Cell death in the mammalian visual system during normal development: II. Superior colliculus

Somatostatin-like immunoreactivity in the central visual pathway of the prenatal rat

Somatostatin (SRIF)-like immunoreactivity was localized in the central visual pathway of near-term prenatal rats using light-microscopic immunocytochemistry and a highly specific antibody to the peptide. SRIF was demonstrable in neuronal perikarya and fibers of the lateral geniculate nucleus, superior colliculus and visual cortex. At this stage the distribution of these elements had not attained the pattern seen in the adult. The presence of SRIF in the central visual pathway prior to maturation suggests a role for this peptide in the development of visual function.

Cell death in the mammalian visual system during normal development : I. Retinal ganglion cells

Degenerating cells may be observed with light microscopy in the hamster retinal ganglion cell layer during early postnatal development. On the first postnatal day, degenerating cell profiles were found at a rate of 2.7 per 1,000 live cells. This rate increased to a peak of 14.7 degenerating cells per 1,000 live on postnatal day 5 and then slowed to 4.2 per 1,000 live by postnatal day 10. These rates of cell death correspond to a 49% reduction in cell number in the ganglion cell layer. Examination of the spatial pattern of cell death revealed that although on visual inspection degenerating cells appear to occur in clumps, statistical analysis demonstrated a random distribution within renal areas. Across the retina, cell death rates were higher in peripheral retina than in central retina. The timing and pattern observed correspond well with that of cell degeneration observed in the superficial layers of the superior colliculus, the major target of the retinal projection.