Effect of bacterial lypopolysaccharide on penicillin-induced seizure activity in rats

In experiments on Wistar rats, we found that, within an early period (2 to 4 h) after injection of bacterial lypopolysaccharide, LPS (0.1 mg/kg, i.p.), the latency of generalized seizures induced by injection of benzylpenicillin (sodium salt; 3.0 million IU/kg, i.p.) became significantly shorter, while the severity of seizure manifestations was higher than in the control group. Within this period, the power of oscillations of the delta and alpha-frequency ranges increased in the frontal cortex and hippocampal structures; fast ECoG components (beta and gamma rhythms) were suppressed, and the power of the theta activity decreased. In the hippocampal structures, these changes were more clearly pronounced, as compared with the neocortex. Within a later period of the action of LPS (12 to 18 h from the moment of injection), the latency of penicillin-induced seizures significantly exceeded the control value, and the severity of such seizures was lower. Under such conditions, we observed a smaller power of the synchronized activity of delta and alpha frequencies combined with intensification of the theta activity (most clearly pronounced in the hippocampal structures), and also an increase in the power of “desynchronized” rhythms (beta and gamma oscillations) in the cortex and hippocampus. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 236–241, May–June, 2008.     

Effect of repeated daily electrical stimulation on seizure activity in the rabbit limbic system

The order of appearance, the functional relations, and changes in the epileptiform effects of electrical stimulation of the limbic system (septum, amygdala, hippocampus) were studied. During repeated electrical stimulation regular changes took place in the seizure activity: the duration, frequency, and amplitude of the after-discharges were increased, their polarity was changed, seizures and unsynchronized high-amplitude activity appeared, and the after-discharges were reactivated. The most common variants of the seizure patterns are described. Close correlation was found between the greatest intensity of the after-discharges and the appearance of seizures. Besides a critical number of after-discharges, their parameters and their degree of irradiation also play an important role in the onset of the seizures. It is postulated that the limbic structures may play the role of an organized epileptogenic focus. Facts indicating that the seizure activity in response to direct electrical stimulation of the limbic structures may have a reflex mechanism are presented.     

Vagus nerve stimulation suppresses generalized seizure activity and seizure-triggered postictal cardiac rhythm changes in rats

In the present study, we investigated the effects of vagus nerve stimulation (VNS), a proposed treatment for patients with intractable epilepsy, on cardiac rhythm following seizures induced by pentylenetetrazole (PTZ) in Wistar rats. After a baseline recording of electroencephalogram (EEG), electrocardiogram (ECG) and blood pressure (BP), rats in the first group received a single convulsive dose of PTZ (70 mg/kg) (Group 1). In the other two groups, the Wistar rats were implanted with a cuff electrode on the left cervical vagus nerve. One day after surgery, rats in the second group were treated with VNS (Group 2), whereas rats in the third group were connected to the stimulator but did not receive VNS (Group 3). Ten minutes after VNS onset, 70 mg/kg dose of PTZ was injected. EEG, ECG and BP were continuously recorded during post-injection period. Seizure severity was scored behaviorally. Then, baseline, ictal and postictal periods were analyzed for cardiac rhythms, seizure severity and blood pressure variability. PTZ treatment induced tonic-clonic seizure activity in all animals of Group 1 and Group 3. In these groups a marked increase of mean arterial blood pressure (MABP) but a significant decrease in heart rate and PP interval fluctuations was observed at postictal period. However, in the VNS-treated group the seizure scores and cardiac parameter returned to the baseline level. Present results emphasize that VNS effectively reduces seizure severity and suppress the seizure-induced cardiac rhythm changes.     

Effect of diazepam on electrical activity and Na,K-ATP-ase level in a penicillin-induced epileptic focus in the rat cerebral cortex

Application of penicillin solution to the motor cortex in rats evoked the appearance of interictal discharges and epileptic seizures. After administration of diazepam in a dose of 2 mg/kg, Na,K-ATPase activity in the unpurified synaptosomes fraction of the cortex in the zone of the focus was increased by practically 100% compared with the level of activity of the enzyme in the focus without diazepam. Interictal discharges and epileptic seizures underwent different changes following intramuscular injection of diazepam. The frequency and variability of amplitude of the interictal discharges increased after administration of diazepam, whereas epileptic seizures were depressed. This effect was potentiated with an increase in the dose of diazepam. It is suggested that the opposite action of diazepam on epileptic seizures and interictal discharges may be evidence that the mechanisms lying at the basis of the development of these phenomena are different.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 349–357, July–August, 1980.     

Effect of transcranial electrical stimulation on sleep in rats

Transcranial electrical stimulation with high frequency intermittent current (Limoge's current) was delivered to normal rats and to PCPA-treated rats with impaired sleep. Electrocorticogram was continuously recorded for quantifying the stage of the sleep-waking cycle. The current did not affect the sleep pattern of normal rats whereas the number of paradoxical sleep episodes increased in insomniac animals. The increased duration of paradoxical sleep in PCPA-treated rats favored the recovery of sleep in this group. The stimulation increased the brain serotonin turnover, which could possibly contribute to its hypnogenic action.     

Effects of PN 200-110 on penicillin-induced epileptic activity in the cerebral cortex of rats]

In experiments on freely moving Wistar rats it was shown that an intraperitoneal administration of PN 200-110 in a dose of 2 mg/kg in the period of steady epileptic activity (EpA) with regular generation of ictal discharges in penicillin--induced focus resulted in suppression of EpA in most animals. Antiepileptic effect of the drug was manifested by decreasing frequency appearance of ictal discharges and shortening of the epileptic focus existence time. Intraperitoneal administration (5 mg/kg) and intraventricular injection (10 nmol) of PN 200-110 20 min before the epileptic focus formation resulted in an increased latency period of appearance interictal discharges and decreased number of ictal discharges, and shortening of the existence time of epileptic focus.     

Effects of magnesium and nickel ions on penicillin-induced focal epileptic activity in the cerebral cortex of rats]

In experiments on freely moving male Wistar rats on the model of penicillin-induced focal epileptic activity (EA) (the application onto the sensorimotor cortex of a filter paper soaked with benzylpenicillin sodium salt solution) it was shown that addition of MgSO4 (series 1) and NiCl2 (series 2) into the solution of penicillin significantly weakened EA. The combination of Mg2+ and Ni2+ with penicillin (series 3) produced a more significant suppression of EA as compared with separate application of the above-mentioned ions: the latency period of appearance of interictal discharges (IID) increased, the frequency and amplitude of IID decreased much more, no ictal discharges appeared in any animal, the duration of epileptic foci reduced to a much greater extent. This effect can be explained by the blockade of Ca current by the above-mentioned ions. One can suppose that the amplification of antiepileptic effects of combined action of Mg2+ and Ni2+ was due to an increase in the number of blocked voltage-dependent and NMDA-operated calcium channels.     

Effect of delta sleep-inducing peptide, anticonvulsant preparations and nicotinamide on generalized seizure activity

The influence of delta-sleep inducing peptide (DSIP) upon seizures induced by corazol, bicuculline, picrotoxin, strychnine, thiosemicarbazide were investigated in experiments on F1(CBA X C57 BL/6) mice. It was shown that DSIP increased the latency of first seizure manifestation which were induced by corazol, bicuculline and picrotoxin and also resulted in a suppression of seizure severity of corazol and bicuculline induced seizures. Anticonvulsant action of DSIP was evident under the condition of the mild severity seizures development. The effect of DSIP was mostly pronounced in range of its doses from 10 to 100 mcg/kg. DSIP when combined with phenobarbital, carbamazepine, diphenylhydantoin or nicotinamide enhanced the antiepileptic effects of these anticonvulsant drugs.     

Effect of nicotinamide on focal and generalized epileptic activity in the cerebral cortex

Intraperitoneal injection of nicotinamide to rats inhibits epileptic activity induced by penicillin application in the animals' brain cortex. It has been found in experimental primary-generalized epileptic activity induced by bemegride that preliminary injection of nicotinamide increased the latency of the emergence of the first epileptic seizures. Addition of nicotinamide to synaptosomal suspension inhibited accumulation in it of the products of lipid peroxidation. Relationship between antioxidant properties of nicotinamide and its antiepileptic activity is discussed.     

Effect of artemether on pentobarbitone sleep and electrical activity in rats

Artemether (AM), a highly effective treatment for multidrug-resistant malaria and a component of artemisinin combination therapy, has been associated with some neurotoxicity following repeated high doses. This study was aimed at investigating the effect of AM on pentobarbitone sleep and electrical activities in rats. Wistar rats received AM i.p. at 3 dose levels: 1.5, 7.5, and 15 mg/kg, whereas control rats received 0.2 mL of the vehicle (3% v/v Tween 80). AM administered 20 min before pentobarbitone had no significant effect on the onset and duration of sleep. However, after a 7-day pretreatment, AM dose-dependently prolonged pentobarbitone sleep, as did chloramphenicol. Electroencephalogram and electromyogram recordings 20 min after pretreatment showed that AM (15 mg/kg) exhibited inhibitory activity similar to chlorpromazine as opposed to the excitatory effect of amphetamine. When pretreated for 7 days, rats receiving 1.5 mg/kg AM also showed inhibitory activity of the cortical centres, whereas desynchronization of the optic tectum and reticular formation was observed in rats pretreated with 7.5 and 15 mg/kg AM. The present data suggest that although the therapeutic equivalent dose of 1.5 mg/kg AM had no appreciable effects on pentobarbitone sleep but caused reduced electrical activity in rats, higher doses have more profound effects on both indices.     

Effect of peripheral stimulation on neocortical electrical activity in the chronic premesencephalic cat

Chronic experiments on 19 adult cats showed that on the second or third day after premesencephalic section through the brain stem preserving the lemniscal pathways, auditory, olfactory, and cutaneous stimulation evoke diffuse neocortical activation. Although photic stimulation evoked responses in the visual cortex, it could not desynchronize the neocortical activity. It is postulated that diffuse neocortical activation in cats with a complete block of the mesencephalic recticular formation in response to auditory, olfactory, and cutaneous stimulation arises through excitation of the posterior hypothalamus.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 7, No. 5, pp. 493–499, September–October, 1975.     

Effects of applying electrical stimulation to the locus coeruleus on neuronal activity in the parietal association cortex

It was shown during experiments on cats undergoing surgery under ketamine-induced anesthesia and immobilized with myorelaxin that applying trains of stimuli to the locus coeruleus (LC) produces an effect on 79% of parietal cortex neurons. This manifests as inhibition lasting 300–700 msec or a 16–32% decline in the activity rate of neurons with background activity. Hyperpolarization of 5–7 mV lasting 120–500 msec preceded by a latency of 30–90 msec was noted in such neurons as well as "silent" cells during intracellular recording. Duration of the inhibitory pause in neuronal background activity induced by transcallosal stimulation (TCS) increased by 50–200 msec under the effects of conditioned stimuli applied to the LC. Duration of the IPSP triggered by TCS likewise increased (by 50–100 msec) under the effects of LC stimulation. It was concluded that the effects of stimulating the LC on neuronal activity in the parietal cortex may manifest either directly, as inhibition of background activity and hyperpolarization, or else as modulation of influences exerted by other neurotransmitters.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 4, pp. 486–494, July–August, 1990.     

Effect of serotonin on the electrical activity of the cerebral cortex in the rabbit

Application of serotonin on the rabbit cerebral cortex produced prolonged (minutes) periodical oscillations of the activation level and the level of spatial synchronization of neocortical biopotentials. Periodical changes of biopotentials correlation were due above all to a significant reorganization of phasic correlation of the EEG theta-components of remote neocortex points. The changes may be explained by the appearance, due to serotonin, of slow oscillations of the excitation level of the cortical neurones, as a systemic transitional reaction to the change in the balance of excitatory and inhibitory processes. The ability of serotonin to influence phasic relationships of the distantly-synchronous cortical theta-rhythm is of considerable significance for conditioned activity.     

Effect of neuromuscular electrical stimulation on motor cortex excitability upon release of tonic muscle contraction

The aim of the present study was to investigate the neurophysiological triggers underlying muscle relaxation from the contracted state, and to examine the mechanisms involved in this process and their subsequent modification by neuromuscular electrical stimulation (NMES). Single-pulse transcranial magnetic stimulation (TMS) was used to produce motor-evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) in 23 healthy participants, wherein motor cortex excitability was examined at the onset of voluntary muscle relaxation following a period of voluntary tonic muscle contraction. In addition, the effects of afferent input on motor cortex excitability, as produced by NMES during muscle contraction, were examined. In particular, two NMES intensities were used for analysis: 1.2 times the sensory threshold and 1.2 times the motor threshold (MT). Participants were directed to execute constant wrist extensions and to release muscle contraction in response to an auditory “GO” signal. MEPs were recorded from the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles, and TMS was applied at three different time intervals (30, 60, and 90?ms) after the “GO” signal. Motor cortex excitability was greater during voluntary ECR and FCR relaxation using high-intensity NMES, and relaxation time was decreased. Each parameter differed significantly between 30 and 60?ms. Moreover, in both muscles, SICI was larger in the presence than in the absence of NMES. Therefore, the present findings suggest that terminating a muscle contraction triggers transient neurophysiological mechanisms that facilitate the NMES-induced modulation of cortical motor excitability in the period prior to muscle relaxation. High-intensity NMES might facilitate motor cortical excitability as a function of increased inhibitory intracortical activity, and therefore serve as a transient trigger for the relaxation of prime mover muscles in a therapeutic context.     

跨颅电刺激对大鼠抑郁症的治疗作用

目的：探讨跨颅电刺激对大鼠抑郁症的治疗作用。方法：跨颅电刺激抑郁症大鼠左侧前额叶皮层,敞箱实验测定大鼠行为学变化,荧光法测定单胺类递质含量的变化。结果：跨颅直流电和低频脉冲电刺激后,大鼠敞箱实验中垂直和水平运动得分均较模型组显著升高（P〈0.05）;且大鼠左侧前额叶皮层和海马5-HT、NE含量较模型组显著升高（P〈0.05）,而前额叶皮层DA含量无显著变化（P〉0.05）。结论：直流电和低频脉冲电跨颅刺激左侧前额叶皮层,对抑郁症均有显著治疗作用。     

Optical recording of activity in the hamster gustatory cortex elicited by electrical stimulation of the tongue

Voltage sensitive dyes in conjunction with a photodiode arraywere used to make multi-site optical recordings in the hamstergustatory cortex. Two discrete, but adjacent, areas of thiscortex were activated when different parts of the tongue wereelectrically stimulated. These two areas were activated withdifferent latencies suggesting a temporal as well as a spatialmapping of the periphery onto the cortex.