To further assess the presence of glycogen in retinal
neurons of nondiabetic rats, eyes of additional 4-month-old
control male Sprague Dawley rats (n ¼ 6) were preserved in
Davidson’s fixative (DF), which provided superior retinal
morphology, glycogen preservation, and immunohistochemical
staining with several antigens, particularly GyP. Histochemical
staining for glycogen was performed with the periodic acid
Schiff (PAS) reaction with negative controls digested with
alpha amylase.