Motor learning in common marmosets: Vestibulo-ocular reflex adaptation and its sensitivity to inhibitors of Purkinje cell long-term depression

- We developed an eye movement measuring system for marmosets.
- We developed a protocol of adaptation of vestibulo-ocular reflex for marmosets.
- T-588, a blocker of cerebellar LTD, blocks vestibulo-ocular reflex adaptation.
- Nimesulide, a blocker of LTD, also blocks vestibulo-ocular reflex adaptation.
- The present results suggest that LTD underlie cerebellar motor learning.

Adaptation of the horizontal vestibulo-ocular reflex (HVOR) provides an experimental model for cerebellum-dependent motor learning. We developed an eye movement measuring system and a paradigm for induction of HVOR adaptation for the common marmoset. The HVOR gain in dark measured by 10° (peak-to-peak amplitude) and 0.11-0.5 Hz turntable oscillation was around unity. The gain-up and gain-down HVOR adaptation was induced by 1 h of sustained out-of-phase and in-phase 10°-0.33 Hz combined turntable-screen oscillation in the light, respectively. To examine the role of long-term depression (LTD) of parallel fiber-Purkinje cell synapses, we intraperitonially applied T-588 or nimesulide, which block the induction of LTD in vitro or in vivo preparations, 1 h before the test of HVOR adaptation. T-588 (3 and 5 mg/kg body weight) did not affect nonadapted HVOR gains, and impaired both gain-up and gain-down HVOR adaptation. Nimesulide (3 and 6 mg/kg) did not affect nonadapted HVOR gains, and impaired gain-up HVOR adaptation dose-dependently; however, it very little affected gain-down HVOR adaptation. These findings are consistent with the results of our study of nimesulide on the adaptation of horizontal optokinetic response in mice (Le et al., 2010), and support the view that LTD underlies HVOR adaptation.