Does light stimulus at eye opening of the developing rat influence retinal expression of GTP-binding protein (G(0))?

We previously hypothesized that light stimulus at eye opening of rats on postnatal days (P) 13 or 14 has an effect on the expression of GTP-binding proteins (G(0) in the retina) because the concentration of G(0) alpha increased rapidly between P10 and P15. This hypothesis was also supported by the findings that the distribution of G(0) alpha in the retina was almost the same as that of adult rats between P10 and P15. In this study, pregnant rats were kept in a dark room after vaginal plugs were identified; they gave birth to their pups in the dark, and their pups were reared by their mothers in the dark. The postnatal rats were sacrificed at P10, P15, P18, P22, P24, P27, and P30. Their retinas were investigated immunochemically and immunohistochemically, using G(0) alpha antibody, and these results were compared with those of the rat pups reared normally. Only G(0) alpha immunoreactivity in the inner nuclear layer of rats reared in the dark room was weaker than in the controls; the distribution of G(0) alpha in the retina did not change, as compared with pups reared in normal conditions. In addition, in pups reared in the dark, G(0) alpha increased rapidly from P10 to P15. However, the concentration of G(0) alpha in the retina of rat pups reared in the dark was significantly low at P22 (p < 0.01) and P30 (p < 0.05), as compared with pups reared in normal conditions. Although the function of G(0) in the retina may have something to do with the light stimulus after eye opening, it appeared that the expression of G(0) was not influenced by light stimulus at eye opening.