| Abstract No.: | C-D3129 |
| Country: | Canada |
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| Title: | DISTRIBUTION OF CALCIUM-BINDING PROTEINS IN VISUAL AND AUDITORY CORTICES FOLLOWING NEONATAL ALTERATIONS OF THE VISUAL SYSTEM IN HAMSTERS |
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| Authors/Affiliations: | 1 Sébastien Desgent*; 2 Denis Boire; 1 Maurice Ptito;
1 Université de Montréal, QC, Canada; 2 Université du Québec à Trois-Rivières, QC, Canada
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| Content: | Objectives: In the normal hamster, different calcium binding proteins (CaBPs) chemoarchitectonic features exists between primary visual and auditory cortices (Desgent et al., 2005). In addition recent evidence suggests that the expression of CaBPs is dependant upon afferent activity. Whether, the specific pattern of expression of CaBPs in sensory cortices is dependant upon input activity of a specific sensory modality in presently unknown. Inter-modal cortical activations following sensory deprivations have been demonstrated in animal models as well as in humans. Namely visual cortical activations were reported in congenitally blind subjects as well as experimentally enucleated animals or in animal models of cross-modal rewiring. In the present study, we tested the hypothesis that the expression of the CaBPs: parvalbumin (PV), calretinin (CR) and calbindin (CB) is dependant upon sensory experience. We investigated the effect of permanent afferent deprivation on CaBPs neurons in primary and associative visual cortices (V1, V2M, V2L) and the primary auditory cortex (A1) of adult hamsters.
Material & Methods: Golden syrian hamsters underwent lesions of the stratum opticum of the superior colliculus, enhancing the visual activation of secondary visual pathways through the lateral posterior nucleus (LP), or binocular enucleation at birth inducing auditory activation of deprived visual cortex, Immunohistochemical analysis using antibodies against each of the CaBPs was performed on the sensory cortices at p120. Changes in cortical CaBPs expressions were evaluated with computer-based stereological quantitative techniques.
Results: In normal controls, PVir cells were mostly located in layer II-III and V for V1, V2M, V2L and in layers III-IV for A1. Collicular lesions or enucleation did not affect the total number of neurons and volume, but induced significant changes in the laminar distributions of PVir and CBir cells. Collicular lesions induced a significant but lesser reduction in the number of PVir neurons in V1 layer V than enucleation. In enucleated hamsters, there was a significant increase in layer IV and reduction in layer V of PVir cell bodies. This altered distribution of PVir neurons in V1 resembled that of the primary auditory cortex. CBir neurons were mostly distributed in layers II/III and in layer V of both auditory and visual cortices, but were more numerous in layer V of V1 in controls than in both visual deprivation models. CRir interneurons were similarly distributed in both cortices with a peak in superficial layers II/III. Our results show that only two subpopulations of CaBPs cortical interneurons (PV and CB) are sensitive to alterations of visual inputs.
Conclusions: Certain features of the laminar distribution of the expression of CaBPs are dependant upon sensory activity. We demonstrate that the expression pattern of parvalbumin in the deprived visual cortex can become similar to that of the intact auditory cortex and suggest that the expression of some CaBPs is also modulated by sensory modality specific activity.
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