Section 9
Chapter 8,451

Development and regulation of dendritic stratification in retinal ganglion cells by glutamate-mediated afferent activity

Bodnarenko, S.R.; Jeyarasasingam, G.; Chalupa, L.M.

Journal of Neuroscience: the Official Journal of the Society for Neuroscience 15(11): 7037-7045


ISSN/ISBN: 0270-6474
PMID: 7472459
DOI: 10.1523/jneurosci.15-11-07037.1995
Accession: 008450926

In the mature retina, the dendrites of retinal ganglion cells (RGCs) are segregated into either ON or OFF sublaminae of the inner plexiform layer (IPL), but early in development the dendritic processes of these cells are multistratified, ramifying throughout the IPL. We examined the time course of dendritic stratification in developing beta cells, the largest class of ganglion cells in the cat retina, by retrograde labeling of fixed tissue with Dil. Dendritic stratification begins in the central and peripheral retina by embryonic day 50, about 2 weeks before birth and is not fully completed until 5 months postnatally. A clear central-to-peripheral gradient in the incidence of stratified beta cells first becomes evident shortly after birth. This stratification process was effectively halted by short-term intraocular injections (4-11 d) of the glutamate analog 2-amino-4-phosphonobutyrate (APB), which hyperpolarizes rod bipolar cells and ON cone bipolar cells, thereby preventing the release of glutamate by these interneurons. APB treatment did not alter the somal sizes or the tangential extent of the dendrites of developing beta cells, nor did it cause abnormal loss of these neurons. The organization of the inner nuclear layer, containing the APB-sensitive bipolar cells, was also not compromised by such injections. When APB treatment was discontinued there was a rapid resumption of dendritic stratification resulting in a normal incidence of stratified RGCs. Thus, short-term APB treatment causes a delay rather than a permanent arrest of the stratification process. These results suggest that glutamate-mediated afferent activity regulates the restriction of developing RGC dendrites into ON and OFF sublaminae of the IPL and that such regulation takes place during a protracted developmental period.

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