Desnutrição protéica precoce prejudica memória de ratos testados em diferentes procedimentos de reconhecimento de objetos (Rattus norvegicus)

Abstract

BRAGA, N. N. Early protein malnutrition affects memory of rats tested in several procedures of object recognition (Rattus norvegicus). Master Thesis – Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto. Universidade de Sao Paulo. 2010, 83f. Early Postnatal protein malnutrition affects structures involved in the mechanisms of behavior, learning and memory. Thus, the aim of this work was to evaluate the performance of malnourished rats in several procedures of recognition memory for objects. Male Wistar rats (n=132) were submitted to isocaloric diets containing 6% (Malnourished) or 16% of protein (Control) during the first 49 days of life. A nutritional recovery period was imposed from 50 to 70 days of age, when behavioral tests started. In the Experiment I the animals were put in an open field with an object A. After 3 or 24 hours of this exposition, the rat returned in the open field with the object A and another object B. The Experiment II was conducted with three different procedures. In the first one, the animal was placed in the open field with three different objects. After 24 hours, the animal was replaced in the open field with two objects that were already known by the animal and a new object. In the second procedure the animals were placed in the open field with two objects located in the adjacent corners of the open field. After 24 hours the animal returned to the open field with an object in the same position and the other object in the diagonal corner of the open field. In the third procedure the animal was placed in a context A with two identical objects. After five minutes the animal was placed in a context B with two identical objects, but different when compared to the objects presented in the context A. During the test phase, the animal was placed in one of the two contexts with one object from the context A and another object from the context B. It was calculated the recognition index: RI = (time spent in the new object/time spent in the object already known + time spent in the new object) X 100. The data were submitted to a Student s t test for independent samples (p<0.05). The results showed that malnourished animals presented lower recognition indexes as compared with control animals in all the experiments, suggesting that early protein malnutrition impairs memory in procedures of object recognition. Key-words: malnutrition, learning, recognition memory.