Abstract
Newborn albino rats show the same loss of inner retinal layers and of b-wave on treatment with sodium TL-glutamate as do mice. Values for four enzymes metabolizing glutamate or glutamine have been determined on normal and glutamate-treated rats. The retinas of normal rats contain almost twice as much glutaminase I per unit weight as those of glutamate-treated animals. There is no measurable "glutaminase II" activity in rat retina. There is no difference between retinas of normal and treated animals in content of glutamosynthetase and glutamotransferase. These findings are consonant with our hypothesis that glutamate action on the retina of the newborn rat is by repression of synthesis of an enzyme whose reaction product is glutamate itself. They do not eliminate the possibility that direct competitive inhibition by glutamate may play a role.