Mechanisms Of Tactile Stimulation Evoked Synaptic Transmission And Long-Term Plasticity In Mouse Cerebellar Purkinje Cells

Dynamic properti扮 of sensory informa村on processing 山 mouse cerebellar cortex[Purpose] Sensory information coming from climbing fiber and mossy fiber-granule cell pathways, and generates motor-related outputs according 化 internal ml的 of integration and computation in the cerebellar cortex. When the sensory infonnation transferred in cerebellar cortex that evokes field potential responses in the molecular layer(ML),Purkinje 化11 layer 巧G。and granule cell layer(GCL). However, the dynamic properties of sensory information evoked field potential i*espon巧s in cerebellar cortex arc currently unclear, and the frcqu幻icy prop功ti的 of the cerebellar Purkinje cells 巧G) sensory ir的ponses are unknown. Therefore, we studied the dynamic characterization of sensory stimulation-evoked responses in the cerebellar GCL,ML and PCs by elec仕ophysiological recording and pharmacological methods.[Methods] Following adult(6-8 weeks old) HA/ICR mice were anesthetized with urethane(1.3g/kg) by intraperitoneal injection. After sheared the whiskers, the mice were tracheotomized and fixed on a stereotaxic fiame. After a 1-1.5mm craniotomy was drilled 化 expose the cerebellar surface in correspondence 化 Crus II. The dura mater was carefully removed, and the brain surface was constantly superfused with oxygenated artificial cerebrospinal fliiid(ACSF) with a peristaltic pump. Sensory stimulation on the ipsilateral whisker pad was performed by air-puff(5-500 ms in duration, 60 psi in intensity). Sensory stimulation was synchronized with the electrophysiological recording. Recording electrodes were filled with ACSF, with resistances of 3-5 MQ. Electrophysiological data were analyzed using Clampfit 10.3software. All values are expressed as the mean ± SEM, and 出fferences were evaluated by the Student’s paired Mest or one-way ANOVA using 沈化 17.0software.户 values below 0.05 were considered 化 indicate a statistically significant difference between experimental groups.[Results] ")Air-puff stimulation 口-10 ms in duration) of the *s" ateral whisker-pad evoked single-peak Kspons的 in the GCL and ML; whereas a duration of stimulation 含30 ms in GCL and >60ms in ML, evoked double-peak responses that corresponded with stimulation-on and-off responses via mossy fiber pathway.(2) The highest frequency of stimulation train for evoking GCL responses was 33 Hz.In contrast, the highest frequency of stimulation train for evoking ML iresponses was 4Hz.口)The outp山 of cerebellar PCs could be significantly affected by all p山ses of 化e low-frequency(0.25-2 Hz) sensory stimulation train, but only by the 1。and 2加 pukes of the high-frequency(>4 Hz) sensory stimulation train.(4) Blockade of gamma-aminobutyric acid 1:说eptor A(GABAa) ac杜vity,each pulse of 1 Hz facial stimulation evoked simple spike firing in the PCs, but only the 1®* and2°*^ pulses of 4 Hz stimulation induced an increase in simple spike firing of the PCs.[Conclusions]The cerebellar granule cells transfer the high-frequency and high-fidelity sensory information from mossy fibers,which is cut-off by molecular layer intemeurons(MLIs).(2) GABAa Kceptor-mediated inhibition did not significantly affed the frequency properties of sensory stimulation evoked Kspons的 in the mouse csrebdlar PCs.口) These iresults suggest that the MLIs network acts 贴 a low-pass filter during the processing of high-frequency sensory information, and play a critical role on the sensory-related outputs of PCs in the mouse cerebellar cortex.Tactile stimulation induced the endocannabinoids-dependent GABAergic Long-term depression at cerebellar Purkinje cells in vivo in mice[Purpose] Cerebellar long-term synaptic plasticity has been proposed 化 provide a mechanism for motor learning. Numerous studies have "山strated 化e induction and mechanisms of synaptic plasticity at parallel 扫ber-Purkinje cell(PF-PC),parallel fiber-molecular layer intemeurons(PF-MLI) and mossy fiber-granule cells(MF-GrC)synapses, but the induction and mechanisms of sensory stimulation evoked synaptic plasticity at MLI-PC in cerebellar cortex in living animals are currently unknown.Therefore, we here studied the expression and the mechanism of MLI-PC GABAergic synaptic plasticity induced by train of facial sensory stimulation in urethane-anesthetized mice by eeU-attached Kcording 化chnique and pharmacological methods.IMe化ods] Following adult(6-8-week-old) HA/IC民 mice were anesthetized wi化urethane(1.3 g/kg body weight i.p.). Mice were tracheotomized 化 avoid respiratory obstruction, the craniotomy was drilled to expose the cerebellar surface corresponding!;〇 Crus II. The brain surface was constantly superfiised wi化 oxygenated ACSF wi化 a peristaltic pvimp at 0.5 ml/min. Rectal temperature was monitored and maintained at37.0 ± 0.2°G using body temperature equipment. For induction of MLI-PC synaptic plasticity, 240 pulses air-puff stimulation(10 ms, 60 psi) delivered at 1 Hz^ 2 Hz and 4Hz. The induction stimulation was delivered at 10 minutes after the recording was stable. Values are expressed as the mean ± SEM. ANOVA(posthoc multiple comparison; SPSS software) was used 化 determine 也e level of statistical significance between groups of data. P-values below 0.05 were considered to indicate a statistically sign!扫cant difference between experimental groups.[Results](1) The repetitive facial stimulation at 1 Hz, but not 2 Hz and 4 Hz produced a persistent depr郎sion of MU-FC GABAergic synaptic transmissio打 at MLI-PC sy打江p化s, which accompanied with a dccre犯e in the stimulation-evoked pau化 of spike firing.口)The MLI-PC GABAergic LTD could be prevented by blockade of CBl receptoi*s,andcouldbepharmacologicalinducedbyCBlreceptoragoni^.(3) 1 Hz facial sensory stimulation delivered in the presence of mGluRl ant^onist,JNJl 62巧685 failecHo prevent the MLI-PC GABAergic LTD, whereas blockade of NMDA receptor during 1 Hz facial stimulatioii abolished the expression of MLI-PC GABAergic LTD.[Conclusions]Tactile stimulation could induce an eCB-dependent LTD of GABAergic transmission at MLI-PC synapses via activation of NMDA receptor in cerebellar cortical Crus II in vivo in mice. Our results suggest tiiat the tactile stimulation evoked MLI-PC GABAergic synaptic plasticity might be involved in motor learning in living animals.