B. Janković

Effect of neurotoxin DSP4 on EEG power spectra in the rat acute model of epilepsy

The effect of the adrenergic neurotoxin N-(chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4) on electroencephalographic (EEG) activity was studied in the model of epilepsy induced by systemic application of penicillin (1,000,000 IU/kg, i.p). DSP4 (50 mg/kg, i.p.) was administrated to male Wistar rats, while the control animals were rats from the same litters. EEG activity was recorded in acute and chronic experiments 3 or 4 weeks after DSP4 treatment, before and after penicillin administration. Occasional locus coeruleus (LC) stimulation served as an electrophysiological test of DSP4 toxic effect. EEG power spectra in DSP4 treated animals showed a tendency to be greater in lower frequency bands than in controls before penicillin administration; there was almost no effect of electrical LC stimulation, regardless on penicillin treatment. In the model of epilepsy, the mean total EEG power spectra were greater in the period of 135-330 min after penicillin administration, as well as during 345-540 min, in DSP4 treated animals as compared to the controls. It seems that neurotoxin DSP4 is an optimal tool for studying the removal of LC influence in the acute model of epilepsy. It is also suggested that norepinephrine (NE) may have a modulatory role in the systemic penicillin epilepsy.

Changes in electrical activity of the cockroachBlatta orientalis L. brain induced by anti-lobster brain antibody

Bei mit Langustenhirn immunisierten Kaninchen werden Anti-Hirn-Antikörper gebildet. Werden diese auf die Hirnoberfläche der SchabeBlatta orientalis L. gebracht, so kommt es zu erheblichen Veränderungen in der elektrischen Hirntätigkeit des Insekts.

SLOW OSCILLATIONS OF THE PURKINJE CELL FIRING RATE INDUCED BY ELECTRICAL STIMULATION OF THE LOCUS COERULEUS IN RATS

In anesthetized Wistar rats, we studied the effect of electrical stimulation of the locus coeruleus (LC) on the firing rates of Purkinje cells using spectral analysis. The frequency of extracellularly recorded activity of Purkinje cells was measured before and during the 1st, 5th, 6th, and 11th min after cessation of 10-sec-long LC stimulations. Spectral analysis of the Purkinje cell firing rates (imp./bin, the bin duration was 2-8 sec) for 60- to 120-sec-long intervals was performed using fast Fourier transformation after digital conversion of unitary spikes. Mean power spectra of the Purkinje cell firing rates (derived from 8-sec-long consecutive epochs at a sampling rate of 256 sec-1) showed an increase in the slow frequency range (0.1-1.0 Hz) after LC stimulation, particularly due to the slowest components (below 0.5 Hz). This effect lasted more than 1 min and usually less than 6 min after cessation of LC stimulation and could be interpreted as the development of slow oscillations in the Purkinje cell firing. Our results suggest that slow oscillations of the firing rate of cerebellar output neurons, induced by LC stimulation, reflect a specific coordination of the cerebellar neuronal activities (important for a central norepinephrine influence) in regulation of different pathological states.

Changes in neuropeptide levels after brain damage in rats

The physiological and pathophysiological roles of neuropeptides are still not clear. The aim of our study was to detect long lasting changes of vasoactive-intestinal peptide (VIP), somatostatin (SOM) and substance P (SP) contents in the rat cerebral cortex and hippocampus after brain lesion. The experiments were performed on groups of adult male Wistar rats. The first group consisted of animals with unilateral ablation of the sensorimotor cortex performed at the age of 60 days. The second group was a control one (rats of the same age but with an intact brain). Both groups of animals were sacrificed at the age of 90-105 days and radioimmunoassay was used to determine amounts of VIP, SOM and SP. The mean values of VIP levels were decreased significantly only in contralateral cortical areas, while there was an increase of SP in lesioned animals. Our results suggest that descrete changes in neuropeptide levels occur during restorative processes after brain lesion.

EFFECT OF EARLY CORTICAL LESION ON THE ACUTE MODEL OF EPILEPSY

The experiments were performed in order to investigate the sparing of function following early postnatal cortical lesion in the acute rat model of epilepsy. Sensomotor cortex was unilaterally removed at 9 and 10 days of postnatal age in lesioned animals, while control animals were only sham operated (at the same early stage of life) or non‐operated (before implantation of the electrodes). Seizure activity was recorded by means of electroencephalograms at adult stage of life induced by parenteral administration of penicillin (1 000 000 I.U./kg, i.p.). Our results showed that when the cortical lesion was performed in infancy (on the contrary to the lesion performed in adulthood) there was no prolongation of seizure activity in an acute model of epilepsy.