Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.


DATA: 30/09/2010

LOCAL: Anfiteatro das Aves

Transmissão gabaérgica na amígdala durante aprendizado aversivo e extinção de memórias em ratas


amygdala, estrus cycle, extinction, GABA.


GRANDE ÁREA: Ciências Humanas

ÁREA: Psicologia

SUBÁREA: Psicologia Fisiológica

ESPECIALIDADE: Psicobiologia


BACKGROUND: GABA neurotransmission suffers an intricate and continuous plasticity mediated by stress, gonadal hormones oscillations and modulation by canabinoids and opioids, among others. This system has been implicated in several aspects of mood disorders and memory and learning, especially in aversive memory extinction. The amygdala is an essential structure for emotional memory modulation and it has been one of the major focuses for research on GABAergic participation on memory. Most of the animal studies on this issue are held with male subjects, but there is evidence that female mice have an increased GABAergic transmission when in proestrus or estrus (j.psyneuen. 34:84,2009).

OBJECTIVE: In the present study, we investigate the consequences of an increased or reduced GABAergic transmission in the amygdala on aversive memory retrieval and extinction in female rats in proestrus and estrus.

METHODS AND RESULTS: Three-month old females Wistar rats about 230g were implanted with bilateral cannula aimed at the basolateral amygdala (BLA). Estrous cycle phase was determinated by vaginal cytology for two weeks before behavioral tests and experiments were scheduled so that females were in proestrus or estrus during test (day 2 of experiment). We used the discriminative avoidance task in the elevated plus-maze to access memory retrieval and extinction. During training the animals learned to avoid one of the closed arms, in which they receive an aversive stimulus, consisting of a bright light and a loud noise. Fifteen minutes before the test session (held 24h later) animals received bilateral intra-amygdala 0,2 µL injections of saline (control),  GABAR agonist muscimol (0,05 mg/ml) or  the GABAR antagonist bicuculline (0,025mg/ml). As expected animals showed acquisition of the task, indicated by the lower relative time in aversive arm (TAV%) during the final minutes compared to the initial minutes of training (1st-3rd min: 8,05±1,18;  8th-10th min: 0,71±0,27). No differences between groups were observed during test when taking proestrus and estrus together for anaysis. However, when phases were considered separately groups exhibited unexpected differences. In saline-treated group, only animals that were in estrus during test showed task extinction (Estrus - 8th-10th min: 64,68±21,28; proestrus - 8th-10th min : 14,68±10,72). Compared to saline group, both drug treated groups in estrus presented impaired extinction (bicuculline - 8th-10th min: 15,87±9,50 and muscimol - 8th-10th min: 39,13±5,63). On the other hand, both drug treated animals in proestrus had their extinction improved compared to saline group (bicuculline -  8th-10th min: 37,68±24,77 and  muscimol - 8th-10th min: 19,21±8,98).

CONCLUSION: The opposite effects presented by drugs according to estrous cycle phase, as well as the similarity of the effects induced by GABAR agonist or antagonist in each phase, indicate that the interaction between gonadal hormonal cycle, amygdal GABAergic transmission and memory is complex. In addition, behavioral profiles showed in proestrus and estrus phases seem to be less similar than suggested by previous studies. More studies will be necessary to confirm those results and shed light into this intricated relationship.

Financial support: CNPq, CAPES, PROPESQ-UFRN

Presidente - 1439078 - REGINA HELENA DA SILVA
Notícia cadastrada em: 20/09/2010 17:51
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