Contribution of cerebellar intracortical inhibition to Purkinje cell response during vestibulo‐ocular reflex of alert rabbits.

Abstract

SUMMARY1. Ionophoretic application of bicuculline, an antagonist of y-aminobutyric acid (GABA), was used to examine the contribution of intracortical inhibition to vestibular responses of Purkinje cells in the cerebellar flocculus of alert rabbits.2. Purkinje cells were sampled extracellularly (with triple-barrelled micropipettes) from the floccular area where electrical stimulation through the micro-electrode evoked abduction of the ipsilateral eye, indicating its close functional relationship to the horizontal vestibulo-ocular reflex. These cells exhibited frequency modulation of simple spike discharges in-phase or out-phase with sinusoidal head rotation (0 5 cycles/s, 50 peak-to-peak) in the horizontal plane.3. Bicuculline was ejected ionophoretically through one barrel with a 20-60 nA current. The pharmacological effectiveness of the ejected bicuculline was confirmed for each Purkinje cell by its blocking action upon the depressant action of GABA applied ionophoretically through another barrel.4. Bicuculline usually shifted the simple spike modulation in the in-phase direction: it reduced the amplitude of out-phase modulation in three cells, converted out-phase modulation to the in-phase type in four cells, and increased in-phase modulation in five cells. In three other cells, however, bicuculline shifted the modulation in the out-phase direction.5. Because bicuculline application usually increased the resting discharge level of a Purkinje cell, ionophoretic application of DL-homocysteate was used in ten Purkinje cells to control for the effect of a generalized increase in excitability. In contrast to bicuculline, DL-homocysteate generally induced a slight increase of the simple spike modulation regardless of the phase relationship.6. Since frequency modulation of the simple spike discharges of flocculus Purkinje cells is presumed to contribute to the control of vestibulo-ocular reflexes, these results point to an important functional role of intracortical post-synaptic inhibition in the cerebellar cortex.

Dendritic Calcium Signaling Triggered by Spontaneous and Sensory-Evoked Climbing Fiber Input to Cerebellar Purkinje Cells In Vivo

“…8). Application of these blockers increased SS frequency from 34.3 Ϯ 10.5 Hz to 61.7 Ϯ 15.8 Hz (n ϭ 3 cells, p ϭ 0.036) as expected from block of tonic, ongoing GABAergic inhibition to Purkinje cells (Miyashita and Nagao, 1984;Jaeger and Bower, 1994;Häusser and Clark, 1997). The branch-to-branch variability of the peak amplitude of [Ca 2ϩ ] transients was reduced by blocking inhibitory inputs (Fig.…”

Mechanisms underlying vestibulo‐cerebellar motor learning in mice depend on movement direction

“…). For example, these include those engaging the molecular layer interneurons, which directly control the rate and regularity of SS activity (Miyashita & Nagao, ; Gao et al . ).…”

“…). The inhibitory interneurons, as well as the plasticity mechanisms that control their activity, are probably also relevant for the inversion of the vestibular signal that occurs between the vestibular organs and the Purkinje cells (Miyashita & Nagao, ). Contraversive head rotation decreases activity in the vestibular ganglion neurons but correlates with an increased firing rate in Purkinje cells (Fig.…”

Target-Dependent Feedforward Inhibition Mediated by Short-Term Synaptic Plasticity in the Cerebellum

“…This results in feedforward inhibition (FFI), which can rapidly terminate the membrane depolarization of PCs induced by PF inputs (Eccles et al, 1967;Brunel et al, 2004;Mittmann et al, 2005). FFI has an important role in the cerebellar function in vivo (Miyashita and Nagao, 1984;Eccles et al, 1966d;Wulff et al, 2009), but it is not known how inhibitory neurons are recruited dynamically. Specifically, it is not known whether the two types of interneurons are recruited differently during high-frequency GC inputs (Jörntell and Ekerot, 2006).…”