Comparison of electroretinographic responses between two different age groups of adult dark agouti rats

Introduction: Experimental models for ophthalmic disease in rats are important in the study of mechanisms of disease as well in the development of novel treatment strategies. Maturation may cause a significant change in different retinal cell count and function. Thus in the interpretation of results from rat glaucoma models, an understanding of the effect of age on retinal histology and function is an important consideration. Purpose: To describe and compare the differences in electroretinographic responses between two different age groups of adult Dark Agouti (DA) rats. Methodology: The electroretinographic responses of two different age groups of adult DA rats were compared. Animals were divided into younger adult DA rats 10-12 weeks (n=8) and older adult DA rats 17-19 weeks (n=8). Full field electroretinography (ERG) was recorded simultaneously from both eyes after dark adaption and light adaption and parameters including the positive scotopic threshold response (pSTR), negative scotopic threshold response (nSTR), scotopic a-wave, b-wave, photopic a-wave, b-wave and photopic negative response (PhNR) were compared between groups. Results: The older adult rats displayed lower stimulation thresholds of the STRs (pSTR and nSTR) and higher amplitudes of pSTR, scotopic a-wave and b-wave, photopic b-wave and PhNR amplitudes, with shorter implicit times. Photopic a-wave amplitudes were however higher in the younger adult rats. Conclusion: In summary, for the rod system, photoreceptor, bipolar cell and RGC activity was enhanced in the older adult rats. For the cone system, RGC and bipolar cell activity was enhanced, while photoreceptor activity was depressed in the older adult rats. Such age-related selective modification of retinal cell function needs to be considered when conducting ophthalmic research in adult rats