We investigated the effects of early environmental stimulation on spreading depression in the cerebral cortex of male Wistar adult (90 day old) well-nourished (23% protein diet) and early malnourished (8% protein) rats. Environmental stimulation was performed during the suckling period or after weaning. Control rats were housed in a standard environment. Environmental stimulation after weaning produced a reduction of body weights in well-nourished rats, and an increase in wet, but not dry brain weights, in malnourished rats. Environmental stimulation during suckling was associated with reduced spreading depression velocities in the malnourished, but not in the well-nourished group. In well-nourished rats stimulated during suckling, spreading depression velocities in the occipital and parietal regions of the same hemisphere were significantly different, the occipital area presenting lower values than the parietal region. The results indicate that environmental conditions prevailing during brain development can alter electrophysiological parameters of spreading depression of adult rats, the suckling period being more susceptible to such environmental conditions and the occipital cortex being more affected than the parietal region. Data also suggest that the nutritional status can influence brain spreading depression responses to environmental stimulation, malnourished rats being more effected than the well-nourished ones.
Tissue distribution of nitric oxide-synthases was investigated in the rat hippocampus and visual cortex under nutritional changes induced by modification of the litter size. Young (30-45-days-old) rats, suckled in litters formed by 3,6 or 12 pups (called small, medium and large litters, respectively), were studied by using nicotine-adenine-dinucleotide phosphate-diaphorase histochemistry (shortly, diaphorase), a simple and robust procedure to characterize tissue distribution of nitric oxide-synthases. We assessed morphometric features of the diaphorase-positive cells in visual cortex, and the neuropil histochemical activity in hippocampal CA1 and dentate gyrus using densitometry analysis. In the large-litter group, the labeled-cell density in white matter of area 17 was higher, as compared to the small-litter group. There was a clear trend, in the large-litter group, to lower values of soma area, dendritic field and branches per neuron, but the differences were not significant. Densitometry analysis of hippocampus revealed a significant increase in the relative neuropil histochemical activity of the dentate gyrus molecular layer in the larger litters, which may be associated to increased compensatory blood flow in the hippocampus. The pathophysiological mechanisms of the observed changes remain to be investigated.
RESUMO: É feita uma revisão sobre as estratégias e efeitos da estimulação sensorial e ambiental de indivíduos desnutridos. Reportam os autores evidências provenientes de experimentos com modelos animais e de estudos em seres humanos, mostrando os benefícios da administração da estimulação sensorial ou psicossocial programadas sobre as funções neuro-comportamentais. Mostram ainda a importante participação que a plasticidade cerebral pode ter neste processo. Finalmente enfatizam que as evidências eletrofisiológicas - obtidas pela técnica da depressão alastrante cortial em animais - e as observações em seres humanos indicam que as regiões cerebrais comportam-se diferencialmente nesta recuperação. Daí, sugerem uma abordagem nos cuidados médicos em indivíduos desnutridos levando em conta estas peculiaridades regionais do cérebro.
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