Why Do Corticosteroids Increase the ERG Amplitude? an Experimental Study in Rabbits
Effects of betamethasone and dexamethasone (which have no mineralocorticoid action) on the visual function of adult albino rabbits were studied in in vitro and in vivo. In in vitro study, betamethasone and dexamethasone had no effects on ERG at a concentration of 4x 10-5 g/ml or below. Concentration of 8x 10-5 g/ml increases the amplitudes of in vitro ERGs, but the concentration was considered too high to be a possible level in vivo. An intravenous injection (single shot) of betamethasone 0.5 mg/kg body weight did not change ERGs and VECPs within 5 hours observations. In chronic in vivo study (daily intravenous injections of betamethasone 0.1 mg/kg and 0.3 mg/kg body weight for 15 days), ERGs did not change so much.
Based on these observations, we concluded that glucocorticoids have no direct effect on the visual functions of rabbits, and that the increase of ERG amplitude previously reported might be secondary to any environmental change.
KeywordsVisual Function Single Shot Implicit Time Mammalian Retina Cotton Wick
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