela sobrecarga de ferro, somente testado em ratos machos at? o momento, induz d?ficits de mem?ria em ratas, objetivando valid?-lo como um m?todo experimental que auxilie na compreens?o das diferen?as fisiopatol?gicas entre os sexos em rela??o ?s doen?as neurodegenerativas. Tamb?m avaliamos, de maneira in?dita, os efeitos da ativa??o receptor de estrog?nio acoplado ? prote?na G (GPER), nesse modelo combinado com o modelo de menopausa experimental. Al?m disso, especulamos o papel da via da PKA/CREB na ativa??o do GPER, atrav?s da inibi??o farmacol?gica da PKA. Foram realizados quatro experimentos para atingir esses objetivos: I ? ratas tratadas com ferro (via oral ? v.o.) ou ve?culo (sorbitol ? v.o.) foram ovariectomizadas ou submetidas ? cirurgia falsa (SHAM) na idade adulta, ap?s tr?s semanas do protocolo cir?rgico foram submetidas ?s tarefas de reconhecimento de objetos (RO), localiza??o de objetos (LO) e esquiva inibit?ria (EI); II ? ratas tratadas com ferro no per?odo neonatal foram ovariectomizadas ou submetidas ? cirurgia SHAM, ap?s recupera??o da cirurgia (3 semanas) foram tratadas anteriormente aos treinos das tarefas de LO e EI com G-1 (agonista seletivo do GPER, 10mg/kg, sc.) ou ve?culo (?leo de girassol, sc.) e testadas 24h ap?s o treino; III ? ratas naive receberam diferentes doses do composto H-89 (inibidor da PKA) para avaliar seu potencial amn?sico (0.1mg/kg, 0.25mg/kg e 0.5mg/kg; ip.) e IV ? ratas submetidas ? sobrecarga neonatal de ferro e OVX, ap?s 3 semanas do protocolo cir?rgico receberam quinze minutos antes dos treinos das tarefas de LO e EI o composto H-89 (0.25mg/kg, ip.) ou ve?culo (salina, ip.) e imediatamente ap?s o treino G-1 (10mg/kg, sc.) ou ve?culo (?leo de girassol, sc.), as ratas foram testadas ap?s 24h dos treinos. Os efeitos do protocolo de sobrecarga neonatal de ferro associado ou n?o a priva??o de estradiol variou em depend?ncia da tarefa comportamental avaliada. Na tarefa de LO os grupos submetidos ? sobrecarga neonatal de ferro e ovariectomia apresentaram os menores ?ndices de reconhecimento. O tratamento com o agonista do GPER ? G1 - foi capaz de melhorar os d?ficits cognitivos induzidos pela sobrecarga neonatal de ferro e/ou pela ovariectomia em ratas no teste de LO e EI, esses efeitos foram inibidos pela administra??o do inibidor da PKA anteriormente ao treino das tarefas. Demonstramos que o modelo de sobrecarga neonatal de ferro associado ? ovariectomia ? um modelo ?til para o estudo dos efeitos delet?rios da diminui??o dos n?veis s?ricos de estradiol na menopausa, auxiliando como modelo fenot?pico do que ocorre na cl?nica, onde as mulheres p?s-menopausa apresentam preval?ncia maior de Doen?a de Alzheimer que homens. Al?m disso, demonstramos de maneira in?dita os efeitos do composto G-1 na tarefa de esquiva inibit?ria. Nossos dados comportamentais tamb?m sugerem que o composto G-1 depende da ativa??o da PKA para exercer seus efeitos sobre a consolida??o da mem?ria.
| Identifer | oai:union.ndltd.org:IBICT/oai:tede2.pucrs.br:tede/8236 |
| Date | 28 December 2017 |
| Creators | Machado, Gustavo Dalto Barroso |
| Contributors | Schroder, Nadja |
| Publisher | Pontif?cia Universidade Cat?lica do Rio Grande do Sul, Programa de P?s-Gradua??o em Medicina e Ci?ncias da Sa?de, PUCRS, Brasil, Escola de Medicina |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da PUC_RS, instname:Pontifícia Universidade Católica do Rio Grande do Sul, instacron:PUC_RS |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 7620745074616285884, 500, 500, 500, 600, -224747486637135387, -969369452308786627, 2075167498588264571 |
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