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Biomedical subjects

G Juhasz

Publications and source records attributed to G Juhasz.

7 recordsLinked to original sources
PubMed2005

Sumatriptan causes parallel decrease in plasma calcitonin gene-related peptide (CGRP) concentration and migraine headache during nitroglycerin induced migraine attack.

Sumatriptan-induced changes in plasma calcitonin gene-related peptide (CGRP) concentration and headache intensity were investigated in 19 female migraineurs during nitroglycerin-induced migraine attack. Sumatriptan nasal spray was administered 120 min after the onset of the attack. Blood samples were obtained immediately before and 60 min after sumatriptan administration. In those subjects whose migraine attack improved considerably 60 min after the treatment the plasma CGRP concentration decreased significantly (P<0.05). In contrast, plasma CGRP concentration failed to change in patients whose headache did not improve. In addition, plasma CGRP concentrations showed significant positive correlations with the headache scores both 60 and 120 min after sumatriptan administration (P<0.05). According to our results plasma CGRP concentration decreases parallel to headache intensity during sumatriptan treatment and this decrease in CGRP predicts effectiveness of antimigraine drug therapy. This supports that one of the main effects of triptans is to decrease CGRP release.

Biomarkers↗
PubMed1998

Reduction of the extracellular level of glutamate in the median raphe nucleus associated with hippocampal theta activity in the anaesthetized rat.

The relationship between hippocampal activity and the extracellular level of excitatory amino acids in the median raphe nucleus has been studied in urethane anaesthetized rats, using the in vivo microdialysis technique. Dialysates were collected from the median raphe nucleus during two to eight sampling periods of equal length (20 min) and hippocampal electroencephalogram was continuously monitored. For each observation period, the average glutamate level in the median raphe nucleus was determined and the percentage of theta and non-theta segments in the hippocampal recordings was calculated. Theta synchronization, in these experiments, either developed spontaneously or it was elicited by injection of anticholinesterase (Physostigmine or Sintostigmine, i.p.) or by a series of short tail pinches. The relationship between hippocampal activity and glutamate release in the median raphe nucleus was characterized by comparison of the direction of changes in these two parameters in consecutive sampling periods. We found that as long as theta/non-theta ratio changed spontaneously or under the effect of anticholinesterase (n = 7), the extracellular level of glutamate in the median raphe nucleus was elevated during periods dominated by desynchronized hippocampal activity as compared with those mostly containing long and/or frequently occurring theta segments. Such relationship was not observed in the adjacent reticular formation (n = 4) and in the median raphe nucleus during sensory stimulation (n = 2). The present data complete those found earlier indicating that the desynchronizing serotonergic influence originating from the brainstem is maintained by a tonic excitatory input to the median raphe nucleus. Since the majority of glutamatergic afferents to the median raphe nucleus originates from the lateral habenula and the interpeduncular nucleus, known to connect limbic forebrain to the brainstem, theta associated changes in median raphe nucleus glutamate levels might reflect descending forebrain influences, suggesting therefore a feedback regulation of the hippocampal activity involving brainstem structures.

Animals↗
PubMed1997

The contribution of glial cells to spontaneous and evoked potentials.

The mechanism by which brain cells generate alpha and other rhythms remains obscure, and the possible participation of glial cells in the process continues to be debated. We will present data obtained from freely moving rats in which flashes produced by a light emitting diode implanted under the skin of the scalp evoke retinal and cortical responses recorded through electrodes implanted behind the eye and over visual cortex. In the retina, which is a brain-like structure isolated in the periphery during embryology, the b-wave evoked response is thought to be produced by the Müller glial cells as they maintain potassium ion homeostasis in the extracellular space during the synaptic events initiated by rod and cone activation. We will report on the results of a search in this retinal analogue of the brain for spontaneous activity in the EEG spectrum.

Animals↗
PubMed1989

Electrochemical calibration of in vivo brain dialysis samplers.

Measurement of state-related changes in the concentration of an endogenous substance using the in vivo dialysis technique requires a definition of the factors which relate the concentration detected in the outflowing perfusate to the concentration actually occurring in the extracellular space in which the sampler is located. In determine these factors, a rapid and highly accurate detector system is required which measures the concentration recovery in the perfusate and the dead space of the entire sampling system. To reduce the limitations of the microdialysis technique, two electrochemical microcells were developed for calibration of dialysis probes by computerized voltammetry. The electrochemically calibrated samplers were implanted into freely moving cats to measure concentration changes of monoamine metabolites in synchrony with sleep stages identified by polygraphy in order to demonstrate the applicability of electrochemical calibration in dialysis methods used in behavioral investigations.

Animals↗
PubMed1987

Neuronal firing in the pallidal region: firing patterns during sleep-wakefulness cycle in cats.

Neuronal activity was investigated by extracellular microelectrodes in the pallidal region of freely moving cats during wakefulness (W), slow-wave sleep (SWS) and paradoxical sleep (PS). The firing of 150 units from 35 points was examined. On the basis of the modifications of firing rates and patterns during the sleep-wakefulness cycle, 5 groups of neurons were distinguished. Two of these groups were characterized by strong increase of firing rate in W and PS and in one of them this increase preceded the cortical activation at the SWS-PS transition by an average of 26 sec. The role played by the basal forebrain area in the regulation of the sleep-wakefulness cycle is discussed.

Action Potentials↗
PubMedDate not supplied

Analysis of circulation of neuronal activity in the waking cortex.

It is well known that the rhythmic activity of the cerebral cortex is closely associated with a highly organized circulation of neuronal impulses through the networks in which the activity develops. The present study has attempted to determine by quantitative methods, the consistency of this circulation and of its association with the cortical waves, over relatively long periods. Cortical gross waves and neuronal activity have been recorded by means of arrays of extracellular microelectrodes, in freely moving cats as well as in cats immobilized with flaxedil. Autocorrelations have been performed on trains of rhythmic waves and on associated clusters of action potentials; cross-correlations and multiple correlations have been performed between waves and action potentials and between action potentials generated by different groups of neurons. It has been found that the rhythmicity of the waves, the rhythmicity of the associated clusters of action potentials, the time and phase relations between them, and the circulation of neuronal activity through the networks, remain highly consistent over periods as long as two hours.

Action Potentials↗