Retarded vestibular compensation in mutant mice deficient in delta 2 glutamate receptor subunit.

The delta 2 subunit of ionotropic glutamate receptors is expressed only in the cerebellar Purkinje cell. In mutant mice deficient in the delta 2 protein, cerebellar long-term depression and motor coordination are impaired. We examined behavioural plasticity in these mutant mice after unilateral vestibular destruction. After intratympanic injection of sodium arsanilate, the mice showed roll head tilt and their righting response under a rotation load was impaired. These symptoms improved with time. However, compensation of the righting response was retarded in the mutant mice. These results suggest that motor learning of the delta 2 mutant mice is disturbed, and that the static and dynamic components of vestibular compensation may be controlled by different neuronal mechanisms.