NutriÃÃo, hipertiroidismo precoce e desenvolvimento cerebral: estudo em ratos recÃm-desmamados

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

It is known that early alterations of thyroid function interferes with cerebral development and physiology. In this work we investigated the effects of early treatment with thyroxin (T4) on the propagation of cortical spreading depression (SD) in weaned rats. Female adult Wistar rats fed a lab chow diet (CD; 23% protein) were treated with T4 (20ug/kg/day, single ip injection) during either gestation (group CDH-G) or during the first or third week of the lactation period (groups CDH-L1 and CDH-L3 respectively). They were compared with 3 control groups, injected at the same periods with saline solution (groups S-G, S-L1 and S-L3, respectively). One additional malnourished group was treated with T4 at L3, and another one was studied at the ânaÃveâ condition (i.e., without receiving any injection or other kind of manipulation). Body weight and some dimensions (longitudinal body axis, as well as laterolateral and antero-posterior skull axis) were obtained at days 2, 5, 10, 15, 20 and 25. From weaning (day 25) to day 35, the pups were submitted to the electrocorticogram- and slow potential change recordings of SD, which was elicited by KCl at the frontal cortex and recorded at 2 points of the parietal region. T4-treated rats presented reduction in body and brain weights. Compared to the controls, serum T3 levels were found to be reduced in the group treated during gestation and increased in those treated during lactation. Serum T4 levels changed in the opposite direction. The malnourished group presented lower body and brain weights, when compared to the well-nourished control. T4 treatment associated with malnutrition resulted in high mean SD-velocities, but the differences from the control were not significant. In the groups CDH-G and CDH-L3 Impairment in body growth was not uniform, so that we found variable degrees of impairment between body- and skull growth parameters. The results indicate that T4 treatment early in life can alter developmental, hormonal and electrophysiological parameters, the magnitude of these changes being dependent on the period in which the T4-treatment was performed, as well as on the nutritional status of the animals. The data: 1)reveals that T4-treatment renders the cerebral cortex more susceptible to SD, as judged by their increased velocities of propagation; 2) indicate that the association of T4 and malnutrition does not annihilate, nor potentiate, their effects on SD; 3) suggest more awareness to the relevance of the early treatment of hyperthyroidism in children, to prevent damage to the nervous system

ASSUNTO(S)

hipertiteoidismo nutrition depressao alastrante nutricao nutricao spreading depression hyperthyroidism

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