RESUMO
Age-related impairment in synaptic plasticity, like long-term potentiation (LTP), has been repeatedly reported. We had shown that late stages of LTP in the rat dentate gyrus can be modulated by emotional factors, but this is impaired by aging. In the present study we have searched for possible impairments in emotional and spatial memory tasks that may correspond to the impaired reinforcement observed at the cellular level. We have trained young and aged animals in a battery of tests: exploration (open field) object recognition, anxiety (plus maze) fear conditioning and spatial memory (Morris' water maze (MWM)). The open field, anxiety, and novelty recognition showed no age differences except a reduced velocity in aged rats. Emotional and contextual memories were preserved, but acquisition was slightly impaired. Age-dependent impairments appeared in spatial memory, evaluated in terms of latency and distance to reach the hidden escape platform in the water maze task, but these were not related with impairments in other tests, in particular there was no relation between spatial and emotional memory impairments. Age-related impairments in different paradigms were caused by different independent factors that did not correlated with each other.
Assuntos
Envelhecimento/fisiologia , Encéfalo/fisiopatologia , Avaliação da Deficiência , Transtornos da Memória/fisiopatologia , Transtornos do Humor/fisiopatologia , Animais , Causalidade , Modelos Animais de Doenças , Masculino , Transtornos da Memória/diagnóstico , Transtornos da Memória/etiologia , Modelos Estatísticos , Transtornos do Humor/diagnóstico , Transtornos do Humor/etiologia , Ratos , Ratos WistarRESUMO
INTRODUCTION: Numerous reports show that lesions to hippocampus afferents, such as the entorhinal cortex (EC) and the fimbria fornix (FF), exert an effect on memory in rodents. There are, however, no long term comparative studies that show which of these lesions could be most useful as a model for studies into neuroplasticity. MATERIAL AND METHODS: Young male Sprague Dawley rats were used. Bilateral electrolytic lesion was caused to the EC or the FF was damaged by transection. One, four or 12 weeks later the animals were evaluated in a Morris water maze, first with an invisible platform and then with the platform within view. The results from the two groups were compared to each other and to those obtained from healthy controls and subjects with false lesions by means of a variance analysis. RESULTS: In the test with an invisible platform, both types of lesion gave rise to serious, irreparable involvement of the spatial memory of the animals, at least up to 12 weeks after the lesion. The test with the visible platform revealed significant differences between animals with lesion to the EC evaluated at 12 weeks, which suggests the development of some visual or motor deterioration in these animals. CONCLUSIONS: Although both lesions gave rise to behavioural deterioration that was irreversible in the long term in rodents, the lesion to the FF seems to be a better model for evaluating specific effects on learning and memory, since the lesion to the EC apparently triggers additional sensory and motor involvement.