The bidirectionality of motor learning in the vestibulo-ocular reflex is a function of cerebellar mGluR1 receptors

J Neurophysiol. 2010 Dec;104(6):3657-66. doi: 10.1152/jn.00664.2010. Epub 2010 Oct 6.

Abstract

Bidirectional changes in synaptic transmission have the potential to optimize the control of movement. However, it can be difficult to establish a causal relationship between the bidirectionality of synaptic plasticity and bidirectional changes in the speed of actual movements. We asked whether metabotropic glutamate receptor 1 (mGluR1) receptors, which participate in cerebellar long-term depression (LTD), are necessary for bidirectional motor learning in the vestibulo-ocular reflex (VOR). Cerebellar LTD and long-term potentiation (LTP) are thought to cause increases and decreases, respectively, in the gain of the VOR; the direction of learning depends on the behavioral protocol. We injected either the mGluR1 agonist (S)-DHPG or the antagonist YM 298198 bilaterally into the flocculus of alert cats, and then induced motor learning. In the presence of YM 298198, the VOR gain decreased in gain-up, as well as in gain-down protocols. (S)-DHPG augmented gain-up learning. Gain-down learning was not significantly affected by either drug. These results supported the hypothesis that gain-up learning relies on cerebellar LTD, but gain-down learning relies on a different mechanism. In the absence of mGluR1 activity, cerebellar LTD may be replaced with LTP, permitting learning in only one direction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzimidazoles / pharmacology
  • Cats
  • Cerebellar Cortex / drug effects
  • Cerebellar Cortex / physiology*
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Eye Movements / physiology*
  • Learning / drug effects
  • Learning / physiology*
  • Long-Term Potentiation / drug effects
  • Long-Term Potentiation / physiology*
  • Long-Term Synaptic Depression / drug effects
  • Long-Term Synaptic Depression / physiology*
  • Methoxyhydroxyphenylglycol / analogs & derivatives
  • Methoxyhydroxyphenylglycol / pharmacology
  • Motor Activity / drug effects
  • Motor Activity / physiology*
  • Receptors, Metabotropic Glutamate / drug effects
  • Receptors, Metabotropic Glutamate / physiology*
  • Reflex, Vestibulo-Ocular / physiology*
  • Rotation
  • Synaptic Transmission
  • Thiazoles / pharmacology

Substances

  • 6-amino-N-cyclohexyl-N,3-dimethylthiazolo(3,2-a)benzimidazole-2-carboxamide
  • Benzimidazoles
  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • Receptors, Metabotropic Glutamate
  • Thiazoles
  • metabotropic glutamate receptor type 1
  • Methoxyhydroxyphenylglycol
  • 3,4-dihydroxyphenylglycol