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| Author(s): |
Graziela Ligia da Silva Santos
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Marília. 2019-05-31. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Filosofia e Ciências. Marília |
| Defense date: | 2019-05-06 |
| Advisor: | Ana Claudia Figueiredo Frizzo |
| Abstract | |
During aging, in mammals, it is common the development of presbycusis, characterized by loss of cells in the cochlea associated with changes in the neuronal functions of the nuclei of the central auditory system (SAC) that cause auditory impairment. Among the common neuronal changes in aging are changes in the neuronal expression calcium-binding proteins (CaBPs), which are essential for processing in the auditory pathway stations, which can thus constitute the mechanism of presbycusis. Among the possible forms of treatment and/ or prevention of presbyacusis is the supplementation with antioxidant and/ or neuroprotective substances that may delay the neuronal loss and/ or functional alterations of the neurons. Among these, the hormone melatonin, has demonstrated important antioxidant and otoprotective action that can occur independent or dependent on the melatonin receptor MT1 and MT2. However, it is unclear whether SAC stations express suche receptors and whether such expression could vary in aging. Considerering that the CaBPs are altered in the elderly, it is proposed to verify if these altererations occur with possible alterations in the expression of the melatonin receptors in aging. Such information will contribute to understanding the mechanisms involved in presbycusis and to investigating possible otoprotective therapies in aging. Objective: To evaluate the expression of CaBPs and melatonin MT1 and MT2 receptors in synaptic stations neurons that compose SAC in young and elderly rats. To compare the morphology of immunoreactive neurons to CaBPs between young and elderly rats. Methods: Enceplhalic cords from young and elderly rats were processed using immunohistochemistry technique to indentify the proteins of parvalbumin (PV), calbindin (CB), calretinin (CR) and the MT1 and MT2 receptors. Quantification of the number of CaBPs positive cells will be performed by stereology and receptor expression will be assessed by optical density. Results: The density of PV immunoreactive cells (PV-ir) was lower and the PV-IR neuron volume in the inferior colliculus was higher in the elderly group. The number of CB-IR and CR-IR cells in the superior olivary complex was also lower in the elderly group when compared to the young group. In the cochlear nucleus, the numbers of CR-IR cells was lower in the elderly group when compared to the young group. In the medial geniculate body there was no difference in cell density and aa decrease in the volume of CB-IR neurons was observed in the elderly group. There was an increase in MT1 expression in the cochlear nucleus, superior olivary complex and inferior colliculus of elderly rats. The presence of MT1 was verified in the medial geniculate body only in the elderly group. The presence of the MT2 receptor was observed in the cochlear nucleus region, superior olivary complex, inferior colliculus and medial geniculate body only in the elderly group. Discussion: The lower expression of CaBPs and the morphological alteration in CB-IR and PV-IR neurons in central auditory pathways in elderly rats indicates that these nuclei undergo aging. Already the increase in MT1 receptor expression and the presence of the MT2 receptor with aging suggests that this molecule has an important neuroprotective action in the nuclei of the auditory pathway. Conclusion: The CaBPs presented lower expression in the nuclei of the SAC in the elderly group. The MT1 and MT2 melatonin receptors presented greater expression in the SAC nuclei in the elderly group. The older group presented an even higher volume of the PV-IR neurons of the inferior colliculus and lower volume of the CB-IR in the medial geniculate body. (AU) | |
| FAPESP's process: | 17/09484-1 - Expression of neuroactive substances in auditory pathway encephalic centers in aging |
| Grantee: | Graziela Ligia da Silva Santos |
| Support Opportunities: | Scholarships in Brazil - Master |