Effects of benzodiazepines on single unit activity in the substantia nigra pars reticulata

Intravenous administration of two benzodiazepines, flurazepam and diazepam, had an inhibitory effect on the firing rates of neurons of the substantia nigra pars reticulata, a brain region with an identified GABAergic innervation. Diazepam was more potent than flurazepam. Bicuculline and picrotoxin, two drugs which block GABAergic transmission, and caffeine and theophylline, two methylxanthines which inhibit benzodiazepine binding, all reversed the inhibition produced by diazepam. The action of theophylline was less consistent than that of caffeine. Similarly, Ro 15–1788, an imidazodiazepine which putatively functions as a specific benzodiazepine antagonist, reversed the diazepam-induced inhibition. These findings are consistent with previous reports which suggest that the benzodiazepines may act through a GABAergic mechanism. In a separate group of experiments, caffeine or Ro 15–1788 was administered alone. While caffeine excited all reticulata cells tested. Ro 15–1788, the more specific benzodiazepine antagonist, generally had little excitatory effect. These results suggest: 1) that cells of the substantia nigra pars reticulata may not receive a substantial, tonic inhibition mediated by an endogenous benzodiazepine-like substance; and 2) that the methylxanthines may increase reticulata cell firing, at least in part, through mechanisms unrelated to the blockade of benzodiazepine receptors.     

Analysis of spontaneous unit activity of the cat caudate nucleus

Spontaneous unit activity recorded extracellularly from the caudate nucleus in acute experiments on cats was analyzed. A graph of the sliding mean frequency, an interspike interval histogram, correlogram, intensity function, and histogram of correlation between adjacent intervals were plotted for the spontaneous activity of each neuron. The spontaneous activity of neurons of the caudate nucleus showed considerable variability in time and its mean frequency varied for different neurons from 0.5 to 20 spikes/sec. Depending on the temporal pattern of the spikes and also on the statistical indices, spontaneous unit activity in the caudate nucleus was conventionally divided into two types: single and grouped. A switch from one type of activity to the other was observed for the same neuron. On the basis of the data as a whole it is impossible to regard the spontaneous unit activity of the caudate nucleus as a simple random (Poissonian) spike train.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 369–376, July–August, 1977.     

Effects of decalcification on the membraneous labyrinth

Decalcification of the guinea-pig temporal bone was performed using a solution of 5.5% ethylenediamine tetraacetic acid (EDTA) (14 days) and 5% trichloracetic acid (4 days), respectively.Following the use of EDTA, the general cell structures were well preserved except for a slight distortion of outer hair cells in the organ of Corti. The fine morphology was acceptable though the cell membranes frequently appeared less distinct as compared with controls. Microfilaments/microtubules were preserved in the cells. The substructures of stereocilia and kinocilia can be identified.Decalcification with trichlor acetic acid caused morphological changes at the light microscopical level. The ultrastructure was extremely poor in all cells.For quantification of cochlear hair cells according to the block surface technique, both EDTA and trichlor acetic acid can be used for decalcification with good results.     

电刺激大鼠束旁核对底丘脑核和丘脑腹内侧核神经元的影响

本工作旨在探讨电刺激束旁核（parafascicular nucleus,PF）对帕金森病模型（Parkinson’s disease,PD）大鼠神经行为的改善作用及其机制。成年雄性Sprague—Dawley大鼠黑质致密部注射6一羟基多巴胺建立PD大鼠模型。采用行为学方法观察电刺激PF对阿朴吗啡诱发的大鼠旋转行为的作用,并应用在体细胞外记录法观察电刺激PF对大鼠底丘脑核（subthalamic nucleus,STN）及丘脑腹内侧核（ventromedial nucleus,VM）神经元放电的影响。结果发现,高频电刺激（130Hz,0．4mA,5s）PF一周,明显改善PD大鼠旋转行为。细胞外放电记录显示,高频电刺激PF使PD大鼠STN神经元自发放电减少,且该作用具有频率依赖性。另外,高频电刺激PF可使VM神经元兴奋,该作用也是频率依赖性的。我们在实验中同时观察到微电泳谷氨酸（glutamicacid,Glu）受体拮抗剂MK-801使STN神经元放电频率减少或完全抑制,微电泳t氨基丁酸（T-amino butyricacid,GABA）受体拮抗剂印防己毒素（picrotoxin,Pic）则使神经元放电频率增加。以上结果表明,GABA能和GIu能传入纤维可会聚于同-STN神经元,并对后者有紧张性作用。高频刺激PF,使该核团到STN神经元的Glu能兴奋性输出减少,导致STN的失活。这一作用通过基底神经节的间接通路,最终释放了丘脑运动核团VM的活性。高频刺激PF经PF,STN和VM的神经通路而改善PD大鼠神经行为。     

电刺激小脑顶核对主要心血管生理参数的影响

目的:本文通过研究电刺激小脑顶核对光电容积脉搏波的影响,探讨电刺激小脑顶核对于人体心血管系统产生的生理效应。方法:记录30位受试者在小脑顶核受刺激时的脉搏波数据,提取了上升支主波幅度H、上升沿斜率Slope、脉搏波波形特征量K值等5种波形特征值。对比分析在刺激中和刺激前后各特征值的变化并根据该变化描述电刺激小脑顶核所引起的生理变化。结果:电刺激小脑顶核使脉搏波呈现出灵敏的一过性变化。结论:特征值的变化反应出电刺激小脑顶核使外周血流量、外周阻力等生理参数发生了一过性的变化。     

Effect of electrodermal stimulation on single unit responses to acoustic stimulation in the parvocellular part of the medial geniculate body

The effect of electrodermal stimulation of the contralateral forelimb on responses arising in neurons of the parvocellular part of the medial geniculate body (MGB) to clicks was studied in cats anesthetized with thiopental and immobilized with myorelaxin (suxamethonium). Neurons whose responses to clicks were inhibited by electrodermal stimulation were located in zones of the parvocellular part of MGB adjacent to the posterior ventral nucleus and magnocellular part of MGB. Electrodermal stimulation had no effect on unit responses in more lateral zones of the parvocellular part. Intracellularly recorded responses of most neurons to clicks were of the EPSP-spike-IPSP or EPSP-IPSP type, whereas those to electrodermal stimulation were of the IPSP type only. Inhibition of responses under the influence of electrodermal stimulation could arise both in the presence and absence of an IPSP in the neuron. The mechanisms of the inhibitory effect of electrodermal stimulation on responses arising in neurons of the parvocellular part of MGB to stimulation by clicks are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 2, pp. 175–181, March–April, 1980.     

Sinusoidal galvanic stimulation of the labyrinths and postural responses

We studied the effect of sinusoidal stimulation of the labyrinths on postural reflexes in man, using a 0.3 Hz current of alternating polarity and +/- 1 mA intensity for stimulation. The test subjects were tested binaurally by the bipolar method (BB), with two electrodes on the mastoid processes, and binaurally by the monopolar method (BM), with electrodes localized bilaterally on the mastoid process and the hand. Stabilographic postural parameters were measured in 22 subjects in five experimental situations. Each situation lasted 60 s. Body sway, detected by astabilometer, was recorded on a Philips FM tape-recorder and then analysed off-line on a PDP-11/34 computer. On BB stimulation of the labyrinths, the variance of body sway in the left-right (LR) direction increased more than in the anteroposterior (AP) direction. In BM stimulation, only the variance of LR sway increased. Other posturographic parameters displayed a similar effect. From the aspect of body sway frequency, BB stimulation produced a peak in the course of the power spectral density of the lateral stabilogram at 0.3 Hz. In this experimental situation, a habituation effect was manifested, depending on the subject. It can be stated that binaural bipolar (BB) stimulation of the labyrinths selectively influences lateral body sway, while the increase in AP body sway in this situation is merely a concomitant phenomenon.