Loss of adaptability of horizontal optokinetic response eye movements in mGluR1 knockout mice.

Metabotropic glutamate receptor subtype 1 (mGluR1) plays an essential role in the cerebellar long-term depression (LTD). We examined the dynamic characteristics and adaptability of horizontal vestibulo-ocular reflex (HVOR) and optokinetic response (HOKR) eye movements in mGluR1 knockout mice. A mild difference was seen in the HOKR/HVOR dynamics between the wild-type and mGluR1(-/-) mice. Exposure to 1 h of sustained screen oscillation, which induced HOKR adaptation in wild-type mice, induced no change in mutant mice. These results suggest that the mGluR1 plays an essential role in the adaptation of HOKR, and LTD underlies the adaptation of ocular reflexes.