Effect of aminazin on changes in the electrical activity of the cerebral cortex under the influence of the toxin C1. perfringens type A]

Experiments on cats revealed that injection of chlorpromazine (3 mg/kg of body weight, intramuscular) one hour prior to the Cl. perfingens toxin type A injection prevented the appearance of desynchronization of the electrical activity of the cerebral cortex usually observed during the first phase of intoxication. Chlorpromazine injection postpones the appearance of the electrical activity depression phase during the second phase and prolonged the animals' life span from 1.5 to 2 times. The effect of chlorpromazine was apparently connected with the block of the adrenergic structures of the brain stem reticular formation.     

Changes in the electrical activity of the cerebral cortex under the combined influence of Cl. perfringens type A toxin and products of Cl. butyricum activity]

A study of the changes of the electrocorticogram (ECoG) and the electrocardiogram (ECG) in combined action of Cl. perfringens, type A, and of the Cl. butyricum broth culture filtrate showed that desynchronization of the cortical electrical activity and its subsequent depression occurred at earlier periods than in the case of isolated administration of Cl. perfringens toxin. The general character of the changes in the cortical rhythmic activity remained the same as in intoxication caused by Cl. butyricum toxin alone. The ECoG and ECG changes occurred at shorter intervals. Cl. butyricum filtrates induced no ECoG and ECG changes. It is supposed that the effect of the products of the Cl. butyricum vital activity consisted in increase in the tissue barrier permeability and, in this connection, in a greater penetration of Cl. perfringens toxin into the tissues, including the central nervous system.     

Interhemispheric relationships of electrical activity in the blinking dominant in rabbits

The study of intercentral and interhemispheric relations of the electrical activity of the cerebral cortex during formation and functioning of winking dominant, by the method of spectral-correlation analysis, has shown that the dominant focus is characterized by an increase of spectrum power in the range of delta-frequencies and a raise of coherence level of potentials in the same range that leads to the appearance of interhemispheric asymmetry according to these parameters. Appearance of the dominant state in the opposite hemisphere is accompanied by a reconstruction of the electrical activity characteristic of dominant focus.     

Influence of certain stimulation parameters on the character of the cortical self-sustained after-discharge

The ECoG pattern of self-sustained after-discharges (SSADs) evoked by rhythmic electrical stimulation of the cerebral cortex is far from uniform. In acute experiments on male rats the authors studied the significance of the frequency, intensity and length of stimulation for the character of the resultant SSAD. In the first group (11 rats), a stimulation frequency of 8 Hz was used; the stimulation series, which lasted 10 and 20 s, always led to the formation of a SSAD composed of spike-and-wave rhythm right from the outset. Shortening the time of stimulation markedly reduced its effectiveness. In the second group (10 animals), stimulation with 50 Hz frequency often evoked a complex SSAD starting with desynchronization, which was followed by fast spike activity of increasing amplitude and only later by spike-and-wave rhythm or by polyspike-and-wave rhythm. Towards the end, serrated waves--i.e. graphoelements typical of SSADs evoked by electrical stimulation of limbic structures--often appeared in the SSAD. A higher stimulation intensity increased the incidence of this complex SSAD. In this group a minimum duration of stimulation was also essential (series of less than 2 s were not reliably effective). When this second type of SSAD ended, depression of ECoG activity was followed in 27% of the cases by a spontaneous recurrent seizure (RS). The ECoG character of these RS can be very variable. The two types of seizures evoked by slow and fast stimulation differ from each other not only in respect of their ECoG pattern (where the difference is probably due to more pronounced propagation to subcortical structures after faster stimulation), but also as regards the presumed mechanism of their onset.     

Circadian rhythms of DNA content in brain and kidney: effects of environmental stimulation

Male adult Wistar rats kept under natural lighting show circadian rhythms of DNA content and DNA synthesis in the cerebral cortex, cerebellum and kidney. In the cerebral cortex the acrophases of the 2 rhythms almost coincide during the dark period. On the other hand, in kidney, the acrophase of DNA synthesis is phase-advanced by about 14 h with respect to the acrophase of DNA content, which occurs in the dark span, as in the cerebral cortex. Comparable results were obtained in 5 week-old rats raised under artificial lighting conditions (LD 7:19) and exposed for a few days to sensory and social stimulation (an enriched sensory environment). At variance with the latter data, the circadian changes of DNA content and synthesis flattened out and were not statistically significant in the cerebral cortex of 5 week-old rats kept for a few days under conditions of sensory and social deprivation (an impoverished sensory environment). A similar effect occurred in kidney with regard to the rhythm of DNA content, while the circadian rhythm of DNA synthesis remained statistically significant but was phase-delayed by about 6h with respect to the corresponding rhythm occurring in the enriched environment. In sensory impoverished rats, MESOR values of kidney wet weight and DNA specific activity were significantly higher than in sensory enriched rats, while MESOR values of DNA content were significantly lower. The data demonstrate the striking dependence of the circadian variations of DNA content and synthesis on the nature of environmental stimulation.     

Changes in the oxygen tension level in different brain structures of rats in the waking-sleep cycle

Changes of oxygen tension level (pO2) in the visual cortex, dorsal hippocampus, lateral hypothalamus and central grey substance were studied during wake-sleep cycle in rats. The dependence was established of pO2 level changes on the character of behavioural reactions and on the accompanying hippocampal EEG activity: during orienting-investigatory and active defensive behaviour and also during paradoxical sleep, accompanied by hippocampal theta rhythm, pO2 level increased; during passive-defensive behaviour "freezing" reaction accompanied by desynchronization of the hippocampal rhythmic, the level of pO2 decreased. The obtained data confirm Routtenberg hypothesis about two relatively independent systems of ascending activation with different types of hippocampal EEG activity and supplement it with a thesis that the activity of these systems is accompanied by different shifts of brain oxidative metabolism.     

Disordered cardiac electrical stability in beta-adrenergic damage and antioxidant protection]

The electrical threshold of ventricular fibrillation induced by premature single impulses and the ectopic activity and also an abnormal conduction during vagus inhibition of sinus node were estimated 24 hours after the administration of isoproterenol (10 mg/kg, s/c, on time) in rats. In addition the cardiac contractile function of the left ventricle was studied. The study was performed on male Wistar rats, 250-300 body weight, under nembutal anesthesia. Isoproterenol had no effect on the contractile function in the rest and during maximal isometric load, induced by coarctation of ascending aorta. But in the treated animals the threshold of fibrillation fell more than 2-fold and the vagal bradycardia was more 2-fold then in the untreated animals. The AB-block, idioventricular rhythm and extrasystoles appeared during vagal bradycardia in treated animals, while in the untreated ones there were no any disturbances. The preliminary administration of the antioxidant ionol (BMT, 30 mg/kg, per os, in sun oil) prevented the enumerated shifts.     

Investigation of the functional role of the septum

A spectral-correlation analysis was made of the EEG recorded from the motor and visual cortex, hippocampus, and septum (in some series of experiments, the lateral geniculate body and mesencephalic reticular formation also) of rabbits in the presence or absence (background) of sensory stimulation. To investigate the functional role of the septum as a pacemaker the method of "rhythm binding" by electrical stimulation of the septum (lateral and medial nuclei) was used. By electrical stimulation of the medial nucleus of the septum at a frequency of 4–30 Hz rhythm binding was successfully obtained in all regions studied. Maximal rhythm binding was observed in cortical potentials. It is postulated that cortical rhythmic activity is generated as a result of physiological interaction between cortex and septum.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 267–275, May–June, 1976.     

Cerebral hemodynamic reaction to physical exercise of moderate intensity

The aim of this research was to study the cerebral hemodynamic reaction to stepped increase of physical exercises during the bicycle ergometer test in 12 young healthy male patients. The starting value of exercise was 0.25 W/kg of the body weight, with the 0.25 W/kg increase at every subsequent step up to the value of 1.75 W/kg of the body weight. Hemodynamic parameters were registered with the Doppler ultrasonography of middle cerebral artery before the study, during the last 10 seconds of every step, and during the 3 minutes of restorative period with a 1-minute interval. The peak systolic blood flow increase in the middle cerebral artery was observed only as the result of low intensity exercises (0.25 W/kg of the body weight). The blood pressure (BP) restoration occurred by the end of the third minute of the rest, while the cerebral hemodynamic indices became normal during the first minute. The research revealed a correlation between increases of vascular resistance caused by physical exercises and the BP, and no correlation between increases of peak systolic blood flow and BP, which displays the phenomenon of cerebral circulation autoregulation.     

Effect of tetanus toxin and colchicine on synaptic membranes of rat cerebral cortex]

It was shown that purified tetanus toxin did not influence the activity of the Na, K-ATP-ase fractions of the synaptic membranes of the rat cerebral cortex, it had no effect on the inhibition of Na, K,-ATP-ase under electrical stimulation of the synaptic membrane suspension, or the GABA--3H binding by the synaptosomes in vitro. Tetanus toxin (400--4000 DLM) and colchicine (1 mM) induced a decrease of osmotic sensitivity of the nerve endings. Colchicine in low concentrations (10(-5)-10(-3) M) failed to influence Mg-and Na, K-ATP-ases, but considerably inhibited both ATP-ases at higher concentrations.     

Tetanus toxin effect on the metabolism and release of acetylcholine in rat central nervous system

The effect of tetanus toxin in doses of 30 mcg/kg on the content, synthesis and release of acetylcholine, and on the activity of choline acetylase and acetylcholine esterase in the central nervous system of the rat was studied. The investigations were carried out after the appearance of tetanus. We found that the tetanus toxin: a) caused no changes in the acetylcholine content in the cerebral cortex and brain stem, and also in the cervical and lumbar parts of the spinal cord; b) stimulated acetylcholine synthesis in the brain stem and in the cervical and lumbar parts of the spinal cord but not in the cerebral cortex; c) activated choline acetylase; d) had no effect on acetylcholine esterase activity; e) released acetylcholine from the neurons in the brain stem and spinal cord. The release could not be inhibited by low concentration of potassium ions in the medium or increased with electrical stimulation.     

Some aspects of neurophysiological basis of insecticide action.

When the insecticide parathion was administered to awake, unrestrained rats with chronically implanted brain electrodes, it was observed that the latency of the averaged flash-evoked potential in the visual cortex and superior colliculus was increased and the amplitude was decreased 2 to 4 hours later with responses returning to pretreatment levels about 8 hours after administration. Similarly, after administration of several dose levels of parathion in the rat, durations of phases of the maximal electroshock seizure (MES) pattern were altered to the greatest extent 4 hours later, but effects disappeared at 24 hours. These effects of parathion on the MES and evoked potentials coincided with a fall in blood and brain acetylcholinesterase (AChe) activities but disappeared after AChe inhibition had reached its peak and stabilized. Brain AChe activities required 2 to 4 weeks for recovery whereas blood AChe activity recovered in 1 week following inhibition by parathion (at least 2 mg/kg body weight). Studies in the monkey demonstrated similar results. Because these measurements of central nervous system function returned to normal despite continued inhibition of AChe activity, the results are interpreted to mean either that adaptation of evoked potentials or MES responses to prolonged AChe inhibition can occur in the rat and monkey after parathion administration or that some of the effects of parathion do not depend on AChe inhibition. Administration of DDT (100 mg/kg by mouth) to awake, unrestrained rats markedly increased the amplitude of spontaneous electrical activity in the cerebellum, whereas there was much less effect on electrical activity recorded simultaneously in the occipital cortex, reticular formation, and medial geniculate body. Similarly, DDT administration had marked effects on the averaged, sound evoked potential recorded in the cerebellum; DDT caused the appearance and increased the amplitude of an early component of this response not usually present during control recordings. Sound-evoked potentials recorded simultaneously from the frontal and occipital cortex and reticular formation were affected less or were decreased in amplitude by administration of DDT.     

The herbal medicine Toki-shakuyaku-san improves the hypertension and intrauterine growth retardation in preeclampsia rats induced by Nomega-nitro-L-arginine methyl ester.

The chronic inhibition of nitric oxide (NO) synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME) induces a preeclampsia-like syndrome including hypertension and intrauterine growth retardation (IUGR) in pregnant rats. We tested the traditional herbal medicine Toki-shakuyaku-san (TS) for beneficial effects in this model. L-NAME was infused subcutaneously into pregnant rats from day 14 of gestation. TS (1 g/kg, 2 g/kg) was administered by gavage from day 14 to 20. Systolic blood pressure was measured on day 19. On day 20, rats were sacrificed and serum NO levels, placental weight, fetal body weight, fetal cerebrum weight and the thickness of the cerebral cortex were analyzed. TS (1 g/kg, 2 g/kg) inhibited L-NAME-induced hypertension. The decrease in fetal body weight, cerebrum weight and thickness of the cerebral cortex was abrogated by TS (2 g/kg). The effect of TS on blood pressure was found only in the rats that were both pregnant and infused with L-NAME. L-arginine, at the amount equivalent to that contained in TS, showed no effect. Further, the change in serum NO levels induced by TS was only marginal. TS thus improved the hypertension and IUGR in preeclampsia rats induced by L-NAME in a NO-independent manner. These data suggested that TS may be beneficial for the treatment and prevention of preeclampsia.     

The motor dominant in man]

Study of the motor dominant in man has shown that in aftereffect of rhythmic electrocutaneous stimulation of hand, a latent focus of excitation is formed in the CNS. When using sensory stimuli (light, sound) and also stimuli, addressed to the second signal system, a hand motor reaction appears in the rhythm of earlier electrocutaneous stimulation, what testifies to preservation of rhythmic nature of excitation in the dominant focus. Summation process in the dominant focus is not reflected in human consciousness. Study of the brain biopotentials has shown that at formation of human motor dominant, typical changes of spectral-coherent characteristics of the neocortex electrical activity appear: within the "dominant" hemisphere, the spectrum power, increases in the range of low frequencies; highly coherent connections of electrical processes appear in the delta-range of the frontal-parietal area at conjugate decrease of combination of processes in the parietal-occipital area of the cerebral cortex. Formation of the dominant focus in one hemisphere causes general reconstruction of the structure of intercentral relations of both hemispheres electrical activity.     

Internal desynchronization of the circadian activity and feeding rhythm in an owl monkey (Aotus lemurinus griseimembra): a case study

In the free-running circadian locomotor activity rhythm of a 7-year-old male owl monkey (Aotus lemurinus griseimembra) kept under constant light and climatic conditions (LL 0.2 lux, 25°C ± 1°C, 60 ± 5% relative humidity [RH]), a second rhythm component developed that showed strong relative coordination with the free-running activity rhythm of 24.4h and a 24h rhythm. The simultaneously recorded feeding activity rhythm strongly resembled this rhythm component. Therefore, it seems justified to infer that there was an internal desynchronization between the two behavioral rhythms or their circadian pacemakers, that is, between the light-entrainable oscillator located in the suprachiasmatic nuclei (SCN) and a food-entrainable oscillator located outside the SCN. This internal desynchronization may have been induced and/or maintained by a zeitgeber effect of the (irregular) 24h feeding schedule on the food-entrainable oscillator. The weak relative coordination shown by the activity rhythm indicates a much weaker coupling of the light-entrainable oscillator to the food-entrainable oscillator than vice versa. (Chronobiology International, 17(2), 147-153, 2000)     

CNS depressive role of aqueous extract of Spinacia oleracea L. leaves in adult male albino rats

Treatment with Spinacia oleracea extract (SO; 400 mg/kg body weight) decreased the locomotor activity, grip strength, increased pentobarbitone induced sleeping time and also markedly altered pentylenetetrazole induced seizure status in Holtzman strain adult male albino rats. SO increased serotonin level and decreased both norepinephrine and dopamine levels in cerebral cortex, cerebellum, caudate nucleus, midbrain and pons and medulla. Result suggests that SO exerts its CNS depressive effect in PTZ induced seizure by modulating the monoamines in different brain areas.     

Stimulation of Fructose-1,6-Biphosphatase Activity and Synthesis in the Cerebral Cortex of Rats Submitted to the Convulsant Methionine Sulfoximine

Purification of rat cerebral cortex fructose-1,6-biphosphatase (FBPase) was performed by substrate elution from phosphocellulose, followed by Sephadex G-200 column filtration. The purified enzyme exhibited an optimum at pH 7.5, and its catalytic properties were very similar to those of the purified whole-brain enzyme previously prepared by Majumder and Eisenberg in 1977. The isolated preparation was electrophoretically homogeneous. The molecular weight of the enzyme subunit was 40,000; the hydrophobic amino acids predominated with 592 residues, and tryptophan was not detected. Expressed as mumol fructose-1,6-biphosphate hydrolysed per g brain tissue wet weight per min, FBPase activity increased twofold 24 h after an intraperitoneal injection of 100 mg per kg body weight of the convulsant methionine sulfoximine (MSO); the increase of the rate of incorporation of [1-14C]valine into brain FBPase was 2.8-fold under the same experimental conditions. A rabbit specific antiserum against rat cerebral cortex FBPase was prepared, and immunotitration studies confirmed both an increase in the number of molecules and the activation of brain FBPase, 24 h after administration of MSO. The increase of the number of brain FBPase molecules, induced by MSO, was due to an increase in synthesis of the enzyme, as shown by a double-label valine incorporation study.     

Vagal afferents and EEG rhythms in the Sl area in anesthetized cats: similarities between responses to electrical and chemical (phenyldiguanide) stimulations

In anesthetized, artificially ventilated cats with open chest, bilateral stimulation of all afferent vagal fibres (pulse duration: 800 microseconds, 30 Hz, train duration 30 to 40 s) produced marked changes in the spontaneous EEG activities in the primary somatosensory cortex (Sl area). They were characterized by depressed background rhythms, with a tendency to desynchronization, decreased amplitude and number of spindles, with altered pattern, and/or evoked sustained fast rhythmic activities. These effects occurred within 1 to 5 sec during vagal stimulation. On the contrary, the EEG response was weaker or absent when only myelinated vagal afferents were stimulated (100 microseconds). I.v. injection of phenyldiguanide (PDG), used for stimulation of unmyelinated vagal sensory fibres and mainly of pulmonary afferents, induced EEG changes within the first 30 s, similar to those observed during electrical vagal stimulation. These EEG responses were unrelated to the induced hypotension. Cervical bivagotomy produced persistent changes in EEG activity, with enhancement of the magnitude, duration and number of spindles, which resembled the delayed effects induced by PDG. The present results obtained with three test agents (electrical or chemical vagal stimulation and bivagotomy) demonstrated that, in cats, vagal afferent information interacted with the spontaneous EEG rhythms in the Sl area.     

Mechanism of action of naphthylvinylpyridine]

Naphthylvinylpyridine (NVP) in the cat cerebral cortex (50 mg/kg) and in the mouse brain (100 and 250 mg kg) caused inhibition of choline acetyltransferase (ChA) and didn't influence the acetyl- and butyrilcholinesterase activity and acetylcholine (Ach) content in the mouse brain. NVP (25 mg/kg) failed to influence the ChA activity. Pretreatment with NVP (25 and 250 mg/kg) increased the duration of hexenal sleep in mice greatly, and a dose of 250 mg/kg (but not of 25 mg/kg) enhanced the atropine activity in mice poisoned with armine. NVP (250 mg/kg) reduced the release of Ach from the cerebral cortex of a cat, spontaneous and evoked by atropine and electrical stimulation of the reticular formation of the brain stem. A conclusion was drawn that the pharmacological effect of NVP when the latter was applied in combination with atropine and armine could be connected with the anti-Cha action and the inhibition of the newly-formed Ach, rather than with depression of the microsomal enzymes.     

A spectral-correlational analysis of the EEG of the neocortex in the rabbit in a state of thirst

Summate electrical activity of the rabbit neocortex during formation of drinking excitation was studied by means of mathematical analysis. It is shown that the change of the electrical activity depends on the level of drinking excitability created by various duration of water deprivation (24-48 h) and is expressed in a generalized lowering of potentials amplitude without frequency change. Spectro-correlative EEG analysis showed that lowering of spectrum power took place within the whole analyzed frequencies range. Besides, an increase took place of interconnections of the cortical electrical processes, estimated by coherence function. It may by suggested that the manifested reconstruction of spectro-correlative characteristics of the neocortical biopotentials reflects a formation of motivational excitation establishing optimal level of cortex functioning.