Comparison of spontaneous and evoked epileptiform activity in three in vitro epilepsy models

Rat neocortical slices express spontaneous epileptiform activity after incubation with GABA(A) receptor blocker bicuculline (BIC, 20 microM), with potassium channel blocker 4-aminopyridine (4-AP, 50 microM) or in Mg(2+)-free medium (LMG). Various parameters of spontaneous and evoked epileptiform discharges and their pharmacological sensitivity were analysed using extracellular field potential recordings in this comparative in vitro study. All types of convulsant solution induced spontaneous epileptiform activity, however, the analysed parameters showed that characteristics of epileptiform discharges are rather different in the three models. The longest duration of discharges was recorded in LMG, while the highest frequency of spontaneous events was detected in 4-AP. The epileptiform field responses elicited by electrical stimulation appeared in an all-or-none manner in BIC. On the contrary, in 4-AP and in LMG the amplitude of the responses increased gradually with increasing stimulation intensities. The NMDA receptor antagonist D,L-2-amino-5-phosphonovaleric acid (APV, 25 microM) abolished the LMG induced spontaneous epileptiform activity and significantly reduced the frequency of the epileptiform discharges in BIC and 4-AP. Blocking the AMPA type of glutamate transmission with 1-(aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466, 40 microM) rapidly abolished BIC-induced spontaneous epileptiform activity and caused a significant decrease in the frequency of 4-AP induced spontaneous epileptiform discharges. However, it had only a weak effect on the LMG-induced epileptiform activity. We conclude that the contribution of NMDA and AMPA types of glutamate receptors to the development and maintenance of epileptiform activity in cortical cell assemblies is different in the three models. There are significant alterations in contribution of NMDA and AMPA types of glutamate receptors to the above-mentioned processes in the different convulsants. In BIC the synchronisation is mainly due to the altered network properties, namely inhibition is reduced in the local circuits. Although inhibition is reduced in the local circuits, the AMPA receptor antagonist relatively easily blocked the synchronised excitation. In 4-AP, and especially in LMG, changes in the membrane characteristics of neurones play a crucial role in the increased excitability. In this case the AMPA antagonist was less effective.

Altered electrophysiological characteristics of developing rat cortical neurones after chronic methylmercury chloride treatment

The effect of methylmercury chloride on the excitability of developing cortical neurons was tested. Methylmercury was administered in the drinking water to pregnant rats during gestation and suckling period and the offspring were investigated. The electrical characteristics of the neuronal membranes as well as the synaptic responses evoked by electrical stimulation of the corpus callosum were measured in brain slices. Slices prepared from the somatosensory cortex of 4-week-old rats were analyzed using sharp electrode intracellular microelectrophysiological recording technique. Long-lasting treatment with low doses of methylmercury chloride caused a slight decrease in the membrane potential and in the amplitude of spikes together with an enhanced excitability. Some of the treated animals were grown up without any further methylmercury application, and their offspring (second generation) were also studied electrophysiologically. These untreated offspring had normal neuronal characteristics. The altered membrane characteristics detected in the 4-week-old MeHg treated animals might be the consequence of the abnormal developmental processes taking place in the presence of MeHg which may alter the normal neuronal excitability. Besides this, the acute toxic effect of Hg(2+), which was present in the brain at the time of investigations, has to be taken into consideration.

An in vitro electrophysiological and Co2+-uptake study on the effect of infraorbital nerve transection on the cortical and thalamic neuronal activity

Changes of neuronal membrane characteristics in somatosensory barrel cortex and barreloid thalamus were investigated in rats following unilateral transection of the infraorbital nerve. Kainate induced Co2+-uptake method and image analysis were used to assess the Ca2+ permeability of non-NMDA (N-methyl-D-aspartate) glutamate receptors. Changes in some biophysical parameters of the affected cortical neurons were also investigated by intracellular recording in slice experiments. The altered neuronal activity was measured on days 1, 5 and 14 after surgery. Kainate induced Co2+ uptake increased markedly reflecting enhanced Ca2+ permeability of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate/kainate (AMPA/KAIN)-type receptors. Changes were more pronounced in the cortex than in the thalamus and peaked on the first day following nerve transection. After that, parameters gradually returned to the normal level. However, a small enhancement was still detectable in the cortex at the end of the 2-week-long observation period. In parallel with the increased Co2+-uptake, moderate membrane potential changes, stronger spiking activity and enhanced excitability were characteristic for cortical neurons. The observed alterations in neuronal characteristics underlie the reorganization and regeneration processes following injuries or surgeries. We can conclude that immediate change of the receptive field in the barrel cortex following unilateral nerve transection is based on changes in biophysical parameters of the neurons. Altered peripheral activation evokes changes in the neuronal activity, thus providing opportunity for a quick synaptic rearrangement. AMPA/KAIN-type glutamate receptors have a decisive role in the regulation of these processes. This kind of synaptic plasticity is more significant in the cortex than in the thalamus.

Effect of a glutamate receptor antagonist (GYKI 52466) on 4-aminopyridine-induced seizure activity developed in rat cortical slices

In the present experiments we have tested the effect of the noncompetitive AMPA antagonist GYKI 52466 (20-80 microM) on spontaneous epileptic discharges developed as the consequence of 4-aminopyridine application in neocortex slices of adult rats. Parallel to the changes of spontaneous activity, the field potentials, evoked by electrical stimulation of the corpus callosum, were also analyzed. Glass microcapillary extracellular recording electrode was positioned in the third layer of the somatosensory cortex slice, while the stimulating electrode was placed at the border of the white and gray matter. 4-aminopyridine and GYKI 52466 were bath-applied. The application of 40 microM GYKI 52466 caused about 40% decrease in the frequency and the amplitude of spontaneous seizures as well as the duration of each discharges developed in 4-amino-pyridine. Pre-incubation with the AMPA antagonist effectively inhibited both the development of seizure activity and the maintenance of the discharges. GYKI 52466 also decreased the duration and amplitude of field responses evoked by stimulation of the corpus callosum. This inhibitory effect was dose-dependent. Our data in the in vitro cortex slice epilepsy model suggest that the non-competitive AMPA antagonist GYKI 52466 is a potent anticonvulsant and neuroprotective compound because it reduced the fully developed epileptic discharges or prevented their development.

Unstable pelvic fractures in children

A total of 3561 freshly injured children received treatment at the paediatric trauma department of the National Institute of Traumatology between 1984 and 1994. Out of these 38 (approx. 1%) had pelvic fractures. Based on the classification of Tile and Laer, 15 pelvic fractures were diagnosed to be unstable, from which 8 were polytraumatised, 4 shocked and 1 was a casualty. Run downs could be considered as the main cause of these fractures. Conservative treatment was provided for 13 unstable cases (bed rest: 5, band suspension: 1, femur skeletal traction: 4, femur traction and band suspension: 3). Surgery was performed in 2 cases (symphysis cerclage: 1, acetabulum plate o.s.: 1). Eleven patients were called in for late controls (after 3 years). Subsequent complications were: pain: 3, limb shortening: 4, lumbal scoliosis: 1, minor pelvic deformations: 4, partial necrosis of caput femoris: 2. The subjective complaints of 3 adolescent cases seem to be small in number, however, it is a fair assumption that the control period of 3-6 years later is not enough to form a comprehensive conception on the nature of early degenerative deformations occurring later, e.g. during adulthood. Because of further surgeries and examinations, correct traction and suspensional treatment can only be carried out with great difficulties regarding children. Therefore, posterior stabilisation of the pelvic ring must be planned with percutaneous sacroiliac pinning or screwing in unstable cases.

[Classification of distal radius fractures and its diagnostic value]

In the conservative treatment of distal radial fractures the main problem is redislocation due to instability. We evaluated the three classification methods most often used to find out how well the different groups correspond to instability and severity of fractures-thus what their prognostic value is in the probable recovery time. Based on an analysis of 633 cases, we found that neither the most often used Frykman nor the AO and older classifications have any practical significance in this respect.

Occult distal radial fractures

The radiological diagnosis of distal radial fractures is usually easy, but some fractures without displacement cannot be detected at the first examination. In this retrospective study of 626 wrist injuries diagnosed as "wrist sprain" we found 39 distal radial fractures which were discovered only after repeated examinations. The incidence of distal radial fractures was much higher than other wrist fractures that were diagnosed after repeated examinations. Repeat standard four-view X-ray examination, as well as other imaging methods, are necessary to diagnose these fractures.

Epidemiology of distal radius fractures in Budapest. A retrospective study of 2,241 cases in 1989

Retrospective data concerning 2,223 patients with fracture of the distal radius were related to the age- and sex-profiles of the population. Compared with observations from other countries, we found a similar sex ratio with a steep rise in fracture incidence in women after age 30-40. Our data did not permit calculation of absolute fracture incidence rates.

[Connection between instability and redislocation of conservatively treated fractures of the distal end of the radius]

Authors analyse from the viewpoint of instability the radiological data of the fractures of the distal end of the radius. They state that the redislocation in conservative treatment is a process going together with the healing of the fracture, the measure of which is determined first of all by the instability. To achieve better results, in unstable fractures, attention is called to the necessity of operative treatment.