Three-Dimensional Heterogeneity of Cerebellar Interposed Nucleus-Recipient Zones in the Thalamic Nuclei.

The cerebellum is conceptualized as a processor of complex movements and is also endowed with roles in cognitive and emotional behaviors. Although the axons of deep cerebellar nuclei are known to project to primary thalamic nuclei, macroscopic investigation of the characteristics of these projections, such as the spatial distribution of recipient zones, is lacking. Here, we studied the output of the cerebellar interposed nucleus (IpN) to the ventrolateral (VL) and centrolateral (CL) thalamic nuclei using electrophysiological recording in vivo and trans-synaptic viral tracing. We found that IpN stimulation induced mono-synaptic evoked potentials (EPs) in the VL but not the CL region. Furthermore, both the EPs induced by the IpN and the innervation of IpN projections displayed substantial heterogeneity across the VL region in three-dimensional space. These findings indicate that the recipient zones of IpN inputs vary between and within thalamic nuclei and may differentially control thalamo-cortical networks.

Sinusoidal stimulation on afferent fibers modulates the firing pattern of downstream neurons in rat hippocampus.

Electrical stimulation in the brain is an emerging therapy for treating a wide range of neurological disorders. Although electrical pulses are commonly used in the clinic, other electrical waveforms such as sinusoidal-waves have been investigated to improve the therapeutic efficacy, to reduce the risk of tissue damage induced by stimulation, and to decrease the consumption of electrical energy. However, the effects of sinusoidal stimulation on neuronal activity are still unclear. In the present study, we investigated the neuronal responses to the stimulation of 50-Hz sinusoidal-waves applied on the afferent fibers of the neurons in the hippocampal CA1 region of Sprague-Dawley rat in vivo. Results show that the stimulation increased the firing rate of both pyramidal neurons and interneurons in the downstream region of stimulation. Also, the stimulation eliminated the original theta rhythms (2-5 Hz) in the single-unit activity of the two types of neurons and entrained these neurons to fire at the stimulation rhythm. These results provide new clues for the mechanisms of brain stimulation to suppress the pathological rhythms in the neuronal activity, and for the application of sinusoidal waveforms in brain stimulation therapy.

Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus.

Dysfunction of inhibitory synaptic transmission can destroy the balance between excitatory and inhibitory synaptic inputs in neurons, thereby inducing epileptic activity. The aim of the paper is to investigate the effects of successive excitatory inputs on the epileptic activity induced in the absence of inhibitions. Paired-pulse orthodromic and antidromic stimulations were used to test the changes in the evoked responses in the hippocampus. Picrotoxin (PTX), γ-aminobutyric acid (GABA) type A (GABA(A)) receptor antagonist, was added to block the inhibitory synaptic transmission and to establish the epileptic model. Extracellular evoked population spike (PS) was recorded in the CA1 region of the hippocampus. The results showed that the application of PTX induced a biphasic change in the paired-pulse ratio of PS amplitude. A short latency increase of the second PS (PS2) was later followed by a reappearance of PS2 depression. This type of depression was observed in both orthodromic and antidromic paired-pulse responses, whereas the GABAergic PS2 depression [called paired-pulse depression (PPD)] during baseline recordings only appeared in orthodromic-evoked responses. In addition, the depression duration at approximately 100 ms was consistent with a relative silent period observed within spontaneous burst discharges induced by prolonged application of PTX. In conclusion, the neurons may ignore the excitatory inputs and intrinsically generate bursts during epileptic activity. The depolarization block could be the mechanisms underlying the PPD in the absence of GABA(A) inhibitions. The distinct neuronal responses to stimulations during different epileptic stages may implicate the different antiepileptic effects of electrical stimulation.

Effects of carnosine on the evoked potentials in hippocampal CA1 region.

OBJECTIVE: To directly examine the effects of carnosine on neuronal excitation and inhibition in rat hippocampus in vivo. METHODS: Artificial cerebrospinal fluid with carnosine was directly administrated over the exposed rat hippocampus. The changes of neuron activity in the CA1 region of hippocampus were evaluated by orthodromically- and antidromically-evoked potentials, as well as paired-pulse stimulation paradigm. RESULTS: In both orthodromic and antidromic response potentials, carnosine transformed population spikes (PSs) with single spike into epileptiform multiple spikes. In addition, similar to the effect of (-aminobutyric acid(A) (GABA(A)) antagonist picrotoxin, carnosine decreased paired-pulse stimulating depression significantly. However, no significant change was observed in the spontaneous field potentials during the application of carnosine. CONCLUSION: The results indicate a disinhibition-induced excitation effect of carnosine on the CA1 pyramidal neurons. It provides important information against the application of carnosine as a potential anticonvulsant in clinical treatment.

Analysis of rat electroencephalogram during slow wave sleep and transition sleep using wavelet transform.

The dynamic features of rat EEGs collected during slow wave sleep (SWS) and transition sleep (TS) were investigated in both time and frequency domains using wavelet transform based on multi-resolution signal decomposition. EEGs of freely moving rats were recorded with implanted electrodes and then decomposed into four components of delta, theta, alpha and beta using wavelet transform. The power and power percentage of each component were calculated as functions of time. In SWS EEGs, the results showed that there existed as much as 26.2% +/- 7.7% time duration in which the delta power percentage was less than 50%. In addition, the powers of other three components in small delta EEGs were significantly larger than those in large delta EEGs. This result revealed a reciprocal relationship between delta oscillation and spindle oscillation. Comparatively, the conventional method of FFT based power spectrum could only show a delta power-dominating (70.6% +/- 6.4%) spectrum of SWS EEGs. In the non-stationary TS EEG, spindle and non-spindle segments were distinguished based on the wavelet components of theta and alpha, and then the average duration of the spindles was estimated. In conclusion, the wavelet transform may be useful in developing novel quantitative time-frequency measures of sleep EEGs as valuable complements of conventional FFT method to analyze the transient changes in sleep EEGs induced by physiological, pathological or pharmacological conditions.

[A study of complexity and power spectrum of cortical EEG and hippocampal potential in rats under different behavioral states].

Objective. To study the complexity and the power spectrum of cortical EEG and hippocampal potential in rats under waking and sleep states. Method. Cortical EEG and hippocampal potential were collected by implanted electrodes in freely moving rats. Algorithmic complexity (Kc), approximate entropy (ApEn), power spectral density (PSD) and gravity frequency of PSD of the potential waves were calculated. Result. The complexity of hippocampal potential was higher than that of cortical EEG under every state. The complexity of cortical EEG was lowest under the state of non rapid eye movement (NREM) sleep. The complexity of hippocampal potential was highest under waking state. The total power of both potentials in 0.5- 30 Hz frequency band showed their highest values under NREM state. Conclusion. The values of Kc and ApEn are closely related to the distributions of PSD. When there are evident peaks in PSD, the complexities of signals will decrease. The complexities may be used to distinguish the difference between cortical EEG and hippocampal potential, or large differences between the same kind of potentials under different behavioral states.

[Sedative and anticonvulsant effect of jujuboside A]

OBJECTIVE: To study the sedative effects of Jujuboside A (JuA) on the Central Nervous System of mice. METHODS: Using a novel jiggle-cage test, we compared the sedative effect of JuA with that of Diazepam (DZP) both with a single and cumulative dose of JuA. We also assessed the anticonvulsant effect of JuA on pentylenetetrazol (PTZ)-induced seizures in mice. RESULTS: JuA significantly decreased total activity intensity and increased the quiet state time of mice. The sedative effects of JuA were more stable and more lasting than that of DZP. However, JuA failed to resist and delay the induced seizure activity in mice. CONCLUSION: Though JuA has sedative effects on mice CNS, it has no anticonvulsant effect on PTZ-induced seizures.