Effects of blocking the hyperpolarization-activated current (I-h) on the cat electroretinogram

The temporal properties of the electroretinogram (ERG) recorded from cat ey es were analyzed in the presence of either Cs+ or zatebradine which are kno wn to inhibit the hyperpolarization activated current (I-h) in retinal rods . Both Cs+ and zatebradine reduce the ERG response to high-frequency sinuso idal stimuli of high mean luminance and contrast. Conversely, blockade of I , has no effect on the frequency response characteristics of the isolated r eceptor component (PIII). These observations support the idea that I-h play s an important role in the transfer of signals from photoreceptors to secon d order neurons by suppressing the slow components originated in the photot ransductive cascade. The result of this operation is an enhancement of the light response in a range of temporal frequencies relevant to vision. (C) 1 999 Elsevier Science Ltd. All rights reserved.