Development of light-evoked changes of the interphotoreceptor matrix in normal and RCS rats with inherited retinal...

The interphotoreceptor matrix (IPM) has recently been shown to undergo a change in distribution following the transition between light and dark [IPM light response: Uehara et al., (1990 b) Science 248, 1633-36]. In the present study, the development of light-evoked IPM changes has been examined histochemically in the retinas of normal and Royal College of Surgeons (RCS) rats with inherited retinal dystrophy between the ages of post-natal day (P) 12 and 40. In normal rats at P12 and P14, the IPM was uniformly and intensely stained with the colloidal iron reaction in both light- and dark-adapted retinas. The capacity of the IPM to undergo the light-evoked distributional change shown previously in adults appeared between P14 and P16. At P16 and older ages, the IPM in light-adapted rats was concentrated in bands at the apical and basal regions of the outer segment zone, whereas the IPM remained uniformly stained in dark-adapted rats. In RCS rats, the light-evoked change developed at the same age as in normal rats, although it was lost between P20 and P25. Correlations of the time of onset and loss (in RCS rats only) of the light-evoked IPM distributional change with other developmental events suggest that mature, organized photoreceptor outer segments are necessary for the IPM light response to occur, and that in RCS rats the disruption of the IPM light response may contribute to the characteristic accumulation of IPM in the basal outer segment zone and photoreceptor cell death in this form of retinal degeneration.