Gabbott, P. L. and Stewart, M. G.
Visual deprivation alters dendritic bundle architecture in layer 4 of rat visual cortex.
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The effect of visual deprivation followed by light exposure on the tangential organisation of dendritic bundles passing through layer 4 of the rat visual cortex was studied quantitatively in the light-microscope. Four groups of animals were investigated: i) rats reared in an environment illuminated normally – Group 52dL; ii) rats reared in the dark until 21 days post natum (DPN) and subsequently light exposed for 31 days – Group 21/31; iii) rats dark-reared until 52 DPN and then subsequently light exposed for 3 days – Group 3dL; and iv) rats totally dark-reared until 52 DPN – Group 52DPN. Each group contained 5 animals. Semithin 0.5-1µm thick resin embedded sections were collected from tangential sampling levels through the middle of layer 4 in area 17 and stained with toluidine blue. These sections were used to quantitatively analyse the composition and distribution of dendritic clusters in the tangential plane. The key result of this study indicates a significant reduction in the mean number of medium- and small-sized dendritic profiles (diam. < 2µm) contributing to clusters in layer 4 of groups 3DL and 52dD compared with group 21/31. No differences were detected in the mean number of large-sized dendritic profiles composing a bundle in these experimental groups. Moreover the mean number of clusters and their tangential distribution in layer 4 did not vary significantly between all four groups. Finally, the clustering parameters were not significantly different between groups 21/31 and the normally reared group 52dL.
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