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PubMedDate not supplied

Effects of chronic toluene inhalation on avoidance conditioned behavior in rats.

Thirty-two Wistar albino rats were distributed at random in a factorial design 2 x 2, with two age groups (20 and 90 days old), and two treatments (chronically exposed to toluene vapors 30,000-40,000 ppm in air/15 minutes per day for 30 days, and controls with only air). Twenty-four hours after the last exposure, the rats were tested for conditioned behavior in a "T" maze of avoidance electric shock. Latency of initial response to escape (LIRE) and latency of escape (LE) were measured in seconds. Adult rats both exposed to chronic toluene inhalation and non-exposed showed higher values of LIRE and LE with respect young rats. Animals exposed to chronic toluene inhalation also presented higher values of latency in both LIRE and LE when compared to non-exposed to toluene (controls) of the same age. The differences were evaluated by Friedman's test. The findings are suggestive of brain dysfunction associated with chronic toluene inhalation, and may represent a delay to respond to a displeasure stimulus probably due to defect of internal mechanisms of facilitation-inhibition of neural impulses, mediated by neurotransmitters.

Animals↗

PubMed1996

NMDA-dependent modulation of CA1 local circuit inhibition.

Whole-cell and extracellular recording techniques were used to examine local circuit inhibition in the CA1 region of the rat hippocampus in vitro. Activation, primarily of the recurrent inhibitory circuit by alvear stimulation, elicited an IPSP in pyramidal neurons that was dependent, in part, on NMDA receptor activation. Application of a tetanizing stimulus to the alveus evoked long-term potentiation (LTP) of the intracellularly recorded recurrent IPSPs. This LTP also was NMDA-dependent and was more sensitive to blockade by the NMDA antagonists 2-amino-5-phosphonovalerate (APV) and N-acetyl-aspartyl-glutamate, than the excitatory LTP produced by Schaffer collateral stimulation. With regard to APV, the sensitivity of inhibitory LTP was an order of magnitude greater. A biophysical simulation of hippocampal CA1 circuitry was used in a model of learned pattern recognition that included LTP in both excitatory and inhibitory recurrent circuits. In this model, selective blockade of inhibitory LTP produced aberrant spread of lateral excitation, resulting in confusion of normally distinguishable patterns of neuronal activity. Consideration is given to the possibility that selective disruption of NMDA-dependent modulation of local circuit inhibition may serve as a model for some aspects of dysfunction associated with NMDA-antagonist exposure and schizophrenia.

2-Amino-5-phosphonovalerate↗

PubMed1996

delta-Aminolevulinic acid-induced synaptosomal Ca2+ uptake and mitochondrial permeabilization.

delta-Aminolevulinic acid (ALA) overload is thought to be responsible for the neuropsychiatric manifestations of various porphyric disorders. In fact, ALA-generated oxyradicals have been shown to cause oxidative lesions in rat brain synaptic membranes and to decrease GABAergic receptor affinity. We now describe a stimulatory effect of ALA (1 mM) on Ca2+ uptake by cortical synaptosomes and an inhibitory effect on both transmembrane potential and oxygen consumption of intrasynaptosomal mitochondria. Both effects were partly abolished by the addition of antioxidants and the mitochondrial transmembrane potential dissipation observed to be protected by 1 microM ruthenium red. Based on these data and on the synaptosomal 14C-ALA uptake capacity, we suggest that ALA causes oxidative damage to the mitochondrial membrane. These ALA properties might be involved in the neuropsychiatric porphyric manifestations since enhanced cellular Ca2+ uptake and cerebral mitochondria dysfunction seem to be associated with several neurodegenerative processes.

Aminolevulinic Acid↗

PubMed2025

Impacts of hnRNP A1 Splicing Inhibition on the Brain Remyelination Proteome.

Oligodendrocytes, the myelinating cells in the central nervous system, are implicated in several neurological disorders marked by dysfunctional RNA-binding proteins (RBPs). The present study aimed at investigating the role of hnRNP A1 in the proteome of the corpus callosum, prefrontal cortex, and hippocampus of a murine cuprizone-induced demyelination model. Right after the cuprizone insult, we administered an hnRNP A1 splicing activity inhibitor and analyzed its impact on brain remyelination by nanoESI-LC-MS/MS label-free proteomic analysis to assess the biological processes affected in these brain regions. Significant alterations in essential myelination proteins highlighted the involvement of hnRNP A1 in maintaining myelin integrity. Pathways related to sphingolipid and endocannabinoid signaling were affected, as well as the synaptic vesicle cycle and GABAergic synapses. Although behavioral impairments were not observed, molecular changes suggest potential links to memory, synaptic function, and neurotransmission processes. These findings enhance our understanding of the multifaceted roles of hnRNP A1 in the central nervous system, providing valuable insights for future investigations and therapeutic interventions in neurodegenerative and demyelinating diseases.

Animals↗

PubMed2006

Single-fiber electromyography shows terminal axon dysfunction in Miller Fisher syndrome: a case report.

We studied a patient with ophthalmoparesis and pupillary areflexia 2 weeks after a viral syndrome. Miller Fisher syndrome was suspected but GQ1b antibodies were not detected. To define neuromuscular involvement we performed electrodiagnostic studies. Single-fiber electromyography (SFEMG) in the extensor digitorum communis (EDC) showed abnormal jitter and axonal blocking, suggesting terminal axon dysfunction. Subsequent GQ1b antibody titers were elevated to borderline levels. Clinical symptoms gradually resolved. SFEMG may help characterize neuropathies associated with antibodies to neuronal ganglioside and identify involvement of the terminal axon and neuromuscular junction.

Axons↗

PubMed2003

New neurophysiology and central nervous system dysfunction.

PURPOSE OF REVIEW: The goal of this article is to summarize very recent technologic advances in neurophysiologic monitoring and to illustrate their potential benefit to critical care medicine. RECENT FINDINGS: Simplified, computer-processed electroencephalography devices now permit cost-effective, long-term critical care monitoring. They may be used alone to objectively assess sedation or coma level. In addition, these monitors serve as screening tools for more detailed electrophysiologic characterization of cortical dysfunction resulting from seizures, ischemia, or hypoxia. Somatosensory potentials broaden these capabilities to the entire neuraxis, whereas long-latency auditory evoked potentials facilitate measurement of changes in vigilance and cognition. Motor evoked potentials offer a sensitive and reliable method to determine the function of descending motor pathways in uncooperative or unresponsive patients. They may also yield a new measure of cortical excitability. New developments with transcranial Doppler ultrasonography promise noninvasive measures of cerebral perfusion pressure and particulate embolization. Near-infrared spectroscopy appears to enable noninvasive measurement of regional tissue oxygenation in both the brain and spinal cord. SUMMARY: When used together, these continuous measures of synaptic function, cerebral perfusion, and oxygenation give the clinician a vast amount of otherwise unobtainable information regarding the functional status of the central nervous system.

Central Nervous System Diseases↗

PubMed2003

The role of GABA in the pathophysiology and treatment of anxiety disorders.

Mechanisms underlying the pathological characteristics of the various anxiety disorders have yet to be fully elucidated. One of the most widely accepted mediators known to play a central role in the pathophysiology of anxiety disorders is the g-aminobutyric acid (GABA) system. Evidence supporting the role of a dysfunctional GABA system has resulted from clinical experience with the benzodiazepines, as well as subsequent determination of mechanism of action, genetic engineering, and neuroimaging studies of the GABA receptor. The concatenation of results suggests a relative deficiency in GABA neurotransmission, which can be augmented by agents acting on different components of the GABA system. Agents such as the benzodiazepines, neuroactive steroids, and barbiturates act as allosteric modulators of the GABAA receptor; b-carboline and the barbiturates function as direct GABA agonists. Valproate, gabapentin, pregabalin, and vigabatrin increase brain GABA levels or neurotransmission at least in part by targeting the metabolic pathways of GABA. Tiagabine selectively increases synaptic GABA availability by blocking the reuptake of GABA via transporter inhibition. Evidence exists, to a greater or lesser extent, that all of these agents possess anxiolytic properties, as would be expected by their mechanisms of action. This article reviews the findings implicating the GABA system in the pathophysiology of anxiety disorders and describes the potential role of agents that modulate GABA neurotransmission in the treatment of these disorders.

Anxiety Disorders↗

PubMed1995

Involvement of sigma 1 receptor in (+)-N-allylnormetazocine-stimulated hippocampal cholinergic functions in rats.

The effects of the stereoisomers of N-allylnormetazocine (SKF-10,047) on the hippocampal cholinergic functions were compared in rats. A putative sigma 1 receptor agonist, (+)-SKF-10,047, elicited an increase of hippocampal extracellular acetylcholine level and anti-amnesic effect against scopolamine-induced memory dysfunctions in rats. These phenomena were not produced by (-)-SKF-10,047, and were reversed by haloperidol, a putative sigma 1 receptor antagonist. Such stereoselectivity and antagonism imply an involvement of sigma 1 receptors in these (+)-SKF-10,047-stimulated hippocampal cholinergic functions.

Acetylcholine↗

PubMed2004

Critically timed ethanol exposure reduces GABAAR function on septal neurons developing in vivo but not in vitro.

Six-day 'binge' ethanol intoxication postnatal days (PD) 4-9 delays up-regulation of gamma-aminobutyric acid type A receptors (GABAARs) in developing rat septal neurons [Dev. Brain Res. 130 (2001) 25]. This distortion occurs during synaptogenesis and could contribute to cognitive dysfunction in fetal alcohol syndrome (FAS). Here, we asked two questions concerning requirements for vulnerability to GABAAR blunting by ethanol. First, we asked whether receptor blunting required PD 4-9 ethanol exposure in rat pups and found that just a brief 2-day exposure (PD 8-9) was as effective as all 6 days. However, 2-day exposure on PD 4-5 was ineffective, showing that 'binge' timing was important. We also asked whether 'binge' exposure directly inhibited intrinsic processes of septal neurons and could blunt GABAARs on cells maturing outside the brain. Embryonic septal neurons grown in serum-free dispersed culture developed extensive dendritic arborizations, spontaneous synaptic activity and robust whole-cell GABAAR function, but surprisingly, did not show developmental up-regulation of GABAARs like septal neurons maturing in vivo [Brain Res. 810 (1998) 100]. Furthermore, age-matched 6-day 'binge' ethanol exposure did not blunt GABAAR function in septal neurons in vitro. These results suggest developmental mechanisms driving up-regulation of GABAAR function in septal neurons in vivo briefly becomes vulnerable to ethanol insult in early postnatal life. While septal neurons express comparable functional GABAARs whether maturing in vivo or in vitro, vulnerability to ethanol-induced receptor blunting requires elements of an intact brain environment not replicated in culture.

Analysis of Variance↗

PubMedDate not supplied

Long-term potentiation in mice lacking the neural cell adhesion molecule L1.

Genetic evidence indicates that cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) are critical for activity-dependent synapse formation at the neuromuscular junction in Drosophila and have also been implicated in synaptic remodelling during learning in Aplysia (see [1] for review). In mammals, a widely adopted model for the process of learning at the cellular level is long-term potentiation (LTP) in the hippocampal formation. Studies in vitro have shown that antibodies to the IgCAMs L1 and NCAM reduce LTP in CA1 neurons of rat hippocampus, suggesting a role for these molecules in the modulation of synaptic efficacy, perhaps by regulating synaptic remodelling [2]. A role for NCAM in LTP has been confirmed in mice lacking NCAM [3] (but see [4]), but similar studies have not been reported for L1. Here we examine LTP in the hippocampus of mice lacking L1 [5,6], using different experimental protocols in three different laboratories. In tests of LTP in vitro and in vivo we found no significant differences between mutant animals and controls. Thus, contrary to expectation, our data suggest that L1 function is not necessary for the establishment or maintenance of LTP in the hippocampus. Impaired performance in spatial learning exhibited by L1 mutants may therefore not be due to hippocampal dysfunction [6].

Animals↗

PubMed2002

Impaired M-current and neuronal excitability.

PURPOSE: Benign familial neonatal convulsions (BFNC), a hereditary epilepsy, occurs specifically in newborns and remits spontaneously after this period. Several mutations of either KCNQ2 or KCNQ3, members of the KCNQ-related K+-channel (KCNQ-channel) family, were identified as a cause of BFNC. Such mutations impair KCNQ-related M- current, an element of the inhibitory system in the central nervous system (CNS), and therefore are thought to result in neuronal hyperexcitability. METHODS: To clarify the pathogenesis of BFNC, this study investigated the effects of the KCNQ channel on propagation of neuronal excitability using a 64-channel multielectrode dish (MED64) system for novel two-dimensional monitoring of evoked field potentials including fiber volley (FV) and field excitatory postsynaptic potential (fEPSP). RESULTS: Dup996, a selective KCNQ-channel inhibitor, did not affect the amplitude of FV or fEPSP, but enhanced the FV and fEPSP propagation. The gamma-aminobutyric acid (GABA)A-receptor antagonist, bicuculline, enhanced their propagation, whereas alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/glutamate-receptor antagonist, DNQX, reduced both amplitude and propagation of fEPSP without affecting those of FV. Under the condition of GABAA-receptor blockade by bicuculline, Dup996 enhanced the amplitude of fEPSP and propagation of FV and fEPSP without affecting the amplitude of FV. Dup996 enhanced the stimulating effects of bicuculline on the propagation and amplitude of FV and fEPSP, but it did not affect the inhibiting effects of DNQX. CONCLUSIONS: These results suggest that the occurrence of BFNC cannot be produced by KCNQ-channel dysfunction alone but by reciprocal action between impaired KCNQ channel and the other unknown.

Age Factors↗

PubMed1993

Brain lesions in alcoholics.

Brain lesions in alcoholics are multifactorial in origin. Ethanol neurotoxicity, Wernicke's encephalopathy, hepatocerebral degeneration, head trauma, central pontine myelinolysis, Marchiafava-Bignami syndrome, pellagra, and premorbid pathological conditions, such as fetal alcohol syndrome, may all contribute to cognitive dysfunction in alcoholics. With the exception of ethanol neurotoxicity, all of these conditions are associated with specific neuropathological lesions. Wernicke's encephalopathy, the neurological syndrome of thiamine deficiency, is frequently overlooked during life and may cause global dementia as well as the more familiar Korsakoff's amnestic syndrome. Distinguishing ethanol neurotoxicity from nutritional deficiency can be facilitated by magnetic resonance imaging, which can visualize some of the specific macroscopic lesions of Wernicke's encephalopathy, central pontine myelinolysis, cerebellar degeneration, and Marchiafava-Bignami syndrome. Computerized morphometric studies of alcoholic brains have revealed ventricular enlargement, selective loss of subcortical white matter, and alterations in neuronal size, number, architecture, and synaptic complexity. These lesions tend to be more severe when there is coexisting nutritional deficiency or liver disease, suggesting that ethanol neurotoxicity may not be the sole cause. A search for similar lesions in nonalcoholic Wernicke's encephalopathy and nonalcoholic liver disease will help determine the specificity of these lesions.

Alcohol Amnestic Disorder↗

PubMed2000

[Cognitive dysfunction in Parkinson's disease].

The neuropsychological impairments associated with Parkinson's disease(PD) have been often documented. However, the pathological mechanisms underlying cognitive dysfunction are hardly solved, as compared with motor dysfunction. Moreover, the precise relationships between the two dysfunctions have remained aloof. This paper attempts to clarify three specific domains of isolated cognitive impairments: dysexecutive syndrome, memory disturbance, and bradyphrenia, which are specifically observed in PD. It especially discusses the neuropsychological relationships between these impairments and the stages of illness. Several neuropsychological experiments to examine these three domains of cognitive impairments were conducted. Significant results were obtained in the following: set-shifting and divergent thinking were significantly impaired in both the early group and the advanced group; while set-maintaining, procedural learning, and cognitive speed, were only significantly disturbed in the advanced group. The failure to acquire procedural skills and the slowing of cognitive speed, were correlated with decreased attention of working memory in the advanced group. These results indicate that the shifting of cognitive sets maybe disturbed in the embryonic stage of the disease. The results also indicated that other cognitive dysfunctions might manifest themselves during the advanced stages due to attentional deficits. In conclusion, it is possible that other neurotransmitters maybe involved in the progressive degeneration of other systems in addition to the dopaminergic system. For example: serotoninergic, noradrenergic and cholinergic systems. Therefore, further research is required to establish which neurotransmitters are involved in their corresponding cognitive impairments in PD.

Basal Ganglia↗

PubMed1993

[Congenital myasthenia with esophageal involvement].

BACKGROUND: Mild disorders associated with persistent neonatal myasthenia gravis may not be recognized for several months. Esophageal dysfunction in this type of myasthenia has never been studied. CASE REPORT: A gastroesophageal reflux was diagnosed during the first weeks of life in a girl; she was not treated. At 8 month-old, she was admitted for febrile convulsions; the pyrexia was due to urinary tract infection by Escherichia coli. 4 days later, the infant displayed weakness of the eyelids and extraocular muscles. The proximal muscles of the arms were also weak. Neostigmine, 0.3 mg subcutaneously, completely removed the symptoms in a few minutes. Neuromuscular transmission tests showed a progressive decrease in eyelid muscle response on repetitive stimulation of the nerve, with a pattern of post-synaptic defects that was corrected by edrophonium chloride injection. Neither the girl nor her mother had acetylcholine receptor antibodies. Overnight monitoring of the distal esophagus pH showed numerous episodes of acid reflux, essentially after the meal. Manometry disclosed abnormalities of both the striated and smooth muscles of the esophagus that were corrected with neostigmine. The girl was given neostigmine and was in good condition one year later. CONCLUSION: Myasthenia could worsen and/or trigger a gastroesophageal reflux by decreasing esophageal clearance and lower esophageal sphincter pressure.

Female↗

PubMed2003

ALDH1 mRNA: presence in human dopamine neurons and decreases in substantia nigra in Parkinson's disease and in the ventral tegmental area in schizophrenia.

Dopamine (DA) neurons degenerate in Parkinson's disease and dopamine neurotransmission may be affected in psychotic states seen in schizophrenia. Understanding the regulation of enzymes involved in DA metabolism may therefore lead to new treatment strategies for these severe conditions. We investigated mRNA expression of the cytosolic aldehyde dehydrogenase (ALDH1), presumably involved in DA degradation, by in situ hybridization in DA neurons of human postmortem material. Parallel labeling for GAPDH, neuron-specific enolase, tyrosine hydroxylase, dopamine transporter, and dopamine beta-hydroxylase was used to ensure suitability of tissue specimen and to identify all dopamine neurons. ALDH1 was found to be expressed highly and specifically in DA cells of both substantia nigra (SN) and the ventral tegmental area (VTA) of controls. A marked reduction of ALDH1 expression was seen in surviving neurons of SN pars compacta but not of those in the VTA in Parkinson's disease. In patients suffering from schizophrenia we found ALDH1 expression at normal levels in DA cells of SN but at significantly reduced levels in those of the VTA. We conclude that ALDH1 is strongly and specifically expressed in human mesencephalic dopamine neurons and that low levels of ALDH1 expression correlate with DA neuron dysfunction in the two investigated human conditions.

Adult↗

PubMed2006

Redox proteomics identification of oxidatively modified hippocampal proteins in mild cognitive impairment: insights into the development of Alzheimer's disease.

Mild cognitive impairment (MCI) is generally referred to the transitional zone between normal cognitive function and early dementia or clinically probable Alzheimer's disease (AD). Oxidative stress plays a significant role in AD and is increased in the superior/middle temporal gyri of MCI subjects. Because AD involves hippocampal-resident memory dysfunction, we determined protein oxidation and identified the oxidized proteins in the hippocampi of MCI subjects. We found that protein oxidation is significantly increased in the hippocampi of MCI subjects when compared to age- and sex-matched controls. By using redox proteomics, we determined the oxidatively modified proteins in MCI hippocampus to be alpha-enolase (ENO1), glutamine synthetase (GLUL), pyruvate kinase M2 (PKM2) and peptidyl-prolyl cis/trans isomerase 1 (PIN1). The interacteome of these proteins revealed that these proteins functionally interact with SRC, hypoxia-inducible factor 1, plasminogen (PLG), MYC, tissue plasminogen activator (PLAT) and BCL2L1. Moreover, the interacteome indicates the functional involvement of energy metabolism, synaptic plasticity and mitogenesis/proliferation. Therefore, oxidative inactivation of ENO1, GLUL and PIN1 may alter these cellular processes and lead to the development of AD from MCI. We conclude that protein oxidation plays a significant role in the development of AD from MCI and that the oxidative inactivation of ENO1, GLUL, PKM2 and PIN1 is involved in the progression of AD from MCI. The current study provides a framework for future studies on the development of AD from MCI relevant to oxidative stress.

Aged↗

PubMed2005

Increased risk of Alzheimer's disease in Type II diabetes: insulin resistance of the brain or insulin-induced amyloid pathology?

Type II diabetes mellitus (DM2) is associated with an increased risk of cognitive dysfunction and dementia. The increased risk of dementia concerns both Alzheimer's disease and vascular dementia. Although some uncertainty remains into the exact pathogenesis, several mechanisms through which DM2 may affect the brain have now been identified. First, factors related to the 'metabolic syndrome', a cluster of metabolic and vascular risk factors (e.g. dyslipidaemia and hypertension) that is closely linked to DM2, may be involved. A number of these risk factors are predictors of cerebrovascular disease, accelerated cognitive decline and dementia. Secondly, hyperglycaemia may be involved, through adverse effects of potentially 'toxic' glucose metabolites on the brain and its vasculature. Thirdly, insulin itself may be involved. Insulin can directly modulate synaptic plasticity and learning and memory, and disturbances in insulin signalling pathways in the periphery and in the brain have recently been implicated in Alzheimer's disease and brain aging. Insulin also regulates the metabolism of beta-amyloid and tau, the building blocks of amyloid plaques and neurofibrillary tangles, the neuropathological hallmarks of Alzheimer's disease. In this paper, the evidence for the association between DM2 and dementia and for each of these underlying mechanisms will be reviewed, with emphasis on the role of insulin itself.

Alzheimer Disease↗

PubMed2001

Mechanisms of axonal dysfunction after spinal cord injury: with an emphasis on the role of voltage-gated potassium channels.

Dysfunction of surviving axons which traverse the site of spinal cord injury (SCI) appears to contribute to posttraumatic neurological deficits, though the underlying mechanisms remain unclear. Although demyelination of injured but surviving axons following trauma appear to be a major contributor of axonal conduction deficits, altered activity of ion channels may also play an important role. It has been theorized that exposure of K+ channels as a result of demyelination would result in a reduced safety factor of action potential propagation across the demyelinated region of the axon. This theory and electrophysiological studies using K+ channel blockers on animal nerve preparations prompted the investigation of 4-aminopyridine (4-AP), a blocker of rapidly activating voltage-gated K+ channels, as a therapeutic agent in both multiple sclerosis and spinal cord injured patients. Several preliminary clinical trials have already demonstrated therapeutic benefit of 4-AP in both multiple sclerosis and spinal cord injured patients. In this review, we shall give a comprehensive summary of the mechanisms of axonal dysfunction following SCI and how axonal dysfunction may have resulted due to specific pathological changes following trauma including the ultrastructural and molecular changes that occur to myelinated axons. The pathology of spinal cord injury is very complex and many different mechanisms may contribute to axonal conduction deficits and the associated sensory and motor loss.

4-Aminopyridine↗