Sleep and epilepsy: A key role for nitric oxide?

PURPOSE: It has been suggested that nitric oxide (NO) is involved in sleep mechanisms and in the pathophysiology of epilepsy. Data are, however, controversial because it is not clear whether NO facilitates sleep or waking, or whether it exerts pro-or antiepileptic influences. METHODS: The question was considered through NO voltammetric measurements and electroencephalographic recordings performed in GAERS rats (Genetic Absence Epilepsy Rat from Strasbourg): an experimental model of "petit-mal" human disease. Regulatory processes of sleep and epilepsy were studied after administration of a NO synthase inhibitor [l-arginine-p-nitroanilide (l-ANA) 100 mg/kg i.p.], a NO donor (SIN-1 100 ng/2 microl i.c.v.), and the antiepileptic drugs used in clinic [valproate (VPA 200 mg/kg i.p.) and ethosuximide (ESM 100 mg/kg i.p.)]. RESULTS: In GAERS rats, spontaneous circadian organizations of spike-wave discharges and paradoxical sleep (PS) occur in an opposite way; spontaneous NO concentrations are higher during seizures than during wakefulness, slow-wave sleep, and PS, respectively. l-ANA induces a disappearance of NO peak, an epileptic induction, and a loss of PS while SIN-1 induces opposite effects. Antiepileptic effects of VPA and ESM are associated with a PS increase and a significant release of NO. CONCLUSIONS: These results indicate that NO could be, in GAERS rats, a central piece in the reciprocal inhibitory mechanisms regulating the induction of PS and spike-wave discharges. NO could prevent absence epilepsy and act as an antiepileptic substance in facilitating PS. Antiepileptic efficiency of VPA and ESM may work through their ability to release NO. A track for a new treatment of petit-mal disease in children can be envisioned.

Differential pulse voltammetry in vivo with working carbon fiber electrodes: 5-hydroxyindole compounds or uric acid detection?

Differential pulse voltammetry was performed in rats chronically implanted with carbon fiber electrodes in the caudate (n.Cd) and raphe dorsalis (n.RD) nuclei. The electrochemical signal obtained at the +300 mV potential (peak 3) in animals implanted for more than one week (long term chronic conditions, greater than 7 days) could be dependent upon the extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in n.Cd and n.RD. This result was obtained despite the tendency of Pargyline to increase n.Cd and n.RD endogenous concentrations of Uric Acid (UA) measured by High Performance Liquid Chromatography (HPLC). In contrast, in animals implanted for less than one week (short term chronic conditions, less than 7 days) peak 3 recorded in the same structure could be dependent upon extracellular fractions of 5-HIAA and UA since consecutive injections of Pargyline and Allopurinol are necessary to suppress this signal. The source of extracellular UA measured in brain by voltammetry, in such short term chronic conditions, might result from surgical trauma.

Factors influencing the properties of voltammetric carbon fibre electrodes: the importance of the pH of the medium used for the electrical treatment and of the resin coating of the fibres.

Electrical treatment of resin-coated voltammetric carbon fibre electrodes with triangular voltage at low (1.1) pH resulted in electrodes almost insensitive to ascorbic acid (AA) and dihydroxyphenylacetic acid (DOPAC) while their response to 5-hydroxyindoleacetic acid (5-HIAA) was practically the same as after treatment in the usually employed pH 7.4 medium. Electrodes treated at high pH (12.0), on the other hand, were more sensitive to AA and DOPAC than those treated at pH 7.4 and less sensitive to 5-HIAA. Exposing resin-coated electrodes to the treatment media without electrical treatment was not sufficient to obtain the same results as with the application of the current. Electrodes without resin coating were sensitive to AA without electrical treatment while coated electrodes were not. Electrical treatment increased the sensitivity of non-coated electrodes and rendered coated electrodes even more sensitive than non-coated ones. Treatment of coated electrodes for a maximum sensitivity to 5-HIAA was found to require less time than to obtain maximum sensitivity to the other compounds. Present results suggest that it is possible to prepare selective voltammetric electrodes by choosing the right parameters for their electrical pretreatment.

[Differential pulse voltammetry: focus on the measurement of 5-hydroxyindole compounds and uric acid in the brain]. / Voltamétrie impulsionnelle différentielle: mise au point concernant la mesure des composés 5-hydroxyindols et de l'acide urique au niveau du cerveau.

The electrochemical signal obtained at the +300 mV potential (peak 3) in rats implanted for more than one week could be dependent upon extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in caudate and raphe dorsalis nuclei. In contrast, in rats implanted for less than one week, this signal could be dependent upon extracellular fractions of 5-HIAA and uric acid since consecutive injections of Pargyline and Allopurinol are necessary to suppress it.

Temperature-dependent variations of 5-hydroxyindoles in ventricular cerebrospinal fluid--an in vivo voltammetric study.

The in vivo voltammetric signal of 5-OH-indoles increased or decreased in the ventricular cerebrospinal fluid when body temperature was artificially increased or decreased in rats in acute experiments. The increase of the signal occurring after raising the body temperature was facilitated by premedication with the monoamine oxidase inhibitor pargyline. It was not abolished by pretreatment with the serotonin synthesis inhibitor para-chlorophenylalanine, although the latter caused an 85% decrease of ventricular 5-OH-indole level. No similar effects were demonstrable in the 5-OH-indole signal of the caudate nucleus recorded simultaneously. An increase of the 5-OH-indole peak was found also in animals chronically implanted with voltammetric electrodes when the ambient temperature was increased in their cages. According to the results of in vitro experiments, a direct physical effect of changes in brain temperature on the sensitivity of the voltammetric electrodes cannot account for changes found in the cerebrospinal fluid. These data, therefore, demonstrate that the increase of body temperature is followed by an increase of 5-OH-indole concentration in the ventricular cerebrospinal fluid. The in vivo voltammetric technique appears to be a suitable method for studying the serotonergic mechanisms involved in thermoregulatory processes.

Voltammetric measurements of 5-hydroxyindole compounds in the suprachiasmatic nuclei: circadian fluctuations.

This study concerns the voltammetric signal appearing at a +300 mV potential (peak 3) recorded from the suprachiasmatic nuclei (SCN) of rats under acute and chronic conditions. In acute conditions, and in order to accurately localize the working electrode, a topographical study of the peak 3 height was first realized in the frontal plane containing the SCN by use of differential pulse voltammetry and monocarbon fiber electrodes. In the same conditions, the effects of clorgyline and reserpine were studied. Clorgyline decreased peak 3 while reserpine increased it. Contrary to 5-HT, 5-HIAA contents of the SCN, measured with high performance liquid chromatography, demonstrate analogous variations. All these data suggest that it is essentially 5-HIAA which is responsible for peak 3 from the SCN. In unanesthetized, freely moving rats, under a 12/12 h light-dark cycle, spontaneous and circadian variations of the SCN's peak 3 were studied, during the rest-activity cycle. Multifiber working electrodes were used for this purpose. During spontaneous and successive periods of rest and activity peak 3 height was always found to be higher during activity. Further, these spontaneous variations were superimposed with a circadian variation exhibiting its acrophasis during the dark period. Our data suggest that the release and catabolism of serotonin is greater in waking than in sleeping animals. They also suggest, that the rostral raphe system, phase locked with the SCN, plays an important role in the circadian variations measured.

[Voltammetric detection of extracellular 5-hydroxyindole compounds at the level of cell bodies and the terminals of the raphe system: variations during the wake-sleep cycle in the rat in chronic experiments]. / Détection voltamétrique des composés 5-hydroxyindols extracellulaires au niveau des corps cellulaires et des terminaisons du système du raphé: variations pendant le cycle veille-sommeil chez le Rat en expérimentation chronique.

In rats, chronically implanted for measurements of both voltammetric and polygraphic parameters, variations of the electrochemical signal corresponding to extracellular 5-hydroxyindole compounds (peak 3) were measured during the sleep-waking cycle. The higher amplitude of this signal is always measured during waking. It decreases during slow-wave sleep (20 to 30%) and reaches its lower value during paradoxical sleep (30 to 40%). This phenomenon has been found in all structures investigated, cerebral cortex, caudate nuclei, dorsal hippocampus, suprachiasmatic nuclei, cerebellum, nuclei raphe dorsalis, centralis, pontis and magnus.

Alterations in the sleep-waking cycle induced by cooling of the locus coeruleus area.

Bilateral or unilateral, localized and reversible cooling (+10 degrees C) of the anterior part of the locus coeruleus area (LCp) in the cat induced, in rapid succession, slow wave sleep (SWS) and a transitory phase of SWS + PGO. These states of sleep were followed in 40-50% of the animals by paradoxical sleep (PS). These effects (on SWS, SWS + PGO and PS) occurred following repetitive periods of short duration cooling and were maintained during long duration cooling (70 min). Unilateral cooling of the ventral part of the locus coeruleus area (LC alpha) and peri-LC alpha induced wakefulness, regardless of the states of sleep in which the cooling was performed. After a cryolesion (-24 degrees C) of the nucleus raphe dorsalis, cooling of the LCp did not induce a hypnogenic effect. Electrical stimulation of the locus coeruleus area, however, always induced wakefulness.

Differential pulse voltammetry in brain tissue. II. Detection of 5-hydroxyindoleacetic acid in the rat striatum.

Differential pulse voltammetry with electrochemically treated carbon fiber electrodes was used to study, in anesthetized rats, the alterations of the striatal electrochemical signal appearing at +300 mV (peak 3), following pharmacological manipulation of the animals. Decreases in peak 3 were obtained after injections of NSD 1015, Ro 4-4602 and Clorgyline. This, in conjunction with biochemical measurements, suggested that 5-hydroxyindoleacetic acid (5-HIAA) is, to a considerable extent, responsible for this electrochemical signal. Increases in peak 3 obtained after reserpine, L-tryptophan and D,L-5-HTP, as well as biochemical data reinforced this hypothesis, as did the detection of peak 3 in cerebrospinal fluid and its increase after probenecid injection. The occurrence of a feed-back mechanism is discussed following injection of D,L-5-HTP.

Differential pulse voltammetry in brain tissue. I. Detection of 5-hydroxyindoles in the rat striatum.

In vitro, differential pulse voltammetry combined with electrochemically treated carbon fiber electrodes enabled detection, in different solution of 5-hydroxyindole compounds, of an oxidation peak 3 at +300 mV. In vivo, a striatal peak 3 was also recorded at this potential. Electrolytic or 5,7-dihydroxytryptamine lesions interrupting the medial forebrain bundle (MFB) were followed by a decrease of 65% and 64% in peak height, but not elimination of the peak. Biochemical determinations were significantly correlated to the peak 3 measurements. The existence of peak 3 as well as hydroxyindole compounds in blood suggested a blood contamination under the experimental conditions employed. This possibility is confirmed both by the complete disappearance of striatal peak 3 in animals with the MFB lesioned and surgically prepared a week before recordings, and by biochemical measurements in parachlorophenylalanine-treated or perfused (phosphate-buffered saline solution) animals.

Single unit recordings in the nuclei raphe dorsalis and magnus during the sleep-waking cycle of semi-chronic prepared cats.

Single unit recordings were performed in the nuclei raphe dorsalis (RD) and raphe magnus (RM) of semi-chronic prepared cats during spontaneous or cryogenically induced sleep. Of the RD neurons 75% showed a discharge pattern which decreased during slow wave sleep and paradoxical sleep (PS); such a decrease in spiking was related to the occurrence of ponto-geniculo-occipital (PGO) waves. to the contrary, 78% of the RM neurons demonstrated a discharge pattern which significantly increased during PS, and especially when PGO waves were present.

In vivo measurements by differential pulse voltammetry of extra-cellular 5-hydroxyindoleacetic acid in the rat brain.

The use of differential pulse voltammetry, performed with electrochemically treated carbon fiber electrodes, enables us to detect in vitro or in vivo, in the striatum of anaesthetized rats, an oxidation peak (3) at a potential of + 300 mV. Electrolytic or 5-7-dihydroxytryptamine lesions of the medial forebrain bundle are followed by a decrease of 59 and 62% respectively of this peak. Biochemical measurements are significantly correlated with the measured peak (3) and decreases. Thus, peak (3) increases obtained after injection of L-tryptophan and/or Reserpine, as well as the decreases observed after injection of Clorgyline or 3-hydroxybenzylhydrazine, confirm that peak (3) is dependent upon 5-hydroxyindoleacetic acid concentration. The detection of a peak (3) in the cerebrospinal fluid and its increase after injection of Probenecid reinforce this conclusion.

Absence of light-dark entrainment on the sleep-waking cycle in mice with intact visual perception.

The influence of the light-dark schedule (12 h-12 h) on the sleep-waking cycle has been studied in anophthalmic mice: the 'eyeless' ZRDCT/An strain. The complete anophthalmic mice or the heterozygotous mice of the same strain with unilateral or bilateral eyeballs present a circadian organization of the sleep-waking cycle which is not dependent on the light-dark cycle. These results are different from sleep rhythms of C57Br mice recorded under the same experimental conditions. They indicate that the structures responsible for the circadian rhythmicity of sleep exist in all the 'eyeless' ZRDCT/An mice, but are not functionally linked with the visual system even in the mice with unilateral and bilateral eyeballs.

An analysis of the carbachol-induced emotional-defensive response in cats: dependence of the response on different solvents of carbachol.

The effect of intrahypothalamic injections of carbachol (25.1 nmole into each hemisphere) dissolved in three different solvents (artificial cerebrospinal fluid, physiological saline and bidistilled water) was investigated. The purpose of this study was to find out whether the qualitative and/or quantitative character of the carbachol-induced emotional-defensive behavior depended on the sort of the solvent used. The analysis was performed on the basis of behavioral and electroencephalographic changes. Apart from routine EEG recordings, integrated measurements of the amplitude of alpha, beta, delta, and theta waves recorded rom the posterior hypothalamus, the midbrain central gray matter and from the dorsal hippocampus were performed as well as quantitative measurements of the characteristic growling. Intrahypothalamic injections of carbachol, independently of the solvent used, evoked similar vegetative, behavioral and electroencephalographic changes (in the routine recordings). The number of growls and the total duration of growling did not differ significantly either. Some statistically significant changes were found in the integrated amplitudes of EEG waves. They concerned, however, only alpha and theta rhythms and appeared in the midbrain central gray matter. Moreover, they did not affect the time course and the quantitative and qualitative features of the evoked emotional-defensive response. All used solvents are equivalent and may be applied interchangeably in experiments of this type.

[In vivo measurement, by differential pulse voltammetry, of 5-HIAA in the striatum of the rat]. / Mesure in vivo, par voltamétrie impulsionnele différentielle du 5-HIAA dans le striatum du rat.

Differential pulse voltammetry, performed with electrically treated carbon fiber electrodes, enables us to detect in vitro or in vivo in the striatum of anesthetized Rats, an oxidation peak 3 at a potential of +300 mV. Electrolytic, or 5,7-dihydroxytryptamine lesions of the medial forebrain bundle are followed by a decrease of respectively 59 and 62% of this peak. Biochemical measurements are significantly correlated to the measured peaks 3 and troughs. Thus, peak 3 increases obtained after injection of L-tryptophane and/or reserpine, as well as the troughs observed after injection of clorgyline and/or NSD 1015 confirm that the peak 3 is dependent upon 5-hydroxyindolacetic acid (5-HIAA) concentration.