Prejuízo de memória do tipo episódica induzido pela Cetamina: diferenças funcionais na expressão de c-Fos em sub-regiões do hipocampo

• Autor(a) principal: Souza, Ingrid Brasilino Montenegro Bento de
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/7750
• topic: Memória do tipo episódica; Episodic-like memory; Ketamine; Cetamina; c-Fos; CIENCIAS HUMANAS::PSICOLOGIA

Episodic-like memory is a subtype of declarative memory that refers recall an integration of where and when a certain event (what) happened. The hippocampus –subregions function in pattern separation process are key to mediating of episodic memory recall. Glutamatergic neurotransmission, particularly AMPA and NMDA receptors, have been characterized as essential in neuroplastic processes. Ketamine is a non-competitive NMDA antagonist available at clinical practice with effect on cognitive performance and plasticity. This study’s goal was to evaluate the acute action of ketamine on behavioral and neurochemical aspects of episodic-like memory through immediate-early gene expression (IEG), c-Fos. The experimental procedure was done at a circular arena, and consists of two training sessions and a test of five minutes each. In the first training, the animal was placed in a circular open field to explore four similar objects (A), after a 1 hour, the rats start a second sample with four other objects (B), two of those appear in different spatial locations relative for the first sample. In the test, four objects are shown, two recent-familiar (B) and two old-familiar (A), two displaced (A2, B2) and two stationary (A1 and B1). Forty-six 3-month-old male Wistar rats were separated in five groups. The home cage group (n=6; without apparatus exposure) was used to measure IEG basal expression. The other four groups, with 10 rats each, went through the behavioral test. One of them received saline 0.9% and the other two received 8 mg/kg or 15 mg/kg ketamine ip immediately after the second sample, while the control group received no treatment. All objects and spatial location in this protocol were randomized among groups. The analyses were blinded for groups and the behavioral measures were distance, speed and time of exploration in all sessions. The exploration ratio and discrimination ratio of the four objects in the test session were calculated. Wilcoxon test showed statistically significant differences between these pairs of objects in the control group: A1> A2, B2> B1 and A1> B1. The data indicate that these rats could integrate the three elements of episodic-like memory. The saline group demonstrated the same exploration pattern of control group for comparisons between A1>A2 and B2>B1, but statistical differences were not found between A1and B1. The Welch’s analysis showed a difference of c-Fos expression in all hippocampal sub-regions. The control group had the highest c-Fos expression in the dentate gyrus when compared to the other groups, suggesting the role of this sub-region for integration of episodic-like memory. The two sub-anesthetic doses of ketamine induced a deficit for this type of memory. The highest dose demonstrated a possible hypolocomotion effect, characterized by decreasing of total distance traveled and speed, compared to the other groups at the test session. In short, the deficit of episodic-like memory was characterized both as amnesic effect of ketamine and as decrease of c-Fos in the dentate gyrus of those groups, suggesting a possible role of this field in episodic-like memory formation.