In vivo and in vitro development of the geniculocortical pathway in the mouse

• Main Author: Rennie, Suzanne
• Published: University of Edinburgh 1993
• Subjects: 571.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.661052

This is an investigation of the development of connections between the lateral geniculate nucleus (LGN) and the visual cortex in the mouse, using both <i>in vitro</i> and <i>in vivo</i> techniques. Visual cortical layer 4 is the target of ingrowing feniculate axons. Using immunohistological labelling techniques, I monitored the pre and postnatal migration of cells destined for layer 4 from the ventricular zone to the cortical plate <i>in vivo</i>. It was shown that, although the first of these cells enter the cortical plate as early as embryonic day 16 (E16), migration continues and layer 4 is not fully in place until postnatal day 7 (P7). The development of connections between the LGN and the visual cortex was investigated using <i>in vivo</i> immunohistological and tract-tracing methods with the carbocyanine dye, DiI. The LGN is formed between E12-14 and geniculocortical fibres are present in the visual cortex by E17. The main emphasis of this study was the mechanisms which control the outgrowth of axons from the LGN. Using an organotypic co-culture system, I searched for evidence of long range growth-promoting or trophic interactions between LGN explants and the occipital cortex. This technique has been widely used, with great success, by Yamamoto et al. (1989 and 1992), Bolz et al. (1990), Molnar and Blakemore (1991) and Toyama et al. (1991) to investigate the growth of axons into the visual cortex. Blocks of embryonic LGN were cultured in serum-free medium, either alone or with slices of embyonic cortex or early postnatal ocipital cortex, frontal cortex, cerebellum, medulla or liver (the ages of the explants were selected on the basis of the previous <i>in vivo</i> study).