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PubMed1991

Reversal of apnoea by aspiration reflex in anaesthetized cats.

Various flow and timing characteristics of breathing as well as electrocorticographic (ECoG) records were analysed in a model of reversible respiratory failure induced by N2 inhalation in 27 anaesthetized cats. During the first minute of respiratory arrest, nasopharyngeal stimulation by an elastic nylon fibre elicited a typical sniff- or gasp-like aspiration reflex (in 88.8% of cases), whilst similar tracheobronchial irritation evoked a weak cough reaction in one third of cases (34.2%). The aspiration reflex could also be evoked in progressive stages of apnoea characterized by very low and even isoelectric ECoG activity immediately before imminent irreversible respiratory failure, and it could interrupt and replace the periodic gasping sometimes occurring during apnoea. The reflex, comprising powerful inspiration efforts, could be evoked during apnoea many times in succession. Repeated aspiration reflexes alone resulted in recovery from hypoxic apnoea with gradual normalization of ECoG and subsequent restitution of spontaneous breathing even more frequently than it occurred in periodic gasping. Successful resuscitation from hypoxic apnoea by the aspiration reflex in cats suggests that nasopharyngeal stimulation can affect the mechanisms underlying the failure and restitution of breathing at least in some forms of apnoea.

Animals↗

PubMed1991

Behavioural, electrocortical spectrum power and body temperature changes after microinfusion of some lymphokines in the rat brain.

Interleukin-1, interleukin-2 and interleukin-3 injected into the third cerebral ventricle produce typical behavioural sedation and/or sleep and ECoG synchronization in rats. Much smaller doses were required to produce similar behavioural and ECoG spectrum power effects after infusion of interleukins into the locus coeruleus. Interleukin-1 and interleukin-3 induced pyrogenic effects while interleukin-2 produced no pyrogenic actions. These effects were blocked by specific anti-interleukin receptors monoclonal antibodies. In addition, naloxone was able to antagonize the central effects of IL-2 but it did not affect the typical changes induced by IL-1. These results are consistent with the hypothesis that the behavioural, body temperature and ECoG changes of these lymphokines are mediated by specific receptors.

Animals↗

PubMed1976

[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.

Animals↗

PubMed1990

Anticonvulsive activity of a barbiturate derivative HB-7 in a model of allylglycine-induced epilepsy in cats.

With the aim of characterizing further the anticonvulsive activity of the newly-synthesized barbituric derivative 2-hydroxylamino-5-ethyl-5-sec. penthylbarbituric acid (HB-7), we studied its effects on allylglycine-induced epileptiform electrocorticogram (ECoG) in cats under acute conditions. Pentobarbital (PB) was used for comparison. Allylglycine (AG) was administered in a dose of 100 mg/kg i.v. to all cats. The control animals were treated with AG only. HB-7 and PB were applied in doses of 20 mg/kg i.p., about 60 min after AG. Intermittent light stimulation (ILS) at flash rate of 8/s and 25/s was applied to some animals. The ILS-stimulated animals were also divided in three groups: controls and animals treated with HB-7 or PB in the same dose. AG led to the appearance of paroxysmal ECoG activity: single and multiple spikes and spike-waves appeared first, to be followed later by generalized seizure activity. No AG-induced convulsions appeared in the cats treated with HB-7, but the AG-induced spikes and spike-waves remained unchanged. The effect of PB on the AG-induced paroxysmal ECoG activity was similar to that of HB-7, but the addition of PB provoked the appearance of slow waves and spindles, mixed with spikes and spike-waves. Although the paroxysmal character of the activity was more pronounced in the ILS-stimulated animals than in the group without ILS, HB-7 and PB (albeit to a lesser extent) inhibited the AG-induced discharges.(ABSTRACT TRUNCATED AT 250 WORDS)

Allylglycine↗

PubMedDate not supplied

Electrocorticographical observation of seizures induced by pentylenetetrazol (PTZ) injection in rats.

The various seizure responses observed behaviorally in freely moving rats after repeated pentylenetetrazol (PTZ) injections were compared with simultaneous electrocorticographical (ECoG) recordings. Seizures induced were divided into 7 behavioral categories (grade 0-6): grade 0, no behavioral seizures; grade 1, head nodding, head twitching; grade 2, myoclonic jerks; grade 3, head twisting, forelimb clonic convulsions; grade 4, kangaroo position; grade 5, falling down; grade 6, tonic convulsions. Specific behavioral seizure types were always associated with identifiable ECoG patterns. All rats which exhibited higher than grade 3 seizures developed decrease in spontaneous movements and decreased amplitude in ECoG activity after the end of their behavioral seizures, which suggests the existence of post-ictal inhibition. Both myoclonic jerks (grade 2) and tonic convulsions (grade 6) are important features of these seizure types which are not seen in electrical amygdaloid seizure models. This seizure classification will be useful for further rat PTZ seizure studies.

Animals↗

PubMed1990

The effects of brain-stem section on the breathing and behavioural response to morphine in the fetal sheep.

In the unanesthetized fetal sheep the administration of morphine causes initial apnoea followed by hyperpnoea. We thought that a section of the brain at midcollicular level might separate these two effects. Therefore we sectioned the brain stem of five fetuses at 132 +/- 1 (SEM) days of gestation and compared their responses to morphine (17 experiments) with that observed in seven intact fetuses at similar gestational ages (15 experiments). Brain stem sections were confirmed morphologically and histologically. Morphine, 1 mg/kg was injected in the fetal jugular vein during low-voltage electrocortical activity (ECoG). We measured ECoG, eye movements, diaphragmatic activity, blood pressure and amniotic pressure. Sectioned fetuses before the administration of morphine had a complete dissociation between ECoG and breathing activity. With the administration of morphine we found: (i) the length of the apnoea was 139.8 +/- 15.5 min in sectioned fetuses and 17.0 +/- 5.8 min in intact fetuses (P less than 0.01); and (ii) there was no hyperpneic response in the sectioned fetus whereas the length of hyperpnoea in the intact group was 99.1 +/- 11.8 min (P less than 0.001). The results support the idea of two central distinct areas of action of morphine in the fetal brain. The absence of hyperpnoea in the sectioned fetuses suggests that neurons inhibiting the 'respiratory neurons' are located rostrally to the mid-collicular line.

Animals↗

PubMedDate not supplied

Effects of neonatal undernutrition on the electrocortical development of the association areas in the rat.

The electrocortical effects provoked by neonatal undernutrition and the environmental sensorial stimuli were studied in the cortical association areas of developing Wistar rats. When the interaction between these two factors was interfered (Experiment 1), the average frequency of the ECoG in the early starved rats was significantly increased than controls. Moreover, if these two factors were combined (Experiment 2) not significant differences in the ECoG average frequencies were observed. The data suggest that the maturation of cells underlying the ECoG in the association areas of the rat, requires not only an adequate supply of nutrients, but also the influence of sensory cues arising from the mother, littermates and the environmental surrounding.

Animals↗

PubMed1979

Effect of arterial hypoxia on the cerebrocortical redox state, vascular volume, oxygen tension, electrical activity and potassium ion concentration.

The effect of different degrees of arterial hypoxia on cerebrocortical NAD/NADH redox state, reflectance, oxygen tension, extracellular potassium ion concentration, ECoG and arterial blood pressure was investigated in rats. The results may be summarized as follows. a) The decrease of cortical pO2 preceded the dilatation of cortical vessels by 15-20 sec but the changes in cortical extracellular potassium ion concentration, ECoG and arterial blood pressure started later than the vasodilatation. These results give further support to the regulatory role of cortical pO2 decrease in the initiation of cerebrocortical vasodilatation during arterial hypoxia. b) Since the K+ concentration of the brain cortex and the ECoG did not change in mild arterial hypoxia, the significant NAD reduction obtained in this experimental group is likely to be of cytoplasmic origin. The same conclusion applies to the initial periods of severe arterial hypoxia. On the basis of the extent of NAD reduction during various degrees of arterial hypoxia it is concluded that about 30% of the NAD reduction occurring in anoxia is of cytoplasmic origin. c) When the animals were ventilated with a gas mixture containing 4-7% oxygen, the brain cortex became nearly anoxic, partly because of the gradual decrease of arterial blood pressure. Finally, the mechanism of potassium leakage is identical under prolonged severe arterial hypoxaemia and on anoxic terminal depolarization.

Action Potentials↗

PubMed1985

[Effect of nicotine on auditory functions in the rat, studied by electrocochleography and auditory evoked potentials of the brain stem].

The rôle of nicotine (100 micrograms/kg) on brainstem auditory evoked responses (FFP) and electrocochleography (EcoG) in rats anaesthetized with pentobarbital has been studied. Each component of FFP and EcoG was analysed in terms of its latency and amplitude. Nicotine failed to produce any significant changes in the latencies of the FFP and EcoG components. Nicotine after 30 min increases significantly the amplitude I, I', II and III, of the FFP components, and decreases no significantly IV and V components. These finding suggests the presence of muscarinic and nicotinic effect of nicotine, in the mediation of the brainstem auditory pathway.

Animals↗

PubMed1989

Development of tolerance to ethanol-induced suppression of breathing movements and brain activity in the near-term fetal sheep during short-term maternal administration of ethanol.

The effect of short-term maternal ethanol administration on the ethanol-induced suppression of fetal breathing movements, electrocortical (ECoG) activity, and electroocular (EOG) activity was determined in the near-term fetal sheep. Twelve conscious instrumented pregnant ewes (between 125 and 139 days of gestation; term, 147 days) received 1-h intravenous infusion of 1 g ethanol/kg total body weight daily for six days (n = 6) or an equivalent volume of normal saline daily for six days (n = 6). On the seventh day, the ethanol- and saline-pretreated animals were administered 1 g ethanol/kg total body weight. A further six ewes received 1-h intravenous infusion of 1 g ethanol/kg total body weight (n = 3) or an equivalent volume of normal saline (n = 3) daily for thirteen days with both groups receiving 1 g ethanol/kg total body weight on day fourteen. Fetal ECoG and EOG activities, and fetal breathing movements were monitored continuously over the post- operative and experimental periods. Saline infusion had no significant effect on the parameters studied. Fetal breathing movements were suppressed for 8 h after the first ethanol dose, and were not significantly suppressed after fourteen days of once-daily, maternal ethanol administration. Low-voltage ECoG and EOG activities were suppressed for 3 h after the first ethanol dose, and were not significantly suppressed after seven days of repeated ethanol administration. Maternal and fetal blood gases and acid-base balance were not significantly affected by maternal ethanol administration. These data demonstrate that short-term maternal administration of ethanol results in the development of tolerance to ethanol in the mature fetus.

Animals↗

PubMed1988

[Quantitative characteristics of the electrocorticographic sleep stages in bottle-nosed dolphins].

Quantitative analysis of the ECoG stages in four bottle-nosed dolphins has demonstrated that unihemispheric slow-wave sleep is the dominant type of their natural sleep. All the variants of the bilateral and unilateral ECoG synchronization comprise 33.4% of the total recording time, with unilateral slow-wave sleep accounting for 28.8%. A single brain hemisphere is in a state of ECoG synchronization for 19% of the total recording time. The maximal amount of sleep is registered during a night and the second half of the day. Unihemispheric sleep episodes tend to appear alternatively in both hemispheres.

Animals↗

PubMed1987

Influence of clonazepam on electrocorticographic changes induced by metrazol in rats during ontogenesis.

The action of clonazepam (CZP) pretreatment on metrazol-induced ECoG phenomena was studied in Wistar albino rats. ECoG was recorded in acute experiments in male rats 7, 12, 18, 25 and 90 days old (N = 162). CZP (0.1 or 0.02 mg/kg) was injected i.p. 10 min prior to the start of repetitive administration of metrazol (PTZ, 20 mg/kg i.p. every 5 min). Latencies of the first signs of PTZ action, of the rhythmic metrazol activity, of the first ictal activity and of the generalized seizure were measured. CZP exhibited a dose-related effect against ECoG signs elicited by PTZ. A statistically significant increase in latencies was observed with the dose of 0.1 mg/kg in 18 day old and older animals. The 0.1 mg/kg dose of CZP also completely blocked generalized ictal activity in 7 day old rats. In adult animals, CZP pretreatment led to the appearance of partial seizures, a phenomenon never seen in controls. The development of CZP effects corresponds to the maturation of benzodiazepine binding sites.

Aging↗

PubMed1985

Effect of propranolol on brain electrical activity during hyperbaric oxygenation in the rat.

The effect of 1, 2, and 5 mg/kg propranolol on the neuroelectrophysiological manifestations of CNS oxygen toxicity was studied in conscious rats. Cortical electrodes for electrocorticographic (ECoG) recording and femoral venous cannula for i.v. infusion were implanted 7 and 3 d, respectively, before the experiment. The rats were divided into 5 groups. Groups I to III were treated with 1, 2, and 5 mg/kg propranolol, respectively, and Group IV with saline. Groups I-IV were exposed to 5 ATA O2 until the appearance of the first cortical paroxysmal electrical discharges (FED), considered to be a preconvulsive electrophysiological manifestation of CNS oxygen toxicity. Rats in Group V were exposed to 5 ATA N2-O2 normoxia and treated with 5 mg/kg propranolol. After the hyperbaric exposures and the i.v. administration of propranolol a typical ECoG pattern consisting of frequent bursts of high amplitude spindle-like waves of 6-7 c/s activity was observed. In hyperbaric oxygen-exposed rats, the paroxysmal electrical discharges were always preceded by the propranolol-induced spindle wave activity (in theta range) and oxygen-induced slow wave activity (in delta range) in ECoG. Infusion of 2 and 5 mg/kg propranolol significantly delayed the time of onset of the oxygen-induced slow wave activity and the FED. It is suggested that the protective effect of propranolol against the neurological manifestations of oxygen toxicity, may be related to its multiple effects on physiological systems rather than beta adrenergic blocking action alone.

Animals↗

PubMed1972

Orienting response hypernormality in frontal cats.

Results obtained in collaboration with B. Dreher are summarized. Ocular fixation was the indicator of the orienting response, and pupillary dilatation and ECoG arousal to olfactory stimuli were the indicators of the arousal response. To make precise recording possible, animals with pretrigeminal brain stem transection were used. After ablation of the anterior sigmoid gyrus or proreal gyrus the fixation response was enhanced and its resistance to habituation was strongly increased. On the other hand, the pupillary dilatation and ECoG arousal to olfactory stimuli and the background pupillary diameter and ECoG activity were unaffected. The hypernormality of the orienting response can be partially responsible for the disinhibition of the locomotor responses in go-no go differentiation and for the impairment of locomotor delayed responses in frontal carnivores.

Animals↗

PubMed1979

Stimulation of breathing movements in fetal sheep by inhibitors of prostaglandin synthesis.

We studied the effects of inhibitors of prostaglandin synthesis on fetal breathing movements on 17 occasions in 11 lambs (gestational age 125-141 days). We gave 12 h infusions of sodium mechlofenamate (8.6-22.2 mg.kg-1) in 13 studies and indomethacin (21.8-38.8 mg.kg-1) in four studies. Results were similar with both agents and did not correlate with drug dosage. There were no changes in fetal arterial blood pressure, pH or blood gas tensions. We assessed fetal breathing movements by measurements of tracheal pressure for a control period of 224 h prior to and 208 h during the infusion of inhibitors of prostaglandin synthesis; their administration caused a marked stimulation of fetal breathing movements judged from the following four variables: (1) incidence of fetal breathing movements increased from 38.4 to 69.2% of the time (P < 0.001); (2) average amplitude of change in tracheal pressure during fetal breathing movements increased from 4.1 to 6.0 torr (P < 0.01); (3) maximal amplitude of change in tracheal pressure during fetal breathing movements increased from 8.8 to 13.4 torr (P < 0.01); and (4) the duration of the longest continuous episode of fetal breathing movements increased from 37 to 229 min (P < 0.05). Two fetuses had electrocorticogram (ECoG) recordings. In control periods, fetal breathing movements occurred only during low voltage, high frequency ECoG activity; however, during infusions of inhibitors of prostaglandin synthesis, fetal breathing movements occurred also during high voltage, low frequency ECoG activity. We conclude that inhibitors of prostaglandin synthesis stimulate fetal breathing movement in fetal sheep. These results suggest that a component of the prostaglandin system is a factor which inhibits breathing movements during fetal life.

Animals↗

PubMed1982

Effect of prostaglandin F2 alpha and prostacyclin on asphyxic anoxia in cats.

The effects of exogenously applied prostaglandin F2 alpha (PGF2 alpha) and prostacyclin (PGI2) on asphyxic anoxia was studied in curarized and artificially ventilated cats. Anoxia was induced by stopping the ventilation and checking the changes in the EcoG. Cortical resistance (CRs) was evaluated as time between stopping the ventilation and the extinction of ECoG. Cortical recovery (CRc) was expressed as time between restitution of ventilation and reappearance of brain activity. Anoxia resistance index (ARI) was defined as the ratio between these two parameters (CRs/CRc). PGF2 alpha was applied by 5 minute i.v. and intracarotid (i.c.) infusion in a dose of 10 micrograms/kg/min, and PGI2 in a dose of 250 ng/kg/min for 15 minutes intracarotidly. The results show that both the i.c. and i.v. infusion with PGF2 alpha led to a significant decrease of CRs and prolongation of CRc resulting in decrease of ARI. The changes are more expressed at i.v. infusion, PGI2 does not improve the ECoG changes evoked by hypoxia. Suggestions for the possible mechanism of PGF2 alpha action and for the failure of PGI2 to protect the brain are made.

Animals↗

PubMed1981

The effect of brief episodes of diminished uterine blood flow on breathing movements, sleep states and heart rate in fetal sheep.

Responses to brief episodes of occlusion of the middle uterine artery were examined in six fetal sheep in utero between 122 and 140 days of gestation. Continuous recordings were made of fetal breathing movements, electro-cortical (ECoG) and electro-ocular (EOG) activity, arterial pressure and heart rate. Five minutes of unilateral or bilateral arterial occlusion caused fetal hypoxaemia while changes in mean arterial PCO2 and pH were not statistically significant. Occlusions usually led to a cessation of rapid eye movements (REM) and respiratory activity (86% of trials), to the appearance of high-voltage slow waves in the ECoG (84% of trials) and to a fall in heat rate of more than 10% (81% of trials). With the exception of the changes in heart rate, these responses resemble those which frequently occur during non-labour contractions of the uterus. We conclude that the cessation of fetal breathing movements and rapid eye movements and the onset of slow waves in the ECoG seen in association with uterine contractions may be due to the mild hypoxaemia which accompanies them.

Animals↗

PubMed1995

Results of cortical resection for intractable epilepsy using intra-operative corticography without chronic intracranial recording.

Twenty-four patients with intractable partial epilepsy underwent surgery between 1969 and 1988. Localization was by non-invasive means using scalp EEG and CT. In 12 cases the focus was temporal and in eight frontal. Craniotomy was undertaken with intraoperative electrocorticography (ECoG). Ten cases had a standard temporal lobectomy, seven a topectomy, four topectomy with tumour excision and one tumour excision alone. Two cases did not have a resection. Pathology revealed a mass lesion in 12 cases, hippocampal sclerosis in two and gliosis in six. Mean length of follow-up was 7.4 was. Fourteen patients (64%) were seizure free, two (9%) almost seizure free, four (18%) had worthwhile improvement and two (9%) no improvement. Of the temporal resections, 9 out of 12 (75%) were seizure free and of the extratemporal resections 5 out of 10 (50%) were seizure free. Removal of a mass lesion carried the most favourable prognosis for seizure outcome: 10 our of 12 (83%) of the cases with mass lesions, but 3 out of 6 (50%) of the cases with gliosis were seizure free. In two of the frontal resections removal of tumour resulted in disappearance of contralateral frontal independent spikes. It is concluded that where sufficient information exists to localize seizure activity by non-invasive means, invasive recording is unnecessary. The utility of intraoperative ECoG is discussed. It may be of limited use in cases of standard resection of when a mass lesion is present, but ECoG can prove useful to delineate the epileptogenic area in cases where there is o mass lesion and the results can still be rewarding.

Adolescent↗