Climbing fiber activity related to abnormal eye movements in GluRdelta2 knockout mice

Abstract

Ionotropic glutamate receptor δ2 subunit (GluRδ2) is specifically expressed in cerebellar Purkinje neurons (PNs). GluRδ2 knockout mice (δ2-/-) show the impairment in synaptic regulation and motor coordination. To elucidate how the GluRδ2 deficiency affects motor coordination, we have analyzed their eye movements and found that δ2-/- showed abnormal spontaneous and reflexive eye movements. In δ2-/-, eyes moved continuously with 1Hz and 10 Hz oscillatory components even if no stimulus was applied. δ2-/- showed a large phase delay in the optokinetic response and a high gain in the vestibulo-ocular reflex. Simultaneous recordings of the spontaneous eye movement and the activity of a floccullar PN revealed that PNs in δ2-/- tended to generate several forms of spike activities presumably induced by climbing fiber inputs. These activities showed the 10 Hz periodicity and correlated to the spontaneous eye movement. Abnormalities in spontaneous and reflexive eye movements were reduced by destruction of inferior olive nuclei by administration of 3-acetylpyridine. These results suggest that altered climbing fiber activities are related to abnormalities in the spontaneous and reflexive eye movements in GluRδ2 knockout mice. [Jpn J Physiol 54 Suppl:S179 (2004)]