Banca de DEFESA: ISABELLA MARIA DE OLIVEIRA PONTES FERNANDES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ISABELLA MARIA DE OLIVEIRA PONTES FERNANDES
DATE: 12/11/2019
TIME: 14:00
LOCAL: Sala Darwin
TITLE:
KEY WORDS:

stress, depression, memory, fear, sexual differences, fluoxetine, forced swimming.

PAGES: 148
BIG AREA: Ciências Humanas
AREA: Psicologia
SUMMARY:

Stress is characterized by physical and psychological changes triggered by external and internal pressures. Repeated exposure to stressful events promotes changes in an individual's cognitive, emotional, and behavioral processes, and such changes may be related to mental illness such as depression. Studies point to different stress coping strategies and data from the World Health Organization show that the incidence of depression and the response to antidepressant treatment are different between men and women and that this difference is related to the hormonal cycling that occurs in females. In addition, stress-induced cognitive changes and response to treatment in males and females are distinct, especially memories with emotional context, which are known to be directly influenced by sex hormones, and are still related to the mechanism of action of antidepressants used in the clinical practice, such as fluoxetine (FLX). However, most studies are conducted on males with the excuse that hormonal variation makes female analysis even more complex. Understanding the sexual differences in stress response in males and females is essential to prevent and treat pathologies that may arise from stress more effectively, looking up to the particularities of each individual. In this sense, we submitted male and female Wistar rats to the model of chronic mild stress (CMS), widely used to induce depressive-like behavior in animals, to investigate possible behavioral changes related to depression and fear memory, and its response to FLX treatment. At first, two pilot experiment were held to establish the time required to animals present depressive-like behavior and the moment of treatment beginning. The animals were submitted to 35 days of CMS and treated in the last 14 days with FLX or its vehicle (VEH), and were submitted to forced swimming (FST), open field (OF) and splash test (ST) before and after the FLX treatment, and contextual fear conditioning (CFC) at the end of the protocol. Females were separated by estrous cycle phases with high (proestrus and estrus - P/E) and low (metaestrus and diestrus - M/D) hormonal levels. Our data demonstrate that before treatment (TTT) only male-CMS showed depressive-like behavior represented by increased immobility time in FST compared to male-control (CTR), but not after TTT possibly because immobility memory retention impairment. After TTT femalesCMS showed increased climbing time, independent of FLX, and P/E-CTR showed reduced immobility time and increased active time compared to M/D-CTR, suggesting that estrogen may have an antidepressant effect. Also, CMS-FLX showed reduced immobility and increased active time compared to M/D-CTR-FLX but not P/E-CTR-FLX and CMS-VEH. In ST, male-CMS showed increased grooming time compared to male-CTR before TTT and male-CMS-VEH showed increased grooming time compared to male-CTR-VEH and after TTT. After TTT female-CTR-FLX showed reduced grooming time compared to female-CMS-FLX, showing conflicting results to literature. The animals of both sexes showed no differences in locomotor activity in OF, demonstrating that the effects observed in the other tests were not due to locomotion impairment. P/E-CMS explored less the center of the field than its CTR, suggesting an anxiogenic effect, possibly mediated by estrogen. In CFC male-CMS showed reduction in freezing time compared to CTR, regardless of treatment with FLX, suggesting impairment in fear memory caused by CMS only in male. In conclusion, our data show sex differences of CMS in response to FST and CFC. Male rats demonstrated to be more vulnerable to CMS exhibiting depressive-like behavior earlier than females and also fear memory impairment. On the other hand, female express depressive-like behaviors in phases of estrous cycle with low hormone levels (M/D) and high levels of hormones (increased estrogen) may have protective effect in females in depressive like behavior after chronic stress but no impact on fear memory.

BANKING MEMBERS:
Externo à Instituição - EZEQUIEL BATISTA DO NASCIMENTO
Externo à Instituição - RAMÓN HYPOLITO LIMA - IINN
Presidente - 2140860 - ROVENA CLARA GALVAO JANUARIO ENGELBERTH
Externa ao Programa - 1720860 - VANESSA DE PAULA SOARES RACHETTI
Interno - 089.072.754-67 - VICTOR ANASTÁCIO DUARTE HOLANDA - UFRN