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Neuronal Excitation (neuronal + excitation)

Distribution by Scientific Domains

Life Sciences	60%
Medical Sciences	40%

Selected Abstracts

Physiological functions of glucose-inhibited neurones

ACTA PHYSIOLOGICA, Issue 1 2009
D. Burdakov
Abstract Glucose-inhibited neurones are an integral part of neurocircuits regulating cognitive arousal, body weight and vital adaptive behaviours. Their firing is directly suppressed by extracellular glucose through poorly understood signalling cascades culminating in opening of post-synaptic K+ or possibly Cl, channels. In mammalian brains, two groups of glucose-inhibited neurones are best understood at present: neurones of the hypothalamic arcuate nucleus (ARC) that express peptide transmitters NPY and agouti-related peptide (AgRP) and neurones of the lateral hypothalamus (LH) that express peptide transmitters orexins/hypocretins. The activity of ARC NPY/AgRP neurones promotes food intake and suppresses energy expenditure, and their destruction causes a severe reduction in food intake and body weight. The physiological actions of ARC NPY/AgRP cells are mediated by projections to numerous hypothalamic areas, as well as extrahypothalamic sites such as the thalamus and ventral tegmental area. Orexin/hypocretin neurones of the LH are critical for normal wakefulness, energy expenditure and reward-seeking, and their destruction causes narcolepsy. Orexin actions are mediated by highly widespread central projections to virtually all brain areas except the cerebellum, including monosynaptic innervation of the cerebral cortex and autonomic pre-ganglionic neurones. There, orexins act on two specific G-protein-coupled receptors generally linked to neuronal excitation. In addition to sensing physiological changes in sugar levels, the firing of both NPY/AgRP and orexin neurones is inhibited by the ,satiety' hormone leptin and stimulated by the ,hunger' hormone ghrelin. Glucose-inhibited neurones are thus well placed to coordinate diverse brain states and behaviours based on energy levels. [source]

Model of cryptogenic infantile spasms after prenatal corticosteroid priming

EPILEPSIA, Issue 2010
Libor Velí
Summary Infantile spasms (IS) is a devastating epilepsy syndrome of childhood. IS occurs in 3,12-month-old infants and is characterized by spasms, interictal electroencephalography (EEG) hypsarrhythmia, and profound mental retardation. Hormonal therapy [adrenocorticotropic hormone (ACTH), corticosteroids] is frequently used, but its efficacy is tainted by severe side effects. For research of novel therapies, a validated animal model of IS is required. We propose the model of spastic seizures triggered by N -methyl- d -aspartate (NMDA) in infant rats prenatally exposed to betamethasone. The spasms have remarkable similarity to human IS, including motor flexion spasms, ictal EEG electrodecrement, and responsiveness to ACTH. Interestingly, the spasms do not involve the hippocampus. Autoradiographic metabolic mapping as well as tagging of the areas of neuronal excitation with c-fos indicates a strong involvement of hypothalamic structures such as the arcuate nucleus, which has significant bilateral connections with other hypothalamic nuclei as well as with the brainstem. [source]

Long-range oscillatory Ca2+ waves in rat spinal dorsal horn

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2005
Ruth Ruscheweyh
Abstract Synchronous activity of large populations of neurons shapes neuronal networks during development. However, re-emergence of such activity at later stages of development could severely disrupt the orderly processing of sensory information, e.g. in the spinal dorsal horn. We used Ca2+ imaging in spinal cord slices of neonatal and young rats to assess under which conditions synchronous activity occurs in dorsal horn. No spontaneous synchronous Ca2+ transients were detected. However, increasing neuronal excitability by application of 4-aminopyridine after pretreatment of the slice with blockers of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate, ,-aminobutyric acid (GABA)A and glycine receptors evoked repetitive Ca2+ waves in dorsal horn. These waves spread mediolaterally with a speed of 1.0 ± 0.1 mm/s and affected virtually every dorsal horn neuron. The Ca2+ waves were associated with large depolarizing shifts of the membrane potential of participating neurons and were most likely synaptically mediated because they were abolished by blockade of action potentials or N -methyl- d -aspartate (NMDA) receptors. They were most pronounced in the superficial dorsal horn and absent from the ventral horn. A significant proportion of the Ca2+ waves spread to the contralateral dorsal horn. This seemed to be enabled by disinhibition as primary afferent-induced dorsal horn excitation crossed the midline only when GABAA and glycine receptors were blocked. Interestingly, the Ca2+ waves occurred under conditions where AMPA/kainate receptors were blocked. Thus, superficial dorsal horn NMDA receptors are able to sustain synchronous neuronal excitation in the absence of functional AMPA/kainate receptors. [source]

Molecular cloning and expression regulation of PRG-3, a new member of the plasticity-related gene family

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2004
Nicolai E. Savaskan
Abstract Phospholipid-mediated signalling on neurons provokes diverse responses such as neurogenesis, pattern formation and neurite remodelling. We have recently uncovered a novel set of molecules in the mammalian brain, named plasticity-related genes (PRGs), which mediate lipid phosphate phosphatase activity and provide evidence for their involvement in mechanisms of neuronal plasticity. Here, we report on a new member of the vertebrate-specific PRG family, which we have named plasticity-related gene-3 (PRG-3). PRG-3 is heavily expressed in the brain and shows a specific expression pattern during brain development where PRG-3 expression is found predominantly in neuronal cell layers and is already expressed at embryonic day 16. In the mature brain, strongest PRG-3 expression occurs in the hippocampus and cerebellum. Overexcitation of neurons induced by kainic acid leads to a transient down-regulation of PRG-3. Furthermore, PRG-3 is expressed on neurite extensions and promotes neurite growth and a spreading-like cell body in neuronal cells and COS-7 cells. In contrast to previously described members of the PRG family, PRG-3 does not perform its function through enzymatic phospholipid degradation. In summary, our findings feature a new member of the PRG family which shows dynamic expression regulation during brain development and neuronal excitation. [source]

Audiological outcome of the pull-back technique in cochlear implantees,

THE LARYNGOSCOPE, Issue 7 2010
Dietmar Basta PhD
Abstract Objectives/Hypothesis: The distance of the cochlear implant electrode contacts to the modiolus can be reduced by a surgical technique called "pull-back." This procedure changes the location of the fully inserted electrode array by moving the electrode out of the cochlea until the first silicon ring is visible in the cochleostomy. This leads to a more focused stimulation, which in turn could possibly improve hearing performance. The objective of the present study was to investigate the influence of the pull-back technique on frequency difference limens (FDL) and speech perception. Study Design: Double-blind trial. Methods: Twelve pull-back and 12 matched controls (matched by age, gender, duration of deafness, and duration of implant use) were used. Twenty-four patients were implanted with the Nucleus-24 Contour Advance array. In 12 patients the pull-back technique was used and in 12 matched controls a standard insertion technique was applied. Twelve months after the initial stimulation speech perception, spread of neuronal excitation (SOE) at electrodes 5, 10, and 15; and FDLs at 1, 2, and 4 kHz were measured. Results: There was no significant difference of speech perception performance between the two groups. However, the mean FDL for the 4 kHz reference tone was significantly lower in the pull-back group compared to the controls. The SOE was significantly reduced at basal, middle, and apical electrodes in the electrode pull-back group. Conclusions: The pull-back technique seems to have its greatest effect on perimodiolar position in the basal regions of the cochlea. Therefore, it is most likely to observe improved FDL in the 4 kHz region. Current speech recognition tests do not reflect the lower FDL. Laryngoscope, 2010 [source]