Focal brain hyperthermia. I. The cerebellar cortex

Focal brain hyperthermic methodology has been described and data presented on the cerebellum which show that enhancement of electrical activity of cerebellar cortex occurs when this method is used with careful monitoring of temperature. The duration of electrically induced cerebral after-discharges is shortened when cerebellar warming reaches 39.5--42.0 degrees C,. Since these effects are repeatable over many hours, there appears to be little, if any, resultant damage. Such induced changes in the cerebrum resemble those previously reported in which electrical stimuli were applied to the cerebellar cortex.     

Regional distribution of lactate dehydrogenase isoenzymes in adult rat brain.

The highest lactate dehydrogenase (LDH) activity was found in thalamus, statistically significantly less in cerebral and cerebellar cortex and the lowest in pons. LDH1 and LDH4+5 represented 58% and 23% of the total activity in cerebral cortex, 54% and 20% in thalamus, 42% and 4% in cerebellar cortex and 55% and 7% in pons, respectively.     

Topische Bestimmung des zerebralen Angriffs von Reserpin (Serpasil)

Summary The impact of Reserpine (Serpasil) has been investigated by stimulating different parts of the rabbit's brain (Cortex, Diencephalon, Rhinencephalon,Subst. reticularis). Simultaneously the spontaneous brain activity and the electrically induced discharge have been recorded and studied in the cortex, the thalamus (Nucl. dors. med. andlat.), the rhinencephalon and theSubst. reticularis of the brain stem.Reserpine has a depressing influence on the diencephalo-cortical system. It raises the threshold of the afterdischarge induced by stimulation of the cortex and of the thalamus.Nevertheless the drug induces no electrographic sleep pattern. It maintains a steady electric pattern of alertness and increases the electrical ground activity of the rhinencephalon.Reserpine also depresses the spikes induced in the cortex and in the thalamus by stimulation of the pontobulbar reticular system. This effect is supposed to be due to a pharmacological action located at the thalamocortical level rather than in the bulbar segment of the arousal system.     

Effect of harmaline on the cerebello-rubral system

Summary Harmaline induces synchronous rhythms in both the cerebellum and the red nucleus of the rabbit. The level of synchronization is lower in the red nucleus than in the cerebellar cortex, probably because the cerebello-rubral pathway and the red nucleus neurons only participate poorly in the harmaline-induced olivo-cerebellar rhythm.Acknowledgments. We thank Mrs M. Satzinger and Mrs A. Motejlek for their technical assistance. The drugs were generously supplied by Bayer Pharma GmbH, Vienna (Evipan^® and Epontol^®), Boehringer, C. H. Sohn, Ingelheim am Rhein, Federal Republic of Germany (Flaxedil^®) and Hoffmann-La Roche GmbH, Vienna (harmaline hydrochloride).     

The effect of unilateral cerebellar pedunculotomy on the vascular development of the neonatal rat cerebellum

After cerebellar pedunculotomy the density of the blood vessel network in the cerebellar cortex was not different from that in the control animals. But the pattern of the blood vessels was different, being less organized in the operated animals.     

Action d'un inhibiteur de la carboanhydrase,l'acétazolamide,sur l'excitabilité du cortex,du thalamus et du rhinencéphale

Summary The electrical activity induced by stimulation of the cortex, diencephalon and rhinencephalon was studied in the rabbit under the influence of a carbonic anhydrase inhibitor, acetazolamide or Diamox. A significant decrease of the excitability was found in the diencephalon.The rapidity and the electivity of this action, as well as the blood pH variations simultaneously registered, suggest a specific inhibition of cerebral carbonic anhydrase by Diamox, although a participation of the metabolic acidosis cannot be fully excluded.     

Ethanol impairs Rho GTPase signaling and differentiation of cerebellar granule neurons in a rodent model of fetal alcohol syndrome

Developmental exposure to ethanol impairs fetal brain development and causes fetal alcohol syndrome. Although the cerebellum is one of the most alcohol-sensitive brain areas, signaling mechanisms underlying the deleterious effects of ethanol on developing cerebellar granule neurons (CGNs) are largely unknown. Here we describe the effects of in vivo ethanol exposure on neurite formation in CGNs and on the activation of Rho GTPases (RhoA and Rac1), regulators of neurite formation. Exposure of 7-day-old rat pups to ethanol for 3 h moderately increased blood alcohol concentration (BAC) (∼40 mM) and inhibited neurite formation and Rac1 activation in CGNs. Longer exposure to ethanol for 5 h resulted in higher BAC (∼80 mM), induced apoptosis, inhibited Rac1, and activated RhoA. Studies demonstrated a regulatory role of Rho GTPases in differentiation of cerebellar neurons, and indicated that ethanol-associated impairment of Rho GTPase signaling might contribute to brain defects observed in fetal alcohol syndrome. Received 16 July 2006; received after revision 12 September 2006; accepted 13 October 2006     

Are the pores of intramembrane particles of postsynaptic membrane transmitter-dependent channels?

The rat neonatal cerebellar cortex has been studied using the freeze fracture technique. In the dendritic postsynaptic membrane, intramembrane particles containing an electron-dense central area have been detected. This type of area could be a platinum aggregate within a channel which, crossing the particle, may connect the postsynaptic cytoplasm with the synaptic cleft.     

‘Binding’ of glycine andγ-aminobutyric acid to synaptosomal fractions of 6 regions of the feline brain; effects of strychnine

Summary GABA (6×10^–6 M) binding to synaptosome-enriched fractions of cat CNS exhibited a clear rostro-caudal gradient, whereas glycine (6×10^–6 M) binding was greatest to particles of cerebellar cortex, and this was followed by medulla caudate nucleus cerebral cortex pons > corona radiata. Strychnine-SO₄ (10^–3 or 10^–4 M) inhibited the binding of GABA and glycine in all brain regions studied; at 10^–5 M this drug inhibited the binding of both GABA and glycine only to particles of the cerebral cortex.This study was supported by Centro Nacional Ramón y Cajal and Fundación Juan March. P. M. was a summer student from Eastern Nazarene College, Wollaston, Mass., USA.     

D-ala2-Metenkephalinamide blocks the synaptically elicited cortical spreading depression in rats

Summary Spreading depression (SD) was elicited in rats anesthetized with pentobarbital by a train of 8 electrical pulses (0.1 ms, 10 Hz) applied to parietal cortex. Local application of 50 g of D-ala²-metenkephalinamide (DAME) on the stimulated area evoked one or two SD waves followed by an increase of SD threshold from 40 V to 90 V. This effect could be partly prevented by naloxone (1 mg/kg i.p.) and reversed by local application of 4-aminopyridine (10^–3 M, 2 l), which reduced SD threshold to 5 and 20 V in normal and DAME-treated cortex, respectively. It is argued that DAME exerts an inhibitory effect on cortical neurons and that the initial SD facilitation is due to initial blockade of inhibitory neurons in the superficial cortical layers.supported by the European Training Program in Brain and Behavior Research.     

Contribution à l'étude d'une propriété répétitive du cerveau

Summary While pursuing the study of cortical functioning by the EEG. and after-image methods, we have come to believe that every stimulation evokes in the corresponding area of the cortex not only a simultaneous excitation but also acontinued action, i.e. after stimulation, several successive excitations of progressively diminishing intensity appear in the same area of the cortex.We have investigated the continued groups appearing on corticographical tracings taken from different cortical areas of the experimental animal (the rabbit) after various forms of stimulation (auditory, electrical, and visual). By comparing them with the after-images seen by human subjects in EEG. experiments, we have been led to identify the two phenomena.In order to carry this study further, we have undertaken two series of corticographical experiments, recording tracings takensimultaneously from the parietal and striate areas of the rabbit. The first series was intended to study the effects on the tracings of visual stimuli. The second was concerned with the effects on the same tracings of weak electrical stimuli.

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Nous avons consacré à cette propriété répétitive du cerveau une note parue dans les Comptesrendus de l'Académie des Sciences, Juillet 1955, Paris — dont le présent article constitue le développement.     

Glutamine synthetase activity during mouse brain development

The specific activity of glutamine synthetase (GS) in mouse brain was 2-fold higher in the olfactory bulbs than in other regions. After birth, the specific activity of GS increased more rapidly in medulla oblongata and in olfactory bulbs, than in cerebral and cerebellar cortex. The activity of GS in primary cultures of brain hemispheres increased more slowly than in homogenates of whole brains. However, when astroblasts were treated in vitro with glucocorticoids or mouse brain extracts, GS activity reached 4 times the level measured in the homogenate of an adult mouse brain. We conclude that levels of GS activity may relate to the maturation of astrocytes, and propose that GS may be used as a marker of astrocytic maturation.     

Glutamine synthetase activity during mouse brain development

Summary The specific activity of glutamine synthetase (GS) in mouse brain was 2-fold higher in the olfactory bulbs than in other regions. After birth, the specific activity of GS increased more rapidly in medulla oblongata and in olfactory bulbs, than in cerebral and cerebellar cortex. The activity of GS in primary cultures of brain hemispheres increased more slowly than in homogenates of whole brains. However, when astroblasts were treated in vitro with glucocorticoids or mouse brain extracts, GS activity reached 4 times the level measured in the homogenate of an adult mouse brain. We conclude that levels of GS activity may relate to the maturation of astrocytes, and propose that GS may be used as a marker of astrocytic maturation.     

Voltage-gated sodium currents in cerebellar Purkinje neurons: functional and molecular diversity

Purkinje neurons, the sole output of the cerebellar cortex, deliver GABA-mediated inhibition to the deep cerebellar nuclei. To subserve this critical function, Purkinje neurons fire repetitively, and at high frequencies, features that have been linked to the unique properties of the voltage-gated sodium (Nav) channels expressed. In addition to the rapidly activating and inactivating, or transient, component of the Nav current (I_NaT) present in many types of central and peripheral neurons, Purkinje neurons, also expresses persistent (I_NaP) and resurgent (I_NaR) Nav currents. Considerable progress has been made in detailing the biophysical properties and identifying the molecular determinants of these discrete Nav current components, as well as defining their roles in the regulation of Purkinje neuron excitability. Here, we review this important work and highlight the remaining questions about the molecular mechanisms controlling the expression and the functioning of Nav currents in Purkinje neurons. We also discuss the impact of the dynamic regulation of Nav currents on the functioning of individual Purkinje neurons and cerebellar circuits.     

Presence of giant mitochondria during cerebellar ontogenesis in reptiles

Summary Giant mitochondria were observed in the perikarya and dendrites of Purkinje cells in the developing cerebellar cortex of the lizardGallotia galloti at sevral stages previous to hatching. Such mitochondria are absent from the adult cerebellum.4 December 1986The authors would like to thank Prof. L. Puelles (Murcia University) for his critical assistance and the Edafology Department of La Laguna University for facilities offered, specially for the use of the electron microscope. This work has been pertially suported by a CAICYT research grant No. 909-2.     

Organization of the mammalian red nucleus and its interconnections with the cerebellum.

The red nucleus in monkeys and rats consists of a magnocellular, rubrospinal portion which receives its cerebellar information from the nucleus interpositus, and a parvocellular, rubroolivary portion which receives cerebellar afferents from the nucleus lateralis. Distinct interpositorubrospinal and dentatorubroolivary projections are therefore common to these 2 species.     

Wasting syndrome in neonatal mice after administration of salivary gland homogenate

Summary A wasting syndrome, similar to that occurring after cortisol treatment, was induced in neonatal mice by means of the daily i.p. administration of salivary gland homogenate: 24 h after a single injection of the, homogenate, profuse cell necrosis was observed in the thymic cortex, 48 h later the cortex was devoid of lymphocytes. It is hypothesized that the submandibular glands of mice contain substance which are capable of inducing a cortisol-like effect.We should like to thank Miss Angela Würfler for her careful technical assistance.     

ACTH-Stimulierung der Corticosteroidbiosynthese durch Freisetzung «gebundener» 21-Desoxypregnene

Summary Impairment of 21-hydroxylation was observed when 4-C¹⁴-cholesterol was transformed into 4-C¹⁴-corticosteroids in slices of bovine adrenal cortex, whereas corticosteroid synthesis from 4-C¹⁴-progesterone proceeded freely. ACTH stimulated corticosteroid formation from 4-C¹⁴-cholesterol but not from 4-C¹⁴-progesterone. It is therefore suggested that ACTH facilitates the «release» of 21-desoxypregnenes, which are present in a «bound» form after synthesis from cholesterol in intact adrenocortical tissue, and which are unavailable for the following reactions without conditioning by ACTH.     

Intrathalamic sensory connections mediated by the thalamic reticular nucleus

The thalamus and cerebral cortex are linked together to form a vast network of interconnections. Different modes of interactions among the cells in this network underlie different states of consciousness, such as wakefulness and sleep. Interposed between the dorsal thalamus and cortex are the GABAergic neurons of the thalamic reticular nucleus (TRN), which play a pivotal role not only in switching between the awake and sleep states but also in sensory processing during the awake state. The visual, somatosensory, and auditory sectors of TRN share many of the same organizational features. Each of these sectors contains maps, which are related to its inputs and outputs, and organizational components called ‘slabs.’ It is proposed that, during wakefulness, TRN is crucially involved in resetting the activity levels in sensory nuclei of the dorsal thalamus, which allows the cortex to actively and periodically compare its on-going sensory processing with the available sensory information. Received 11 May 1999; received after revision 15 July 1999; accepted 21 July 1999     

Neuritic plaque-like structures in the rat cerebellum following prolonged alcohol consumption

Primitive neuritic plaques were observed in the inner third of the molecular layer of the cerebellar cortex of rats following chronic alcohol consumption. Neurites were identified as dystrophic parallel fiber boutons. Amyloid material dispersed among neurites was not clearly recognized, dystrophic some fibrils were frequently seen among them. Astrocytic processes were noted in the periphery of the plaque. Microglial reaction, however, was non-existent. The rarity of these lesions in the rat cerebellum and their probable relation to long periods of alcohol consumption is discussed.