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Results for “CEREBELLAR CORTEX”

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At least 1,009 records · Page 56Linked to original sources
PubMed2000

Temporal coupling between neuronal activity and blood flow in rat cerebellar cortex as indicated by field potential analysis.

1. Laser-Doppler flowmetry and extracellular recordings of field potentials were used to examine the temporal coupling between neuronal activity and increases in cerebellar blood flow (CeBF). 2. Climbing fibre-evoked increases in CeBF were dependent on stimulus duration, indicating that increases in CeBF reflected a time integral in neuronal activity. The simplest way to represent neuronal activity over time was to obtain a running summation of evoked field potential amplitudes (runSigmaFP). RunSigmaFP was calculated for each stimulus protocol and compared with the time course of the CeBF responses to demonstrate coupling between nerve cell activity and CeBF. 3. In the climbing fibre system, the amplitude and time course of CeBF were in agreement with the calculated postsynaptic runSigmaFP (2-20 Hz for 60 s). This suggested coupling between CeBF and neuronal activity in this excitatory, monosynaptic, afferent-input system under these conditions. There was no correlation between runSigmaFP and CeBF during prolonged stimulation. 4. Parallel fibre-evoked increases in CeBF correlated with runSigmaFP of pre- and postsynaptic potentials (2-15 Hz for 60 s). At higher stimulation frequencies and during longer-lasting stimulation the time course and amplitudes of CeBF responses correlated with runSigmaFP of presynaptic, but not postsynaptic potentials. This suggested a more complex relationship in this mixed inhibitory-excitatory, disynaptic, afferent-input system. 5. This study has demonstrated temporal coupling between neuronal activity and CeBF in the monosynaptic, excitatory climbing-fibre system. In the mixed mono- and disynaptic parallel fibre system, temporal coupling was most clearly observed at low stimulation frequencies. We propose that appropriate modelling of electrophysiological data is needed to document functional coupling of neuronal activity and blood flow.

Action Potentials↗
PubMed2001

Control of Ca(2+) influx by cannabinoid and metabotropic glutamate receptors in rat cerebellar cortex requires K(+) channels.

1. In the rodent cerebellum, both presynaptic CB1 cannabinoid receptors and presynaptic mGluR4 metabotropic glutamate receptors acutely depress excitatory synaptic transmission at parallel fibre-Purkinje cell synapses. Using rat cerebellar slices, we have analysed the effects of selective CB1 and mGluR4 agonists on the presynaptic Ca(2+) influx which controls glutamate release at this synapse. 2. Changes in presynaptic Ca(2+) influx were determined with the Ca(2+)-sensitive dyes fluo-4FF AM or fluo-3 AM. Five stimulations delivered at 100 Hz or single stimulations of parallel fibres evoked rapid and reproducible transient increases in presynaptic fluo-4FF or fluo-3 fluorescence, respectively, which decayed to prestimulus levels within a few hundred milliseconds. Bath application of the selective CB1 agonist WIN55,212-2 (1 microM) markedly reduced the peak amplitude of these fluorescence transients. This effect was fully reversed by the selective CB1 antagonist SR141716-A (1 microM). 3. Bath application of the selective mGluR4 agonist L-AP4 (100 microM) also caused a transient decrease in the peak amplitude of the fluorescence transients evoked by parallel fibre stimulation. 4. Bath application of the potassium channel blocker 4-AP (1 mM) totally prevented both the WIN55,212-2- and the L-AP4-induced inhibition of peak fluorescence transients evoked by parallel fibre stimulation. 5. The present study demonstrates that activation of CB1 and mGluR4 receptors inhibits presynaptic Ca(2+) influx evoked by parallel fibre stimulation via the activation of presynaptic K(+) channels, suggesting that the molecular mechanisms underlying this inhibition involve an indirect inhibition of presynaptic voltage-gated Ca(2+) channels rather than their direct inhibition.

4-Aminopyridine↗
PubMed2002

Dynamic correlation of neuronal activity in rat cerebellar cortex modulated by behavior.

Sprague-Dawley rats (2-4 months old) were trained to perform a reaching-grasping task while their head was fixated and multielectrode recordings were performed in the ipsilateral cerebellar hemisphere. Multiunit (MU) activity was recorded with 2-3 electrodes in the Purkinje cell layer at various depths (1.5-4.5 mm) from the pial surface while the animal either performed the reaching-grasping task or was at rest. Recording sites were visually aligned along the transverse or the sagittal axis of Crus IIa. Excess correlations of MU spike activity were calculated at 10-ms time resolution using the joint peristimulus time histogram (JPSTH), to reveal the dynamics of cross-correlations corrected for nonstationarities in spike rates. Peak correlation amplitudes and areas were calculated separately for a time period preceding the movement and for a succeeding period during which the movement occurred. Correlations were compared across different paradigms: transversal versus sagittal alignment of recordings sites and behavior versus rest. No significant differences were found between transversally and sagittally aligned recording sites. Significant differences in peak correlation amplitude and/or peak area, however, were found both between premovement and movement time, as well as between both these time periods and periods while the animal was at rest.

Action Potentials↗