O envelhecimento do complexo geniculado lateral de ratos: mudanças morfológicas e ritmicidade diária de calretinina
Normal aging is accompanied by declines in visual system even in the absence of pathological processes. Among the components of this system, the lateral geniculate nucleus (LGN) comprises the dorsal lateral geniculate nucleus (dLGN), intergeniculate leaflet (IGL) and ventral lateral geniculate nu...
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| Formato: | doctoralThesis |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/26405 |
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| Resumo: | Normal aging is accompanied by declines in visual system even in the absence of
pathological processes. Among the components of this system, the lateral geniculate nucleus
(LGN) comprises the dorsal lateral geniculate nucleus (dLGN), intergeniculate leaflet (IGL)
and ventral lateral geniculate nucleus (vLGN). A characteristic of these nuclei is the
immunoreactivity of calcium binding proteins (CaBPs), which regulates the intracellular
concentration of this ion and presents a daily and regional expression. In parallel, modern
theories of aging correlates functional deficits of neurons to dysregulation of calcium
homeostatic mechanisms. In this context, the present study aims to describe quantitative
morphological parameters of LGN and immunoreactivity of the CaBP calretinin (CR) in
distinct phases of day across different age groups. Male wistar rats were divided into three
age groups: young, middle-age and aged (3, 13 and 23 months old) and perfused with
formalin (10%) in Zeitgeber times (ZTs) corresponding to distinct photic conditions, namely
ZT 0 (dark/light transition), ZT 6 (light), ZT 12 (light/dark transition), ZT 14( beginning of dark)
and ZT 18 (dark) . Then, the brains were sectioned and submitted to immunohistochemistry
for Neuronal Nuclei protein (NeuN) with Nissl counterstain or immunohistochemistry for CR.
Through the stereological methodologies of optical fractionator and Cavalieri estimator we
estimated the regional volume, neuronal and glial number, glia/neuron ratio and CR+
neuronal number in the CGL nuclei. We observed LGN neuronal numbers remained stable
during aging. However, glial numbers, glia/neuron ratio and volume increased in a regionspecific manner. In addition, we observed a peak of CR-immunoreactive cells in the light
phase that was diminished in the beginning of the dark in all LGN subnuclei of young
animals. Furthermore, we show an age-related reduction of CR+ cells in all subnuclei at ZT
12, as well as in ZT 6 of IGL and the external portion of vLGN. These reductions seem to be
due to the neuron capacity in express CR rather than neuronal loss, since no alterations
were observed in total cell numbers. The daily rhythm of CR observed in young is lost in
middle-aged and aged animals and were detected only in the light phase. |
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