Anticonvulsant and antilethal effects of the phencyclidine derivative TCP in soman poisoning.

The protection afforded by TCP (thienylcylohexylpiperidine), a non-competitive blocker of N-methyl-D-aspartate (NMDA) receptors, against the seizures and lethality produced by 2 x LD50 of soman (62 micrograms/kg, sc), an irreversible inhibitor of cholinesterase, was studied in guinea-pigs. In the presence of additional anticholinergic medication (pyridostigmine: 0.2 mg/kg, sc, 30min prior to soman; atropine sulphate: 5mg/kg, im, 1 min post-soman), TCP pretreatment (2.5mg/kg, im, 30 or 15 min prior to soman) did not generally prevent the appearance of soman-induced status epilepticus but did arrest it after 30-40 min in 80% (TCP-30min) or 100% (TCP-15min) of the convulsing subjects. Moreover, in all subjects treated curatively, TCP was able to interrupt ongoing status epilepticus in approximately 20, 10 or 8 min when it was administered 5, 30 or 60min respectively after the onset of epileptiform tracings on EEG. All of these curatively administered animals survived and recovered remarkably well. On every criteria examined (latency-to-seizure arrest, 24hr-survival rate, clinical recovery), injection of 2.5mg/kg TCP after 90min of seizures appeared slightly less efficient compared to earlier curative administration. Therefore, our study (a) establishes that the previously reported capacity of MK-801 (dibenzocyclohepneimine) to counteract soman toxicity is not unique and could be extended to other non-competitive inhibitors of NMDA receptors; (b) shows that TCP could easily prevent and, above all, interrupt soman-induced seizures; furthermore, TCP appears the first compound ever tested on soman poisoning that still displays satisfactory anticonvulsant activity after such a long duration of initial status epilepticus (90min); therefore, TCP might be of special value for the delayed therapy for soman poisoning; (c) confirms that NMDA receptors are involved in the maintenance of seizures and play an important role in other processes implicated in the overall toxicity (including the lethal respiratory effects) of soman poisoning.

Neuroprotective activity of glutamate receptor antagonists against soman-induced hippocampal damage: quantification with an omega 3 site ligand.

Previous investigations have indicated that the measurement of omega 3 (peripheral-type benzodiazepine) binding site densities could be of widespread applicability in the localization and quantification of neural tissue damage in the central nervous system. In the first step of the present study, the suitability of this approach for the assessment of soman-induced brain damage was validated. Autoradiographic study revealed marked increases of omega 3 site densities in several brain areas of convulsing rats 2 days after soman challenge. These increases were well-correlated with the pattern and the amplitude of neuropathological alterations due to soman and closely related to both glial reaction and macrophage invasion of the lesioned tissues. We then used this marker to assess, in mouse hippocampus, the neuroprotective activity against soman-induced brain damage of NBQX and TCP which are respective antagonists of non-NMDA and NMDA glutamatergic receptors. Injection of NBQX at 20 or 40 mg/kg 5 min prior to soman totally prevented the neuronal damage. Comparatively, TCP had neuroprotective efficacy when administered at 1 mg/kg 5 min prior to soman followed by a reinjection 1 h after. These results demonstrate that both NBQX and TCP afford a satisfactory neuroprotection against soman-induced brain damage. Since it is known that the neuropathology due to soman is closely seizure-related, the neuroprotective activities of NBQX and TCP are discussed in relation with the respective roles of non-NMDA and NMDA receptors in the onset and maintenance of soman-induced seizures.

Influence of medial septal cholinoceptive cells on c-Fos-like proteins induced by soman.

The effects of intraseptal application of atropine on c-fos proto-oncogene expression related to soman treatment were studied by immunohistochemistry for c-Fos-like proteins. In control rats, 2 h after the onset of convulsion, c-Fos-like immunoreactivity was intense in the piriform and entorhinal cortices, but also in the cingulate, frontoparietal and retrosplenial cortices. In addition, the staining was moderate in the hypothalamus, amygdala and fascia dentata. The intraseptal application of atropine, which prevented soman-induced convulsions, reduced or even blocked c-Fos-like protein production related to soman treatment. This inhibition of Fos induction was significant in most of the limbic structures but also in non-limbic areas. The data in this study strongly suggest that the cholinergic cells of the medial septal area play a key role in soman-induced seizures, and confirm that c-Fos-like protein induction is closely related to neuronal hyperactivity.

Changes in hippocampal acetylcholine and glutamate extracellular levels during soman-induced seizures: influence of septal cholinoceptive cells.

The changes in extracellular acetylcholine and glutamate levels were determined, during the course of seizures induced by soman, an irreversible inhibitor of acetylcholinesterase, in the CA1 hippocampal area of rats previously injected with atropine or normal saline into septum. The marked increases observed in soman-treated animals were abolished in rats receiving atropine. These data strongly suggest that, during soman intoxication, septal cholinoceptive cells play a key role in controlling the release of acetylcholine and glutamate in hippocampus. The mechanisms underlying this phenomenon are discussed.

The posterior hypothalamus is responsible for the increase of brain temperature during paradoxical sleep.

Electroencephalogram, caudate nucleus temperature (Tc), ear skin temperature (Te) as well as cerebral blood flow (CBF) measured by a thermal clearance method, were recorded simultaneously and continuously in cats. After baseline recording in which we confirmed the increase of Tc during paradoxical sleep (PS), neuronal cell bodies of the mesencephalic reticular formation and/or the posterior hypothalamus (PH) were destroyed with ibotenic acid. Only PH lesions were followed by either a suppression of the increase or even a decrease of Tc during PS while Te variations were not modified. The decrease in CBF, which was always associated with Tc increase, was suppressed after the PH lesion. These results led us to the conclusion that the increase of Tc at the onset of PS is due to a decrease in CBF. Furthermore, it may be hypothesized that the decrease in CBF depend upon an active vasoconstriction process originating in the PH.

Neurotoxic lesion of the mesencephalic reticular formation and/or the posterior hypothalamus does not alter waking in the cat.

In order to re-evaluate the role of two putative waking systems, we injected a neural cell body toxin, ibotenic acid (IA) (45 micrograms/microliters), into the mesencephalic reticular formation (MRF) and/or the posterior hypothalamus (PH). On the one hand, when the cell body destruction was only restricted to the MRF, the IA microinjection was followed by a temporary high voltage and slow neocortical electroencephalogram (EEG) during the first 24 postoperative hours and by a subsequent long term increase in waking which lasted 8-12 h. After the first postoperative day, there were no motor disturbances, no aphagia nor adypsia, no alteration of cortical activation and no modification of thermoregulation or of the sleep-waking cycle. On the other hand, the IA microinjection into the PH induced a hypothermia during the first postoperative night and a dramatic transient hypersomnia immediately after the disappearance of the anesthesia (14-24 h after the IA injection). On the third day, all cats recovered control level of paradoxical sleep (PS), slow wave sleep (SWS) and cerebral temperature. They presented normal motor behavior but they were not able to eat by themselves during the first postoperative week. Finally, when the lesions of the MRF and the PH were realized in one single operation, the cats were first motionless in a comatose state for 2-3 days. This state was accompanied by a transitory hypothermia and the suppression of a spontaneous or evoked cortical low voltage fast activity. However, from the 2nd postoperative week, both behavioral and EEG waking re-occurred. By contrast, the two successive operations (MRF followed by PH) did not induce a comatose state. We did not observe any deficit in motor behavior, and the sleep-waking cycle was quite normal as from the second postlesion day. In the MRF-PH-lesioned cats, the injection of alpha-methyl-p-tyrosine (150 mg/kg) induced a large decrease in waking and a moderate increase in PS. In the MRF-lesioned cats, IA produced a large area of cell body loss, centered in the MRF, that extended from levels A2 to A6 of stereotaxic planes and sometimes encroached upon the red nucleus and the substantia nigra. In the PH-lesioned cats, the histological analysis revealed a great loss of cell bodies in the PH extended from levels A8 to A12.5. The damage included the lateral and posterior hypothalamic areas and sometimes the tuberomamillary nucleus. In MRF- and PH-lesioned cats, the cell body loss extended from levels A2 to A12.5.(ABSTRACT TRUNCATED AT 400 WORDS)

Aromatic L-amino acid decarboxylase-immunohistochemistry in the cat lower brainstem and midbrain.

By indirect immunohistochemistry, the present study examined the distribution of neuronal structures in the cat medulla oblongata, pons, and midbrain, showing immunoreactivity to aromatic L-amino acid decarboxylase (AADC), which catalyzes the conversion of L-3, 4-dihydroxyphenylalanine (L-DOPA) to dopamine, and 5-hydroxytryptophan to serotonin (5HT). With simultaneous and serial double immunostaining techniques, immunoreactivity to this enzyme was demonstrated in most of the catecholaminergic and serotonergic neurons. We could also demonstrate AADC-IR cell bodies that do not contain tyrosine hydroxylase (TH-) or 5HT-immunoreactivity (called "D-type cells") outside such monoaminergic cell systems. At the medullo-spinal junction, very small D-type cells were found within and beneath the ependymal layer of the 10th area of Rexed surrounding the central canal. D-type cells were localized in the caudal reticular formation, nucleus of the solitary tract, a dorsal aspect of the lateral parabrachial nucleus, and pretectal areas as have been reported in the rat. Furthermore, the present study describes, in the cat brainstem, new additional D-type cell groups that have not been reported in the rat. Dense or loose clusters of D-type cells were localized in the external edge of the laminar trigeminal nucleus, dorsal motor nucleus of the vagus, external cuneate nucleus, nucleus praepositus hypoglossi, central, pontine, and periaqueductal gray, superficial layer of the superior colliculus, and area medial to the retroflexus. D-type cells were loosely clustered in the lateral part of the central tegmental field dorsal to the substantia nigra, extending dorsally in the medial division of the posterior complex of the thalamus and medial side of the brachium of the inferior colliculus. They extended farther rostrodorsally along the medial side of the nucleus limitans and joined with the pretectal cell group. Almost all these cells were very small and ovoid to round with 1-2 short processes with the exception of dorsal motor vagal cells. AADC-IR axons were clearly identified in the vagal efferent nerves, longitudinal medullary pathway, dorsal tegmental bundle rostral to the locus coeruleus. Serotonergic axons were identified not only in the central tegmentum field and lateral side of the central superior nucleus, but also in the ventral surface of the medulla oblongata. We describe principal densely stained fiber plexuses in the cat brainstem. The findings of the present study provide a morphological basis for neurons that decarboxylate endogenous and exogenous L-DOPA, 5HTP, and other aromatic L-amino acids.

Reversibility of para-chlorophenylalanine-induced insomnia by intrahypothalamic microinjection of L-5-hydroxytryptophan.

Para-chlorophenylalanine, a blocker of serotonin biosynthesis by inhibiting tryptophan hydroxylase, induced total insomnia which was accompanied in cat by a permanent discharge of ponto-geniculo-occipital activity. L-5-Hydroxytryptophan microinjection (1-4 micrograms/0.5 microliters) in the anterior hypothalamus 72 h after para-chlorophenylalanine administration, restored both slow wave sleep and paradoxical sleep with variable latencies for each state of sleep. On the contrary, ponto-geniculo-occipital activity was never suppressed. The hypnogenic effects of L-5-hydroxytryptophan were always followed by a return of the para-chlorophenylalanine-induced insomnia. On the other hand, the temperature recording did not show any alteration of the cerebral temperature after para-chlorophenylalanine treatment but the subsequent L-5-hydroxytryptophan microinjection was followed by hyperthermia. Using immunohistochemistry for serotonin after intrahypothalamic L-5-hydroxytryptophan microinjection in parachlorophenylalanine-pretreated cat, we defined a restricted region of the anterior hypothalamus possibly responsible for the hypnogenic effect. This region included the lateral hypothalamus and the anterior hypothalamic area. It is suggested that the reversible hypersomnia after L-5-hydroxytryptophan microinjection in the anterior hypothalamus in para-chlorophenylalanine-pretreated cat is due to a neurohormonal action of serotonin: serotonin could act upon the anterior hypothalamus which secondarily inhibits a waking system located in the ventrolateral hypothalamus leading to the appearance of paradoxical sleep.

[The destruction of perikaryas of the mesencephalic reticular formation and the posterior hypothalamus does not cause major disorders of awakening in the cat]. / La destruction des périkaryas de la formation réticulée mésencéphalique et de l'hypothalamus postérieur n'entraîne pas de troubles majeurs de l'éveil chez le chat.

Ibotenic acid microinjections have been realized at the level of the mesencephalic reticular formation and the posterior hypothalamus in 7 cats. This technique has led to a quasi-total destruction of cell bodies in the two areas (including the histaminergic neurons). 2 to 3 days after such lesions, there were no major effects on behavioral waking. These results do not favor the hypothesis of the existence of a waking system at the level of the mesencephalic reticular formation and/or posterior hypothalamus.

Long-lasting insomnia induced by preoptic neuron lesions and its transient reversal by muscimol injection into the posterior hypothalamus in the cat.

In order to analyse the role of the anterior hypothalamus in the regulation of the sleep-waking cycle we made bilateral neuronal lesions at different levels of the anterior hypothalamus in cats, by means of microinjections of a cell-specific neurotoxin:ibotenic acid. These lesions resulted in severe insomnia in eight cats. This insomnia was characterized by a large decrease or even disappearance of paradoxical sleep and deep slow wave sleep and, to a lesser extent, by a decrease of light slow wave sleep, for 2-3 weeks. In the other five animals, we observed a large reduction of deep slow wave sleep (0-40% of control level), but a less intensive decrease of time spent in paradoxical sleep (50-75% of control level) and no marked effect on light slow wave sleep. During the first 3-6 postoperative days we also noticed hyperthermia in all cats; thereafter, the animals presented only a slight increase in brain temperature which did not appear to trigger the sleep impairment. Histological analysis of the different lesions revealed that the insomnia could be attributed to neuronal cell body destruction in the mediobasal part of the anterior hypothalamus covering; the medial preoptic area and a narrow portion of the lateral preoptic area as well as a restricted part of the anterior hypothalamic nucleus. In order to investigate the putative role of the posterior hypothalamic structures in the mechanism of insomnia after lesion of the mediobasal preoptic area neurons we injected an agonist of GABA into the ventrolateral part of the posterior hypothalamus to locally depress the neuronal activity. The bilateral intracerebral microinjection of muscimol (0.5-5 micrograms) induced a transient intensive hypersomnia (slow wave sleep and paradoxical sleep). These findings indicate that neuronal cell loss in the mediobasal preoptic area induced a long lasting insomnia. Thus, it may be hypothesized that the integrity of this structure is necessary for sleep appearance. Finally, our data are in keeping with an intrahypothalamic regulation of the sleep-waking cycle.

5-Hydroxytryptophan uptake and decarboxylating neurons in the cat hypothalamus.

Parachlorophenylalanine, an inhibitor of tryptophan hydroxylase, induced a virtually total disappearance of serotonin-immunoreactivity in the hypothalamus of the cat. After intrahypothalamic injection of 5-hydroxytryptophan, an immediate precursor of serotonin in cats pretreated with parachlorophenylalanine, serotonin-immunoreactivity was detected in many fibers surrounding the injection site. Furthermore, when 5-hydroxytryptophan was injected with inhibitor of monoamine oxidase, a large number of small neurons immunoreactive to serotonin was identified in many discrete regions: the anterior and lateral hypothalamic areas, preoptic area, suprachiasmatic nucleus, dorsal hypothalamic area, dorsomedial nucleus, posterior hypothalamic area and nucleus of the fields of Forel. Serotonin-immunoreactivity was also evident in the thick axon bundles in the lateral hypothalamus. The distribution pattern of these cells was quite similar to that of aromatic L-amino acid decarboxylase, which catalyses the conversion of 5-hydroxytryptophan to serotonin and that of L-3,4-dihydroxyphenylalanine to dopamine. However, we failed to demonstrate serotonin-immunoreactivity in these parvocellular neurons without monoamine oxidase inhibitor. It is possible that 5-hydroxytryptophan is decarboxylated to serotonin by aromatic L-amino acid decarboxylase but rapidly degraded by monoamine oxidase-A, the enzyme which preferentially deaminates serotonin. In contrast, serotonin-immunostaining was always demonstrable after intrahypothalamic injection of 5-hydroxytryptophan without monoamine oxidase inhibitor in magnocellular neurons located in the ventrolateral posterior hypothalamus and which contain exclusively monoamine oxidase-B and histidine decarboxylase. It appears that in these cells and axons, serotonin, possibly formed by histidine decarboxylase, is not rapidly oxidized by monoamine oxidase-B. Possible roles of serotonin as a neurohormone in sleep-waking regulation and of trace amines in the brain are discussed.

Hypophysectomy does not disturb the sleep-waking cycle in the cat.

The ablation of the hypophysis does not disturb the basic waking-sleep cycle. Further, this intervention fails to modify the recovery of sleep after instrumental paradoxical sleep deprivation as well as after injection of 5-hydroxytryptophan in parachlorophenylalanine-pretreated insomniac cats. These results demonstrate that the hypophysis does not play a significant role in sleep mechanisms. We discuss these data in view of a possible regulation of the sleep-waking cycle by hypothalamo-hypophyseal hormones.

Immunohistochemistry of aromatic L-amino acid decarboxylase in the cat forebrain.

The topographic distribution of aromatic L-amino acid decarboxylase (AADC)-immunoreactive (IR) neurons was investigated in the cat hypothalamus, limbic areas, and thalamus by using specific antiserum raised against porcine kidney AADC. The perikarya and main axons were mapped on an atlas in ten cross-sectional drawings from A8 to A16 of the Horsley Clarke stereotaxic plane. AADC-IR neurons were widely distributed in the anterior brain. They were identified in the posterior hypothalamic area, rostral arcuate nucleus of the hypothalamus, dorsal hypothalamic area, and periventricular complex of the hypothalamus, which contain tyrosine hydroxylase (TH)-IR cells and are known as A11 to A14 dopaminergic cell groups. AADC-IR perikarya were also found in the other hypothalamic areas where few or no TH-IR cells have been reported: the supramamillary nucleus, tuberomamillary nucleus, pre- and anterior mamillary nuclei, caudal arcuate nucleus, dorsal hypothalamic area immediately ventral to the mamillothalamic tract, anterior hypothalamic area, area of the tuber cinereum, retrochiasmatic area, preoptic area, suprachiasmatic and dorsal chiasmatic nuclei. We also identified them in the anterior commissure nucleus, bed nucleus of the stria terminalis, stria terminalis, medial and central amygdaloid nuclei, lateral septal nucleus, and nucleus of the diagonal band of Broca. AADC-IR neurons were localized in the ventromedial part of the thalamus, lateral posterior complex, paracentral nucleus and lateral dorsal nucleus of the thalamus, medial habenula, parafascicular nucleus, subparafascicular nucleus, and periaqueductal gray. Conversely, we detected only a few AADC-IR cells in the supraoptic nucleus whose rostral portion contains TH-IR perikarya. Comments are made on the relative localizations of the AADC-IR and TH-IR neurons, on species differences between the cat and rat, as well as on the possible physiological functions of the enzyme AADC.

Visualization of tyrosine hydroxylase-immunoreactive neurons in the cat dorsal motor vagal cells after treatment with parachlorophenylalanine.

We examined tyrosine hydroxylase-immunoreactive (TH-IR) neuronal structures in the cat dorsal motor nucleus of the vagus (DMV) and its adjacent regions. We identified only a few in the caudal part of the DMV and no TH-IR cells at all in its rostral portion. However, after treatment with parachlorophenylalanine (PCPA), numerous TH-IR perikarya were visualized in the DMV. Comments are made on the central catecholamine regulation and the possible influence of serotonin afferents on this nucleus.

[The value of respiratory function tests in the surveillance of asthmatic children]. / Intérêt de l'exploration fonctionnelle respiratoire dans la surveillance des enfants asthmatiques.

The purpose of pulmonary function testing in children with asthma is to search for obstructive airway disease. We examined the charts of 169 asthmatic children during intervals between acute exacerbations. The severity of asthma was determined according to VIALATTE classification, with the Tiffeneau ration FEV1/VC (1) and the MMFR/VC ratio serving as obstructive indices. According to these data, children were classified into three groups: normal children (normal FEV1/VC and MMFR/VC), children with probable obstruction of the distal airways (normal FEV1/VC and decreased MMFR/VC), and children with both proximal and distal airway obstruction (decreased FEV1/VC and MMFR/VC). Since suggested normal values vary in the literature, we compared FEV1 and MMFR to determine as accurately as possible the number of children with obstructive disease. The relationship between the degree of clinical involvement and pulmonary function testing results was studied. Clinically, asymptomatic children with suspected normal respiratory function had evidence of obstructive disease in two out of three cases, and would benefit from drug therapy.

[Insomnia following a lesion of the paramedial preoptic area is reversible by inactivation of the posterior hypothalamus in the cat]. / L'insomnie consécutive à la lésion de la région préoptique paramédiane est réversible par inactivation de l'hypothalamus postérieur chez le chat.

The bilateral intratissular injection of muscimol, an agonist of gamma amino butyric acid (GABA), induced a transient hypersomnia (slow wave sleep and paradoxical sleep) in an insomniac cat whose paramedial preoptic area had been previously bilaterally destroyed.

[Long-duration insomnia after lesions of the perikaryons of the paramedian preoptic area in cats]. / Insomnie de longue durée après lésions des pérykarions de l'aire préoptique paramédiane chez le chat.

The destruction of paramedian preoptic neurons by intra-tissue injection of ibotenic acid induces, in the cat, the disappearance of deep slow wave sleep and paradoxical sleep for 2 to 4 weeks, while light slow wave sleep is slightly disturbed. This insomnia, well tolerated, is not secondarily associated with central temperature disturbance.