Corneal endothelium plays an essential role in the maintenance of corneal transparency. For the purpose of developing a new experimental animal model for corneal endothelial research, we examined the morphological features of the ferret corneal endothelium and evaluated the potential of this animal as an experimental model for corneal endothelial research. Histological examination of ferret corneas was performed and compared with that of rabbit and cynomolgus monkey corneas. Through the use of flat-mount immunohistochemical analyses, our findings showed that function-related markers of corneal endothelium, such as ZO-1, N-cadherin and Na⁺/K⁺-ATPase, exist in ferret corneas. Clinically important corneal endothelial parameters, such as corneal endothelial cell density, rate of hexagonal cells, and coefficient of variation, were also examined in the ferret corneal endothelium by using the clinical analysis software normally used for human subjects. We obtained a successful primary culture of ferret corneal endothelial cells composed of a continuous monolayer of hexagonal shaped cells, maybe to the in vivo corneal endothelium. Moreover, and also similar to the in vivo corneal endothelium, the expressions of ZO-1 and Na⁺/K⁺-ATPase were maintained in the cultivated ferret corneal endothelial cells. Our results suggest that ferrets are a useful experimental animal model and may provide a new insight to fill the gap between rabbit and monkey animal research models for researchers in the field of ophthalmology.

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The purpose of this study was to examine whether the drug-induced alteration of electroretinogram (ERG) corresponding to that reported in humans could be detected by ERG assessment of the function of rod- and cone-pathways in cynomolgus monkeys.
Digoxin, which has been reported to cause visual disturbances and reversible attenuation of the cone-driven ERGs in humans, was administered daily to five cynomolgus monkeys by intramuscular injection at a dose of 0.01 mg/kg/day for one month, followed by a one-month recovery period. According to a standardized procedure in humans, the rod-driven ERG (rod response), rod- and cone-driven ERG (combined rod-cone response) and cone-driven ERGs (single-flash cone response and 30 Hz flicker) were recorded serially.
Increased implicit times of the combined rod-cone response and the single-flash cone response, and decreased amplitudes of the single-flash cone response and the 30 Hz flicker were detected. All changes in ERG recovered during the recovery period. No apparent attenuation was observed in the rod response.
In conclusion, a digoxin-induced reversible attenuation of the cone-driven ERGs could be detected by the ERG assessment of the function of rod- and cone-pathways in cynomolgus monkeys. Our results imply that this method may be useful for collecting non-clinical data that is relevant to humans.

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