Rod- and cone-associated interphotoreceptor matrix in the rat retina. Differences in light-evoked distributional changes.

Several of the components of the interphotoreceptor matrix (IPM) in the rat have recently been shown to undergo a light-evoked shift in distribution or molecular conformation. In the light, the IPM appears concentrated at the apical surface of the retinal pigment epithelium (RPE) and in the basal outer segment region at the inner and outer segment junction, with relatively little present in the intervening interstitial zone adjacent to the outer segments. By contrast, the IPM in the dark is distributed almost uniformly across the outer segment layer. In the present study, the authors explored whether specialized domains of IPM known as the cone matrix sheaths undergo light-induced changes similar to those previously shown for the IPM as a whole. Fluorescence lectin histochemistry was used on retinal sections of light- and dark-adapted rats with lectins that show selective or preferential binding to cone matrix sheaths, peanut agglutinin (PNA), and Ricinus communis agglutinin (RCA-1). Lectin binding to cone matrix sheaths was the same in both lighting conditions, unlike the rod-associated IPM. These experiments and others using pretreatment of sections with neuraminidase suggested different roles of RCA-1 and PNA-binding components of the IPM in different photoreceptor-RPE cell interactions, including the transfer of substances between the two cell types and retinal adhesion.