The relationship of post-stimulus time and interval histograms to the timming characteristics of spike trains.

PST (post-stimulus time) and interval histograms computed from recorded spike trains are related to an average timing characteristics of the spike train. The exact nature of this relationship varies with recording parameters, interfering signals, the histogram bin width, and the duration of the measurement interval. This work describes the conditions under which a PST histogram can serve as an unbiased estimate of the ensemble average of a spike train's intensity and an interval histogram can serve as an unbiased estimate of the probability density function of the interspike intervals. Simulation studies are used to confirm the validity of the theoretical results. As an example of an application, these results are used to analyze recordings of singleunit activity in the eight cranial nerve.     

Oscillatory neural networks in the rabbit hippocampus

A model is described to account for damped oscillatory activity of two interacting neural populations, pyramidal cells and interneurons. This network in the hippocampus is treated as a lumped system with tine delays between elements. The physiological mechanism underlying the oscillatory activity appears to involve neural population interaction and cannot be described in terms of a network composed of but two neurons, a single pyramidal cell and a single interneuron. An unusual aspect of the model is the explicit incorporation of an ongoing background input to raise the mean level of activity of the pyramidal cell population. This model has evolved from a series of studies previously performed on cats. To test the model experiments were performed on rabbits. The data showing oscillatory activity following fornix stimulation in the rabbit indicate that the model can be applied not only to the cat but also to the rabbit. In additions, for commissural stimulation oscillatory potentials of neural populations and individual pyramidal cells were evoked as predicted by the model.     

Thermal dependence of neural activity in the hamster hippocampal slice preparation

1. Neural activity was recorded in an in vitro hamster hippocampal slice preparation while the temperature of the Ringer's solution bathing in the slice was controlled at selected levels. 2. The amplitude of the population spike (action potentials from a group of pyramidal cells) was measured as bath temperature was lowered from 35 degrees C to temperatures where a response could not be evoked. 3. Plots of population spike amplitude versus temperature have bell-shaped curves. The population spikes increased in amplitude as temperature was lowered from 35 degrees C, reached a peak amplitude between 25 and 20 degrees C, and then decreased until a response could not be evoked when temperature was further lowered. 4. These in vitro results obtained in the slice preparation are related to in vivo hippocampal studies. Results are interpreted as consistent with the proposal reviewed here that neural activity in the hippocampus plays a role at specific stages of entrance into and arousal from hibernation.     

Assessment of the Reliability of Amplitude Histograms for Inhibitory Synaptic Currents in Rat Cortex Culture

We analyzed in detail the quantum parameters of evoked inhibitory postsynaptic currents (eIPSC) recorded from synaptically connected cultured cortex neurons using a whole-cell patch-clamp technique. The IPSC were evoked using minimum extracellular stimulation of a presynaptic unit with a frequency of 0.2 sec^-1 at the holding potential of -80 mV. Amplitude histograms for eIPSC demonstrated clearly detectable equally spaced peaks. For each histogram, we used a method based on autocorrelation analysis and Monte Carlo simulation to determine whether peaks in the amplitude histograms can result due to finite sampling from the sum of the Gaussian distributions. The autocorrelation function allowed us to measure the peak spacing (and, hence, the mean quantum size) for each histogram; this parameter was found to be 10 pA.     

Occurrence of phenolsulfotransferase in primary glial culture cells of rat

Phenolsulfotransferase (PST) activity towards phenol and monoamines was determined in rat brain and in primary cultures of rat astrocytes. The pH requirement.K _m values and the proportion of PST activity with respect to phenol and dopamine as substrates were similar between PST from the glial cells and the rat cortex. The enzyme activity increased with age in the brain of older animals, and also with increasing incubation time in the primary culture of astroglia. The specific PST activity of the astroglia appeared to be higher than that of the brain enzyme. In glial cultures treated with 0.25 mM dibutyryl cyclic AMP in the same culture conditions, PST activity is suppressed to about 25% of its untreated counterpart, even though dibutyryl cyclic AMP at concentrations of 1 mM only slightly inhibited PST activity in vitro.     

Selective GABAergic control of higher-order thalamic relays

GABAergic signaling is central to the function of the thalamus and has been traditionally attributed primarily to the nucleus reticularis thalami (nRT). Here we present a GABAergic pathway, distinct from the nRT, that exerts a powerful inhibitory effect selectively in higher-order thalamic relays of the rat. Axons originating in the anterior pretectal nucleus (APT) innervated the proximal dendrites of relay cells via large GABAergic terminals with multiple release sites. Stimulation of the APT in an in vitro slice preparation revealed a GABA(A) receptor-mediated, monosynaptic IPSC in relay cells. Activation of presumed single APT fibers induced rebound burst firing in relay cells. Different APT neurons recorded in vivo displayed fast bursting, tonic, or rhythmic firing. Our data suggest that selective extrareticular GABAergic control of relay cell activity will result in effective, state-dependent gating of thalamocortical information transfer in higher-order but not in first-order relays.     

The temporal organization of the functional connection of the motor cortex neurons in the cat]

Conditioned food-procuring response to time (2 minutes interval) was elaborated in cats, multiunit activity of the motor cortex being recorded. On the basis of single spike trains discriminated from the multiunit activity the cross-correlation histograms were built and the spikes composing their peaks were analysed in real time. This secondary analysis of the histograms allowed to ascertain the dynamics of functional connections between the neurons during the phase of active waiting according to the distribution of coincident impulses. A concentration of coincident impulses of simultaneously recorded cells was observed in different moment of time. In some neuronal pairs the concentration of coincident impulses was revealed to the end of the conditioned interval. The data obtained are considered as a manifestation of the conditioned reaction at the level of neuronal interaction.     

Pancreastatin,a chromogranin A-derived peptide,activates protein synthesis signaling cascade in rat adipocytes

Pancreastatin (PST), a chromogranin A-derived peptide, has been found to modulate glucose, lipid, and protein metabolism in rat adipocytes. PST has an overall counterregulatory effect on insulin action by activating a specific receptor-effector system (Galpha(q/11) protein-PLC-beta-PKC(classical)). However, PST stimulates both basal and insulin-mediated protein synthesis in rat adipocytes. In order to further investigate the mechanisms underlying the effect of PST stimulating protein synthesis, we sought to study the regulation of different components of the core translational machinery by the signaling triggered by PST. Thus, we studied ribosomal p70 S6 kinase, phosphorylation of the cap-binding protein (initiation factor) eIF4E, and phosphorylation of the eIF4E-binding protein 4E-BP1 (PHAS-I). We have found that PST stimulates the S6 kinase activity, as assessed by kinase assay using specific immunoprecipitates and substrate. This effect was checked by Western blot with specific antibodies against the phosphorylated S6 kinase. Thus, PST dose-dependently stimulates Thr421/Ser424 phosphorylation of S6 kinase. Moreover, PST promotes phosphorylation of regulatory sites in 4E-BP1 (PHAS-I) (Thr37, Thr46). The initiation factor eIF4E itself, whose activity is also increased upon phosphorylation, is phosphorylated in Ser209 by PST stimulation. Finally, we have found that these effects of PST on S6 kinase and the translation machinery can be blocked by preventing the activation of PKC. These results indicate that PST stimulates protein synthesis machinery by activating PKC and provides some evidence of the molecular mechanisms involved, i.e., the activation of S6K and the phosphorylation of 4E-BP1 (PHAS-I) and the initiation factor eIF4E.     

Effects of substance P analogues on spinal dorsal horn neurons

The effects of iontophoretically applied (D-Pro2, D-Phe7, D-Trp9)-SP and (D-Pro2, D-Trp7,9)-SP on the spontaneous and evoked activity of functionally identified cat spinal dorsal horn neurons have been investigated in vivo by means of extracellular single unit recording technique. In addition, the rat spinal cord slice preparation has been used to study the actions of (D-Pro2, D-Trp7,9)-SP and (D-Arg1, D-Pro2, D-Trp7,9, Leu11)-SP on the resting membrane potential of dorsal horn neurons and also on their responses to dorsal root stimulation and exogenous SP application. We have observed that both (D-Pro2, D-Phe7, D-Trp9)-SP and (D-Pro2, D-Trp7,9)-SP produced an excitation of about 15% of all neurons tested and had a weak antagonistic effect against SP in the cat spinal cord. (D-Pro2, D-Trp7,9)-SP suppressed the SP-induced excitation in 63% of examined cells. In addition, depression of the glutamate-induced excitation and spontaneous activity was evident in 10% and 19% of the cat dorsal horn neurons tested, respectively. In the spinal cord slice preparation (D-Arg1, D-Pro2, D-Trp7,9, Leu11)-SP proved to be a more potent antagonist of the SP-induced depolarization and the dorsal root-elicited slow depolarization, if compared with (D-Pro2, D-Trp7,9)-SP.     

Dissociation of parathyroid hormone and cyclic-3', 5'AMP effects on Na-Pi uptake by cells isolated from proximal straight tubules of rat kidney.

Studies in respiratory alkalotic or short-term phosphate deprived rats raised the possibility that in straight portion of proximal tubules (PST) cAMP might be not a mediator of PTH in inhibition of phosphate reabsorption. The present experiments directly compared the sensitivity of Na-dependent phosphate [32P] (Na-Pi) uptake to PTH or cAMP by PCT or PST cells freshly prepared from outer cortex and outer stripe of outer medulla of rat kidney. The purity of the cells was examined by activity of enzymes specific for PST i.e. glutamine synthetase, gamma-glutamyl transpeptidase and creatine kinase, a marker enzyme for medullary thick ascending limb (MTAL) and distal convoluted tubule. Similar inhibition of Na-Pi uptake by 1-34 bPTH by PST and PCT cells was observed: -33.0 and -30.0% (ns), respectively. In contrast, dibutyryl cAMP decreased Na-Pi uptake only by PCT but not by PST cells: -31.0 and -3.6% (p<0.02), respectively. The 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, resulted in slight stimulation of Na-Pi uptake by PST but strong inhibition by PCT cells: 7.8 vs -26.0% (p<0.001). In contrast to PCT in PST cells cAMP seems to play a minor role as a mediator of inhibition of Na-Pi uptake by PTH.     

Negative relationship between odor-induced spike activity and spontaneous oscillations in the primary olfactory system of the terrestrial slug Limax marginatus

Although primary olfactory systems in various animals display spontaneous oscillatory activity, its functional significance in olfactory processing has not been elucidated. The tentacular ganglion, the primary olfactory system of the terrestrial slug Limax marginatus, also displays spontaneous oscillatory activity at 1-2 Hz. In the present study, we examined the relationship between odor-evoked spike activity and spontaneous field potential oscillations in the tentacular nerve, representing the pathway from the primary olfactory system to the olfactory center. Neural activity was recorded from the tentacular nerve before, during and after application of various odors (garlic, carrot, and rat chow) to the sensory epithelium and the changes in firing rate and spontaneous oscillations were analyzed. We detected the baseline amplitude of the oscillations and baseline spike activity before stimulation. Odor stimulations for 20 s or 60 s evoked a transient increase in the firing rate followed by a decrease in the amplitude of spontaneous oscillations. The decrease in the amplitude was larger in the first 8 s of stimulation and subsequently showed recovery during stimulation. The amplitude of the recovered oscillations often fluctuated. Odor-evoked spikes appeared when the amplitude of the recovered oscillations was transiently small. These results suggest that the large oscillations could inhibit spike activity whereas the first transient increase in spike activity was followed by the decrease in the oscillation amplitude. Our results indicate that there is a significant negative correlation between spontaneous oscillations and odor-evoked spike activity, suggesting that the spontaneous oscillations contribute to the olfactory processing in slugs.     

Electrical activity and intraluminal pressure of the cauda epididymidis of the rat

Smooth muscle electrical activity was recorded simultaneously with intraluminal pressure in the cauda epididymidis and epididymal vas of the rat in vitro. Spontaneous electrical activity spread over distances of several centimetres and was associated with a pressure wave recorded through an open-ended catheter in the distal cauda and epididymal vas. Transmission of pressure wave was gradually damped by filling of the catheter with spermatozoa.     

Evoked frequency stabilization in the electrical activity of the cat brain

In this study, our previous results on the important relation between EEG and EPs were extended by experiments with chronically implanted and freely moving cats, which had electrodes at the acoustical cortex, inferior colliculus and reticular formation. During the experiments the frequency stabilization upon sound stimulation was shown in the frequency domain by comparison of the pre-stimulus power spectra and post-stimulus amplitude frequency characteristics. Comparative frequency domain analysis of about 75 EEG-EPograms (sample of spontaneous activities just prior to stimulation and single evoked potentials following the stimulation), which were recorded from all the brain nuclei mentioned above and from each of the 11 cats, was performed as follows: 1) Power spectra of the EEG-records prior to stimulus were evaluated. 2) Instantaneous frequency characteristics of single EPs were obtained by the Fourier transform. 3) Distribution of the amplitude maxima of the EP-frequency characteristics and the distribution of the EEG-spectral peaks were compared by plotting two types of histograms containing relevant spectral peaks before and after the stimulation. In a frequency range between 1–1000 Hz, the frequency distribution of the EP records from RF and IC were accumulated in narrow discrete frequency channels, whereas, the distribution of the spectral peaks of the EEG depicted frequency spread in broad channels. The frequency stabilization of the EP records from GEA, in the alpha frequency range, was also observed. This effect was described by a factor which we called as the Frequency Stabilization Factor. The results presented in this study showed that the frequency stabilization of the brain's electrical activity induced by sensory stimulation displayed a fluctuation leading to frequency stabilization factors between 0.95 and 5.00. The frequency stabilization and relevant power enhancement upon stimulation strongly support our contention that evoked potential results from the frequency stabilization of the spontaneous activity, triggered by stimulation.Supported by Grant No. TAG-345 of the Scientific and Technical Research Council of Turkey     

猫小脑第Ⅶ小叶皮层—核团投射的电生理学研究

在三碘季铵酚制动的去大脑猫上,记录了小脑后叶的第Ⅶ小叶皮层浦肯野细胞(PC)对分别刺激顶核、间位核和齿状核的逆行场电位和逆行单位反应,以确定小脑皮层PC对这三个核团投射的空间分布。在鉴定了PC对其靶核团的投射后,用特制的模拟自然屈腕运动的刺激装置来推动猫同侧前肢的掌背,造成腕关节一次轻微的屈曲,观察该PG对这一刺激的单位反应。实验资料用电子计算机处理,作出平均诱发电位和刺激后时间直方图。 本文以电生理学方法揭示,猫小脑后叶第Ⅶ小叶皮层-核团投射存在较明确的纵区分布模式,纵区之间的分界线走向有一定的弯曲,与前叶略有不同。小脑后叶皮层从中线到两侧2.8mm为顶核区(FZ);其外侧为间位核区(IZ),最大宽度约为3.5mm;齿状核区(DZ)约始于5.0mm处。这三个不同纵区的PC对外周自然屈腕刺激都有反应,但反应细胞的百分数不同,FZ有59％的PC对外周刺激有反应,IZ为84％,DZ为20％。这些结果表明后叶第Ⅶ小叶具有类似于前叶的功能分布,IZ的PC对外周刺激有更大的调制作用,提示该皮层-核团投射的纵区结构有其特定的功能意义。     

The effects of synaptic noise on measurements of evoked excitatory postsynaptic response amplitudes.

Spontaneously occurring synaptic events (synaptic noise) recorded intracellularly are usually assumed to be independent of evoked postsynaptic responses and to contaminate measures of postsynaptic response amplitude in a roughly Gaussian manner. Here we derive analytically the expected noise distribution for excitatory synaptic noise and investigate its effects on amplitude histograms. We propose that some fraction of this excitatory noise is initiated at the same release sites that contribute to the evoked synaptic event and develop an analytical model of the interaction between this fraction of the noise and the evoked postsynaptic response amplitude. Recording intracellularly with sharp microelectrodes in the in vitro hippocampal slice preparation, we find that excitatory synaptic noise accounts for up to 70% of the intracellular recording noise, when inhibition is blocked pharmacologically. Up to 20% of this noise shows a significant correlation with the evoked event amplitude, and the behavior of this component of the noise is consistent with a model which assumes that each release site experiences a refractory period of approximately 60 ms after release. In contrast with classical models of quantal variance, our models predict that excitatory synaptic noise can cause the apparent variance of successive peaks in an excitatory synaptic amplitude histogram to decrease from left to right, and in some cases to be less than the variance of the measured noise.     

Phase-Dependent Effects of Stimuli Locked to Oscillatory Activity in Cultured Cortical Networks

The archetypal activity pattern in cultures of dissociated neurons is spontaneous network-wide bursting. Bursts may interfere with controlled activation of synaptic plasticity, but can be suppressed by the application of stimuli at a sufficient rate. We sinusoidally modulated (4 Hz) the pulse rate of random background stimulation (RBS) and found that cultures were more active, burst less frequently, and expressed oscillatory activity. Next, we studied the effect of phase-locked tetani (four pulses, 200 s⁻¹) on network activity. Tetani were applied to one electrode at the peak or trough of mRBS stimulation. We found that when tetani were applied at the peak of modulated RBS (mRBS), a significant potentiation of poststimulus histograms (PSTHs) occurred. Conversely, tetani applied at the trough resulted in a small but insignificant depression of PSTHs. In addition to PSTHs, electrode-specific firing rate profiles within spontaneous bursts before and after mRBS were analyzed. Here, significant changes in firing rate profiles were found only for stimulation at the peak of mRBS. Our study shows that rhythmic activity in culture is possible, and that the network responds differentially to strong stimuli depending on the phase at which they are delivered. This suggests that plasticity mechanisms may be differentially accessible in an oscillatory state.     

High-resolution optical control of spatiotemporal neuronal activity patterns in zebrafish using a digital micromirror device

Optogenetic approaches allow the manipulation of neuronal activity patterns in space and time by light, particularly in small animals such as zebrafish. However, most techniques cannot control neuronal activity independently at different locations. Here we describe equipment and provide a protocol for single-photon patterned optical stimulation of neurons using a digital micromirror device (DMD). This method can create arbitrary spatiotemporal light patterns with spatial and temporal resolutions in the micrometer and submillisecond range, respectively. Different options to integrate a DMD into a multiphoton microscope are presented and compared. We also describe an ex vivo preparation of the adult zebrafish head that greatly facilitates optogenetic and other experiments. After assembly, the initial alignment takes about one day and the zebrafish preparation takes <30 min. The method has previously been used to activate channelrhodopsin-2 and manipulate oscillatory synchrony among spatially distributed neurons in the zebrafish olfactory bulb. It can be adapted easily to a wide range of other species, optogenetic probes and scientific applications.     

Analysis of extracellular potentials using an IBM PC

1. A system has been developed for using IBM PC-compatible computers in combination with a Grafitek Data Logging Interface to record spike trains on magentic discs for later analysis. 2. The times and amplitudes of spikes detected on two input channels are recorded, together with a third channel containing information on computer-generated stimuli and keyboard-activated event markers. In excess of 50,000 spikes can be recorded with a computer having 640 k of Random Access Memory. 3. The recorded spike trains can be reconstructed on the computer monitor and keyboard-controlled window discriminators can be used to select the spikes for analysis by amplitude. 4. The same recorded data can be analysed to produce displays of spike count against time, amplitude histograms, inter-spike interval histograms, peri-stimulus time histograms(PSTH), raster displays and auto- and cross-correlations between activity on the two channels. Each spike is identified by number, allowing easy location of the start and finish of the section of data to be analysed, and the PSTH, raster and correlation analyses allow pretriggering to investigate event occurring before stimulation. 5. The axes of the displays histograms can be adjusted to produce optimum displays, and hard copy can be produced on dot matrix printers or digital plotters. 6. Quantitative analysis enables comparison between different recordings and treatments.     

新生大鼠大脑皮层神经元胞体ATP激活的离子通道及其特性

用膜片箝技术的细胞贴附式和内面向外式,在机械分离的新生ＳＤ大鼠的大脑皮层神经元上,记录到ＡＴＰ激活的离子通道。此通道的电导为３２ｐＳ,对Ｎａ~＋,Ｋ~＋和Ｃｓ~＋无选择性通透,而对Ｃｌ~－不通透。通道开放时间分布直方图多数需用双指数拟合,少数可用单指数拟合;通道关闭时间分布直方图均需用双指数拟合。通道的平均开放时间和开放概率均不依赖于膜电位;但通道的开放概率随着激动剂ＡＴＰ浓度的增加而增大。当电极内液无ＡＴＰ时,无通道电流。六烃季胶和美加明不能阻断此通道。上述结果表明,新生大鼠的大脑皮层神经元胞体可能存在ＡＴＰ激活的离子通道。     

Subthalamic local field beta oscillations during ongoing deep brain stimulation in Parkinson's disease in hyperacute and chronic phases

In the past years, local field potential (LFP) signals recorded from the subthalamic nucleus (STN) in patients undergoing deep brain stimulation (DBS) for Parkinson's disease (PD) disclosed that DBS has a controversial effect on STN beta oscillations recorded 2-7 days after surgery for macroelectrode implantation. Nothing is known about these DBS-induced oscillatory changes 30 days after surgery. We recorded STN LFPs during ongoing DBS in 7 patients with PD, immediately (hyperacute phase) and 30 days (chronic phase) after surgery. STN LFP recordings showed stationary intranuclear STN beta LFP activity in hyperacute and chronic phases, confirming that beta peaks were also present in chronic recordings. Power spectra of nuclei with significant beta activity (54% of the sample) showed that it decreased significantly during DBS (p=0.021) under both recording conditions. The time course of beta activity showed more evident DBS-induced changes in the chronic than in the hyperacute phase (p=0.014). DBS-induced changes in STN beta LFPs in patients undergoing DBS in chronic phase provide useful information for developing a new neurosignal-controlled adaptive DBS system.