Role Of Neurophysiology Research Articles

14-3-3θ is a Binding Partner of Rat Eag1 Potassium Channels

The ether-à-go-go (Eag) potassium (K+) channel belongs to the superfamily of voltage-gated K+ channel. In mammals, the expression of Eag channels is neuron-specific but their neurophysiological role remains obscure. We have applied the yeast two-hybrid screening system to identify rat Eag1 (rEag1)-interacting proteins from a rat brain cDNA library. One of the clones we identified was 14-3-3θ, which belongs to a family of small acidic protein abundantly expressed in the brain. Data from in vitro yeast two-hybrid and GST pull-down assays suggested that the direct association with 14-3-3θ was mediated by both the N- and the C-termini of rEag1. Co-precipitation of the two proteins was confirmed in both heterologous HEK293T cells and native hippocampal neurons. Electrophysiological studies showed that over-expression of 14-3-3θ led to a sizable suppression of rEag1 K+ currents with no apparent alteration of the steady-state voltage dependence and gating kinetics. Furthermore, co-expression with 14-3-3θ failed to affect the total protein level, membrane trafficking, and single channel conductance of rEag1, implying that 14-3-3θ binding may render a fraction of the channel locked in a non-conducting state. Together these data suggest that 14-3-3θ is a binding partner of rEag1 and may modulate the functional expression of the K+ channel in neurons.

A Study of GABA in Bivalve Molluscs

The nervous systems of most studied bivalves contain serotonin and dopamine in their ganglia that serve as neurotransmitters regulating various physiological functions such as heart rate, foot movement, reproduction and gill lateral cilia beating. GABA is a major inhibitory neurotransmitter found in the CNS of vertebrates and ganglia of many invertebrates. Its presence and functions have not been well studied in bivalves. Here we used a HPLC method with pre‐column derivatization and fluorescence detection to look for GABA in ganglia of Crassostrea virginica, Mercenaria mercenaria and Mytilus edulis. We also examined effects of GABA on beating of gill lateral cilia in C. virginica and M. edulis. GABA was detected in low ng amounts in each ganglia of each of the bivalves. In C. virginica and M. edulis GABA had no direct effect on lateral cilia activity when applied directly to the gill. However, when serotonin was applied to the cerebral ganglia, GABA, whether applied before or after serotonin, blocked the normal excitatory response of serotonin on the beating of the cilia. Furthermore, the GABA antagonist bicuculline methchloride blocked the effects of GABA in the cerebral ganglia of C. virginica. This study is showing that GABA is present and has a neurophysiological role in bivalve ganglia. This work was supported by grants 2R25GM0600309 of NIGMS, 0516041071 of NYSDOE and 0622197 of NSF.

The role of clinical neurophysiology in urogynecology

Clinical neurophysiological methods remain interesting research tools in urogynecology; their diagnostic role in the individual "pelvic floor" patient is, however, minor. The methods are diagnostically useful particularly in patients suspected to have a lesion involving the sphincters or the peripheral sacral nervous system, the diagnosis of which will influence management decisions or have prognostic or medicolegal relevance. Most helpful tests are the concentric needle EMG and bulbocavernosus reflex testing.

P12.8 The role of interventional neurophysiology in chronic pudendal nerve stimulation for neurogenic overactive bladder as predictive factor of success

P12.8 The role of interventional neurophysiology in chronic pudendal nerve stimulation for neurogenic overactive bladder as predictive factor of success

Clinical Neurophysiology in Alzheimer′s Disease

The pathophysiological mechanisms underlying normal aging and neurodegenerative disorders such as Alzheimer's disease (AD) have yet to be fully established. Early recognition of mild cognitive impairment (MCI) and AD requests the identification of biomarkers capable of distinguishing individuals with prodromes from healthy aging adults. Physiological brain aging is characterized by a loss of synaptic contacts and neuronal apoptosis even though neural redundancy as well as functional and structural plastic remodelling of brain networking promotes maintenance of brain activity in healthy elderly for everyday life. It is, then, important to implement techniques that are able to measure changes in normal aging brain and to discriminate them from neurodegenerative processes. As oscillatory electromagnetic brain activity is a hallmark of neuronal network function in various brain regions, an integrated approach utilizing modern neurophysiological techniques, including electroencephalography (EEG), event-related potentials (ERPs), and transcranial magnetic stimulation (TMS), together with biological markers and structural and functional imaging are promising for large-scale, affordable, and noninvasive evaluation of at-risk populations both at a group- and probably also at single-subject level. This special issue contains a series of cutting-edge articles that provides innovative information and deal with the broad issue of the role of neurophysiology for the assessment of normal aging and dementia. Of necessity, these articles focus on selected topics but the mixture of novel contributions as well as review papers on EEG, TMS and ERP provide an overview and an insight into current areas of debate. The first review of this special issue by G. Rodriguez et al., addresses an overview on the usefulness to study brain functional networks in the attempt to find noninvasive biomarkers of dementia; the second one, by R. Lizio et al., focuses on the role of modern EEG and on the possibility of combining its use together with biological and neuropsychological markers and structural and functional imaging for a low-cost, noninvasive, and widely available assessment of groups of individuals at-risk. Following these reviews, new EEG data are presented in the papers written by J. Dauwels et al. and F. Vecchio and C. Babiloni, dealing with the slowing and loss of complexity of EEG in AD patients and with the usefulness of EEG direction information flow in both AD and MCI patients, respectively. The subsequent three papers address EEG methodological issues, focusing on aspects helpful to better diagnose the AD: L.R. Trambaiolli et al. discuss in depth the possibility that EEG montage can influence AD diagnosis, F.B. Vialatte et al. provide suggestions on procedures to make EEG more specific in diagnosis, and K. van der Hiele et al. discuss the potential usefulness of electromyography in supporting the diagnosis of the disease. Then two review papers by F. Vecchio and S. Maatta and by A. Guerra et al., focus, respectively on the possibility to use auditory ERPs as well as TMS in complementing AD diagnosis, staging, and followup. The tenth study, by P. Julkunen et al., combines transcranial magnetic stimulation and electroencephalography (TMS-EEG) to assess the severity of AD. Finally, two case reports are presented, in which neurophysiology plays a central role in supporting the diagnosis of dementia with particular attention to corticobasal loss of functionality (F. Mastrolilli et al.) and possible cooccurrence of nonconvulsive seizures and dementia (C. Campana et al.). As a corollary, the last contribution by L. Valeriani reports some considerations on the actual need in the management of AD patients in emergency departments. Florinda Ferreri Sara Maatta Fabrizio Vecchio Giuseppe Curcio Fabio Ferrarelli

Augmented currents of an HCN2 variant in patients with febrile seizure syndromes

The genetic architecture of common epilepsies is largely unknown. HCNs are excellent epilepsy candidate genes because of their fundamental neurophysiological roles. Screening in subjects with febrile seizures and genetic epilepsy with febrile seizures plus revealed that 2.4% carried a common triple proline deletion (delPPP) in HCN2 that was seen in only 0.2% of blood bank controls. Currents generated by mutant HCN2 channels were approximately 35% larger than those of controls; an effect revealed using automated electrophysiology and an appropriately powered sample size. This is the first association of HCN2 and familial epilepsy, demonstrating gain of function of HCN2 current as a potential contributor to polygenic epilepsy.

FMRFamide-like peptides in root knot nematodes and their potential role in nematode physiology

FMRFamide-like peptides (FLPs) are a diverse group of neuropeptides that are expressed abundantly in nematodes. They exert potent physiological effects on locomotory, feeding and reproductive musculature and also act as neuromodulators. However, little is known about the specific expression patterns and functions of individual peptides. The current study employed rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) to characterize flp genes from infective juveniles of the root knot nematodes, Meloidogyne incognita and Meloidogyne minor. The peptides identified from these transcripts are sequelogs of FLPs from the free-living nematode, Caenorhabditis elegans; the genes have therefore been designated as Mi-flp-1, Mi-flp-7, Mi-flp-12, Mm-flp-12 and Mi-flp-14. Mi-flp-1 encodes five FLPs with the common C-terminal moiety, NFLRFamide. Mi-flp-7 encodes two copies of APLDRSALVRFamide and APLDRAAMVRFamide and one copy of APFDRSSMVRFamide. Mi-flp-12 and Mm-flp-12 encode the novel peptide KNNKFEFIRFamide (a longer version of RNKFEFIRFamide found in C. elegans). Mi-flp-14 encodes a single copy of KHEYLRFamide (commonly known as AF2 and regarded as the most abundant nematode FLP), and a single copy of the novel peptide KHEFVRFamide. These FLPs share a high degree of conservation between Meloidogyne species and nematodes from other clades, including those of humans and animals, perhaps suggesting a common neurophysiological role which may be exploited by novel drugs. FLP immunoreactivity was observed for the first time in Meloidogyne, in the circumpharyngeal nerve ring, pharyngeal nerves and ventral nerve cord. Additionally, in situ hybridization revealed Mi-flp-12 expression in an RIR-like neuron and Mi-flp-14 expression in SMB-like neurons, respectively. These localizations imply physiological roles for FLP-12 and FLP-14 peptides, including locomotion and sensory perception.

Functional consequences of mutations in the Drosophila histamine receptor HCLB

The gene hclB encodes a histamine-gated chloride channel subunit in Drosophila melanogaster. Mutations in hclB lead to defects in the visual system and altered sensitivity to the action of ivermectin. To investigate whether this member of the Cys-loop receptors is common across the Insecta, we analysed the genomes of seven other insect species (Diptera, Hymenoptera, Coleoptera) and revealed orthologues of hclB in all of them. Sequence comparisons showed high identity levels between the orthologues, indicating similar constraints and conserved function between the species. Two D. melanogaster mutants, hclBT1 (P293S) and hclBT2 (W111*, a null mutation) were tested for the lapse into, and recovery from, paralysis induced by high temperature or the anaesthetic action of halothane. At 41°C, the hclBT2 flies lapsed into coma faster than wild-type or the hclBT1 flies, while both mutants recovered more slowly. A substantially impaired recovery rate was also observed in hclBT1 after anaesthesia with halothane. Enhanced synaptic signalling at low-intensity light stimuli was registered on electroretinograms recorded from the two mutant strains. Our results suggest that HCLB may play an essential and conserved role in insect neurophysiology.

Thiamin diphosphate in biological chemistry: new aspects of thiamin metabolism, especially triphosphate derivatives acting other than as cofactors

Prokaryotes, yeasts and plants synthesize thiamin (vitamin B1) via complex pathways. Animal cells capture the vitamin through specific high-affinity transporters essential for internal thiamin homeostasis. Inside the cells, thiamin is phosphorylated to higher phosphate derivatives. Thiamin diphosphate (ThDP) is the best-known thiamin compound because of its role as an enzymatic cofactor. However, in addition to ThDP, at least three other thiamin phosphates occur naturally in most cells: thiamin monophosphate, thiamin triphosphate (ThTP) and the recently discovered adenosine thiamin triphosphate. It has been suggested that ThTP has a specific neurophysiological role, but recent data favor a much more basic metabolic function. During amino acid starvation, Escherichia coli accumulate ThTP, possibly acting as a signal involved in the adaptation of the bacteria to changing nutritional conditions. In animal cells, ThTP can phosphorylate some proteins, but the physiological significance of this mechanism remains unknown. Adenosine thiamin triphosphate, recently discovered in E. coli, accumulates during carbon starvation and might act as an alarmone. Among the proteins involved in thiamin metabolism, thiamin transporters, thiamin pyrophosphokinase and a soluble 25-kDa thiamin triphosphatase have been characterized at the molecular level, in contrast to thiamin mono- and diphosphatases whose specificities remain to be proven. A soluble enzyme catalyzing the synthesis of adenosine thiamin triphosphate from ThDP and ADP or ATP has been partially characterized in E. coli, but the mechanism of ThTP synthesis remains elusive. The data reviewed here illustrate the complexity of thiamin biochemistry, which is not restricted to the cofactor role of ThDP.

Neue Überlegungen zur klinisch-neurophysiologischen Diagnostik der ALS. Die „Awaji-Kriterien”

In December 2006 an expert group of EMG and ALS specialists met in Awaji Island, Japan, to reconsider the role of clinical neurophysiology in the diagnosis of ALS. First, the importance of conventional electromyography and electroneurography was confirmed. Furthermore, it was recommended that electromyographical signs of denervation should be regarded as being equivalent to clinical signs.It was also recommended that fasciculation potentials in the clinical setting of an ALS should be regarded as an indication of active denervation similarly to positive waves and fibrillation potentials. The special diagnostic impact of unstable motor unit potentials was stressed. In summary, these considerations would render the diagnostic category of “laboratory-supported probable ALS” superfluous. Concerning the involvement of the upper motoneuron, the experts’ opinion was that further studies to evaluate new variations of transcranial magnetic stimulation such as the triple-stimulation technique are necessary.

Phylogenetics and the correlates of mammalian sleep: A reappraisal

The correlates of mammalian sleep have been investigated previously in at least eight comparative studies in an effort to illuminate the functions of sleep. However, all of these univariate analyses treated each species, or taxonomic Family, as a statistically independent unit, which is invalid due to the phylogenetic relationships among species. Here, we reassess these influential correlates of mammalian sleep using the formal phylogenetic framework of independent contrasts. After controlling for phylogeny using this procedure, the interpretation of many of the correlates changed. For instance, and contrary to previous studies, we found interspecific support for a neurophysiological role for rapid-eye-movement sleep, such as memory consolidation. Also in contrast to previous studies, we did not find comparative support for an energy conservation function for slow-wave sleep. Thus, the incorporation of a phylogenetic control into comparative analyses of sleep yields meaningful differences that affect our understanding of why we sleep.

Differential localization of rat Eag1 and Eag2 potassium channels in the retina

Despite of their wide expression in the brain, the precise neurophysiological role of rat Eag1 (rEag1) and Eag2 (rEag2) K + channels remains elusive. Our previous studies in hippocampal pyramidal neurons demonstrate a somatodendritic localization of rEag1 and rEag2 channels, suggesting that the two channel isoforms may contribute to setting the membrane excitability of somas and dendrites. Here, we aim to further characterize the cellular and subcellular localization patterns of rEag1 and rEag2 proteins by studying their laminar distribution in the retina. Confocal microscopic analyses of immunofluorescence data revealed that rEag1 and rEag2 K + channels exhibit distinct cellular expression pattern in the retina. rEag1 immunoreactivity was most prominent in the outer half of the inner plexiform layer, whereas strong rEag2 immunostain was found in the outer and inner segments of photoreceptor cells, the outer plexiform layer, and the inner nuclear layer. These results suggest that rEag1 and rEag2 K + channels may play a significant role in the transmission of electrical signals along the retinal neuronal circuits. We also performed double-labeling experiments to demonstrate that rEag1 and rEag2 are predominantly expressed in the somatodendritic compartment of retinal neurons. In addition, we presented evidence suggesting that rEag1 channels may be expressed in the GABAergic amacrine cell. Finally, based on their different immunostaining patterns over the inner region of the retina, we propose that compared to rEag2, rEag1 expression encompasses a significantly broader range of the somatodendritic compartment of the retinal ganglion cell.

Role of neurophysiology in the clinical practice of primary pediatric headaches

AbstractThe role of electrophysiological studies in pediatric headaches is controversial. In childhood headaches, neurophysiological examinations are of interest for potential clinical use because they are noninvasive and are scarcely influenced by environmental factors or drug use. Electrophysiological studies in childhood headache principally explored the role of electroencephalographic (EEG) evaluations in migraine, while less evidence has been reported about other neurophysiological techniques, such as evoked potentials, event‐related potentials, and, less often, transcranial magnetic stimulation. In this brief review, we point out our attention to the aid of neurophysiological methods in the clinical diagnosis of pediatric headaches. Although many examinations are actually of little value in the clinical setting, they may have a potential role in some clinical subgroups or in monitoring and evaluating the effects of pharmacological treatment. Drug Dev Res 68:389–396, 2007. © 2008 Wiley‐Liss, Inc.

ApoER2 expression increases Aβ production while decreasing Amyloid Precursor Protein (APP) endocytosis: Possible role in the partitioning of APP into lipid rafts and in the regulation of γ-secretase activity

BackgroundThe generation of the amyloid-β peptide (Aβ) through the proteolytic processing of the amyloid precursor protein (APP) is a central event in the pathogenesis of Alzheimer's disease (AD). Recent studies highlight APP endocytosis and localization to lipid rafts as important events favoring amyloidogenic processing. However, the precise mechanisms underlying these events are poorly understood. ApoER2 is a member of the low density lipoprotein receptor (LDL-R) family exhibiting slow endocytosis rate and a significant association with lipid rafts. Despite the important neurophysiological roles described for ApoER2, little is known regarding how ApoER2 regulates APP trafficking and processing.ResultsHere, we demonstrate that ApoER2 physically interacts and co-localizes with APP. Remarkably, we found that ApoER2 increases cell surface APP levels and APP association with lipid rafts. The increase of cell surface APP requires the presence of ApoER2 cytoplasmic domain and is a result of decreased APP internalization rate. Unexpectedly, ApoER2 expression correlated with a significant increase in Aβ production and reduced levels of APP-CTFs. The increased Aβ production was dependent on the integrity of the NPxY endocytosis motif of ApoER2. We also found that expression of ApoER2 increased APP association with lipid rafts and increased γ-secretase activity, both of which might contribute to increased Aβ production.ConclusionThese findings show that ApoER2 negatively affects APP internalization. However, ApoER2 expression stimulates Aβ production by shifting the proportion of APP from the non-rafts to the raft membrane domains, thereby promoting β-secretase and γ-secretase mediated amyloidogenic processing and also by incrementing the activity of γ-secretase.

The Endomorphin System and Its Evolving Neurophysiological Role

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two endogenous opioid peptides with high affinity and remarkable selectivity for the mu-opioid receptor. The neuroanatomical distribution of endomorphins reflects their potential endogenous role in many major physiological processes, which include perception of pain, responses related to stress, and complex functions such as reward, arousal, and vigilance, as well as autonomic, cognitive, neuroendocrine, and limbic homeostasis. In this review we discuss the biological effects of endomorphin-1 and endomorphin-2 in relation to their distribution in the central and peripheral nervous systems. We describe the relationship between these two mu-opioid receptor-selective peptides and endogenous neurohormones and neurotransmitters. We also evaluate the role of endomorphins from the physiological point of view and report selectively on the most important findings in their pharmacology.

CAP, epilepsy and motor events during sleep: the unifying role of arousal

Arousal systems play a topical neurophysiologic role in protecting and tailoring sleep duration and depth. When they appear in NREM sleep, arousal responses are not limited to a single EEG pattern but are part of a continuous spectrum of EEG modifications ranging from high-voltage slow rhythms to low amplitude fast activities. The hierarchic features of arousal responses are reflected in the phase A subtypes of CAP (cyclic alternating pattern) including both slow arousals (dominated by the <1Hz oscillation) and fast arousals (ASDA arousals). CAP is an infraslow oscillation with a periodicity of 20-40s that participates in the dynamic organization of sleep and in the activation of motor events. Physiologic, paraphysiologic and pathologic motor activities during NREM sleep are always associated with a stereotyped arousal pattern characterized by an initial increase in EEG delta power and heart rate, followed by a progressive activation of faster EEG frequencies. These findings suggest that motor patterns are already written in the brain codes (central pattern generators) embraced with an automatic sequence of EEG-vegetative events, but require a certain degree of activation (arousal) to become visibly apparent. Arousal can appear either spontaneously or be elicited by internal (epileptic burst) or external (noise, respiratory disturbance) stimuli. Whether the outcome is a physiologic movement, a muscle jerk or a major epileptic attack will depend on a number of ongoing factors (sleep stage, delta power, neuro-motor network) but all events share the common trait of arousal-activated phenomena.

Role of intraoperative neurophysiology in primary surgery for obstetrical brachial plexus palsy (OBPP)

Management of conducting neuroma-in-continuity in primary surgery for obstetrical brachial plexus palsy (OBPP) is still discussed controversially. We present our experience with intraoperative neurophysiological recordings in the management of lesions in continuity in OBPP. A series of ten children with lesions in continuity of the upper brachial plexus is presented. Due to recordable compound nerve action potentials (CNAPs) and muscle response to motor stimulation across the neuroma, five children underwent external neurolysis of neuroma only (neurolysis group). Due to lack of recordable CNAPs or muscle response, resection of neuroma and interpositional nerve grafting were performed in another five children (resection and grafting group). Functional recovery after at least 30 months of follow-up was assessed. There was a marked difference in functional recovery between the neurolysis and the resection and grafting group. Especially, recovery of shoulder function was disappointing after external neurolysis of conducting neuroma-in-continuity. At the end of follow-up, results of shoulder and elbow function after resection of neuroma followed by interpositional nerve grafting were better without exception. Intraoperative neurophysiological recordings face certain difficulties when used in small children with OBPP. Due to overoptimistic assessment of prognosis after intraoperative CNAP recordings and motor stimulation, the functional results after neurolysis of conducting neuroma-in-continuity are disappointing. Resection of neuroma-in-continuity, conducting or not, offers the best opportunity for maximal functional recovery of the compromised upper limb in OBPP. The role of intraoperative neurophysiological techniques should be confined to the diagnosis of root avulsions.

Microelectrode array studies of basal and potassium‐evoked release of l‐glutamate in the anesthetized rat brain

L-glutamate (Glu) is the predominant excitatory neurotransmitter in the mammalian central nervous system. It plays major roles in normal neurophysiology and many brain disorders by binding to membrane-bound Glu receptors. To overcome the spatial and temporal limitations encountered in previous in vivo extracellular Glu studies, we employed enzyme-coated microelectrode arrays to measure both basal and potassium-evoked release of Glu in the anesthetized rat brain. We also addressed the question of signal identity, which is the predominant criticism of these recording technologies. In vivo self-referencing recordings demonstrated that our Glu signals were both enzyme- and voltage-dependent, supporting the identity of L-glutamate. In addition, basal Glu was actively regulated, tetrodotoxin (TTX)-dependent, and measured in the low micromolar range (approximately 2 microm) using multiple self-referencing subtraction approaches for identification of Glu. Moreover, potassium-evoked Glu release exhibited fast kinetics that were concentration-dependent and reproducible. These data support the hypothesis that Glu release is highly regulated, requiring detection technologies that must be very close to the synapse and measure on a second-by-second basis to best characterize the dynamics of the Glu system.

The mechanism of obstetric brachial plexus injury and the role of neurophysiology

The mechanism of obstetric brachial plexus injury and the role of neurophysiology

Feeding differences in pubertal and aged golden hamsters (Mesocricetus auratus) are related to specific cerebral expression pattern of histamine subtype 3 receptor.

The hibernating golden hamster (Mesocricetus auratus) is becoming a useful rodent model to study the neurophysiological role of some neuromediators on vital behaviors such as sleep and thermoregulation. Recent works have shown that the histamine neuroreceptor subtypes (H-sub(1-3)R) are able to modulate such behaviors. Here, specific subtype(s) and cerebral nuclei that were actively operating on feeding behaviors in pubertal and adult hamsters were identified. Of the subtypes assessed, H-sub-3R antagonist (thioperamide) provoked significant (p < .001) changes in behavior (very low total food and water intake) in adults, whereas it did not significantly modify these behaviors in pubertals. The H-sub-3R antagonist's role seemed to be related to elevated amounts of stress-induced damaged neurons displaying, mainly, shrunken crenated cell membranes and altered synaptic processes in limbic areas such as amygdala, cortex, and hippocampus. At the transcription level, an evident expression pattern of H-sub-3R messenger RNA appeared in pubertals, especially in neurons of the cortex and hippocampus, whereas the same trend was featured in amygdalar areas of hibernating adult hamsters, suggesting early H-sub-3R regulatory activities, at least in limbic sites of this rodent model.