Immunohistochemical localization of amino acids in the diabetic retina of Goto-Kakizaki rats.

The Goto-Kakizaki (GK) rat is a spontaneous model of non-insulin-dependent diabetes mellitus without obesity and diabetic retinopathy. We examined the retinal distribution of L-glutamate, gamma aminobutyric acid (GABA), glycine, and L-aspartate as neurotransmitters in the GK rat retina, using an immunohistochemical method with high-affinity antibodies. The retinal structures in the GK rats were the same as the controls. However, in the GK rats, immunoreactivity of L-glutamate and GABA was observed in the Müller and photoreceptor cells in addition to the immunoreactivity in normal rats. There was no change in glycine distribution between GK rats and controls. In the GK rats, L-aspartate accumulated in the inner segment of the photoreceptor cells in addition to the normal distribution. We consider that these immunoreactivity patterns in the GK rat retina might be induced by ischemia associated with diabetes mellitus.