Ethanol Modulates the Spontaneous Complex Spike Waveform of Cerebellar Purkinje Cells Recorded in vivo in Mice.

Cerebellar Purkinje cells (PCs) are sensitive to ethanol, but the effect of ethanol on spontaneous complex spike (CS) activity in these cells in vivo is currently unknown. Here, we investigated the effect of ethanol on spontaneous CS activity in PCs in urethane-anesthetized mice using in vivo patch-clamp recordings and pharmacological manipulation. Ethanol (300 mM) induced a decrease in the CS-evoked pause in simple spike (SS) firing and in the amplitude of the afterhyperpolarization (AHP) under current clamp conditions. Under voltage-clamp conditions, ethanol significantly decreased the area under the curve (AUC) and the number of CS spikelets, without changing the spontaneous frequency of the CSs or the instantaneous frequency of the CS spikelets. Ethanol-induced a decrease in the AUC of spontaneous CSs was concentration dependent. The EC50 of ethanol for decreasing the AUC of spontaneous CSs was 168.5 mM. Blocking N-methyl-D-aspartate receptors (NMDARs) failed to prevent the ethanol-induced decreases in the CS waveform parameters. However, blockade of cannabinoid receptor 1 (CB1) significantly suppressed the ethanol-induced effects on the CS-evoked pause in SS firing, amplitude of the AHP, spikelet number and the AUC of CSs. Moreover, a CB1 receptor agonist not only reduced the number of spikelets and the AUC of CSs, but also prevented the ethanol-induced inhibition of CS activity. Our results indicate that ethanol inhibits CS activity via activation of the CB1 receptor in vivo in mice, suggesting that excessive ethanol intake inhibits climbing fiber (CF)-PC synaptic transmission by modulating CB1 receptors in the cerebellar cortex.

Anatomical and functional relationships between deep cerebellar nuclei and cerebellar cortical Crus II in vivo in mice.

We previously reported that an air-puff stimulation on the ipsilateral whisker pad evoked responses in molecular layer (ML) and Purkinje cell (PC) layer in cerebellar cortex folium Crus II. We used anterograde tracing and electrophysiological methods to investigate the anatomical and functional relationships between the trigeminal tactile response area in the cerebellar cortex Crus II and deep cerebellar nuclei (DCN) in living mice. We found that the axons of tactile activated PCs projected in anterior part (IntA) and posterior part (IntP), and dorsolateral hump (IntDL) of ipsilateral interposed cerebellar nucleus (ICN). In ICN, the tactile stimulus evoked-field potential expressed a sequence of two negative components N1 and N2, while extracellular recordings from ICN neurons revealed that an increase in spike frequency in response to tactile stimulus. When the duration of facial air-puff stimulus were ≥ 30 ms, stimulation off response (Roff) were observed in the ICN, but an increase in the duration of facial air-puff stimulation did not significantly affect the amplitude of Ron (N1 and N2) and Roff. The latency and time to peak of N1 in ICN were significantly shorter than that of N1 in the ML, but the latency and time to peak of N2 in ICN were significantly later than that of P1 in the ML. The present results suggest that the facial sensory information, at least in part, is transferred to ICN by PC axons from Crus II, which evokes excitation in ICN neurons.

Effects of Propofol on the Dynamic Properties of Sensory Information Processing in the Mouse Cerebellar Cortical Molecular Layer in vivo.

Propofol is a global central nervous system depressant that affects information processing in the central nervous system. However, the effects of propofol on sensory information processing in the cerebellar cortical molecular layer are unknown. In this study, we examined the effects of propofol on the dynamics of sensory stimulation-evoked responses in the cerebellar molecular layer in urethane-anesthetized mice, using electrophysiological and pharmacological methods. Our results showed that cerebellar surface perfusion of propofol (10-1,000 µmol/l) significantly decreased amplitude and area under the curve (AUC) of the sensory stimulation-evoked inhibitory component (P1) but increased the rise time and decay time of P1. In contrast, administration of propofol significantly enhanced the sensory stimulation-evoked excitatory component (N1), which exhibited increases in amplitude and AUC, as well as increases in rise time and decay time. By blocking the GABAA receptor activity, propofol failed to increase the amplitude and the AUC of the excitatory postsynaptic component (N2) of PCs. Our present results suggest that propofol modulates the dynamic properties of the sensory information processing in the cerebellar molecular layer through the modulation of GABAA receptors activity in the adult mouse.

Propofol depresses cerebellar Purkinje cell activity via activation of GABA(A) and glycine receptors in vivo in mice.

Propofol is an intravenous sedative-hypnotic agen, which causes rapid and reliable loss of consciousness. Under in vitro conditions, propofol activates GABAA and glycine receptors in spinal cord, hippocampus and hypothalamus neurons. However, the effects of propofol on the cerebellar neuronal activity under in vivo conditions are currently unclear. In the present study, we examined the effects of propofol on the spontaneous activity of Purkinje cells (PCs) in urethane-anesthetized mice by cell-attached recording and pharmacological methods. Our results showed that cerebellar surface perfusion of propofol (10-1000 µM) induced depression of the PC simple spike (SS) firing rate in a dose-dependent manner, but without significantly changing the properties of complex spikes (CS). The IC50 of propofol for inhibiting SS firing of PCs was 144.5 µM. Application of GABAA receptor antagonist, SR95531 (40 µM) or GABAB receptor antagonist, saclofen (20 µM), as well as glycine receptor antagonist, strychnine (10 µM) alone failed to prevent the propofol-induced inhibition of PCs spontaneous activity. However, application the mixture of SR95531 (40 µM) and strychnine (10 µM) completely blocked the propofol-induced inhibition of PC SS firing. These data indicated that cerebellar surface application of propofol depressed PC SS firing rate via facilitation of GABAA and functional glycine receptors activity in adult cerebellar PCs under in vivo conditions. Our present results provide a new insight of the anesthetic action of propofol in cerebellar cortex, suggesting that propofol depresses the SS outputs of cerebellar PCs which is involved in both GABAA and glycine receptors activity.