Imunodetecção do receptor metabotrópico mGluR8 no núcleo arqueado do hipotálamo de ratos Wistar e estudo dos efeitos, no receptor, resultantes da exposição oral sub-crônica ao glutamato monossódico / Imunodetecction of mGluR8 receptor in the arcuate nucleus of the hypothalamus of Wistar rats and study of the effects, on the receptor, resulting from sub-chronic exposure to monosodium glutamate

Thaís Fernanda Pinto de Almeida Freitas

Food is part of human culture not only associated to physiological needs. Food is composed of several molecules among them amino acids. Glutamate (GLU) is the anion of one of the main amino acids found in foods that, besides being part of the food composition, is a molecule essential for human physiology. It can also be ingested due to the use of the food additive monosodium glutamate (MSG). The GLU performs many functions in the body, among them we could mention: excitatory neurotransmitter in the central nervous system, precursor of GABA and other amino acids such as proline and glutamine. As a neurotransmitter GLU acts on four types of receptors: ionotropic (AMPA, NMDA and kainate) and metabotropic (mGluR1-mGluR8) divided into three groups according to their genetic homology. These receptors are present in nearly all central nervous system (CNS) and other organs such as heart, lung and intestine. MSG is used as a flavor enhancer all over the world. The discovery of the basic taste due to glutamate, led to the industrial production of its salt, monosodium glutamate. The basic taste induced by glutamate is called Umami, which translated from Japanese, means good taste, delicious. There are numerous studies on the use of MSG as a food additive (technological function), as well as its physiological functions and its effects in the organism. International organizations and regulatory agencies of many countries have reported and / or evaluated that the use of MSG as a food additive is safe. However, some authors have reported adverse effects associated with exposure to MSG. Thus, this study aimed to assess the presences of the metabotropic receptor mGluR8 in the arcuate nucleus of the hypothalamus (ARH) of Wistar rats, and to evaluate the effects in the mGluR8 receptor resulting from the dietary intake of different concentrations of MSG (0% [control], 1%, 2 , 5% and 5%) during 90 days. Also, it was evaluated the body weight gain of the rats fed with the diets containing MSG in the different concentrations. To demonstrate the presence of the mGluR8 receptor immunohistochemistry technique was employed, and in order to elucidate the weight gain, the animals were weighed weekly. All the data, cell counts from the immunohistochemistry technique and from the rats weighing, were evaluated by analysis of variance. The results showed no significant difference (p<0.05) for both: body weight gain and the presence of mGluR8 receptors among the animals that were fed with the diets containing the different MSG levels

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