Tolerance of horizontal cells to excitotoxicity in the developing FVB/N mouse retina.

We investigated the effect of L-glutamate on horizontal cell growth after postnatal photoreceptor degeneration in the developing FVB/N mouse retina, using immunocytochemistry with antisera against calbindin D-28 K (calbindin) or neurofilament 200 NEI4. The numbers of horizontal cells and amount of axonal arborization in the outer plexiform layer were unchanged in FVB/N mice injected with L-glutamate. Instead, more numerous processes emerging from horizontal cells descended into the inner plexiform layer (IPL) and formed a loose network in stratum I. Our results clearly demonstrate that horizontal cells are resistant to excitotoxicity by excessive glutamate, and that sprouting of horizontal cell axons into the IPL is potentiated by excessive glutamate in FVB/N mice as they mature.