THE CHANGES OF EPILEPTOGENIC THRESHOLD IN HIPPOCAMPUS DURING NORMAL SLEEP - WAKING CYCLE.

Our work aimed to investigate the changes of focal epileptogenic threshold at different stages of sleep-waking cycle (SWC). Experiments were carried out in adult Wistar rats. Under ketalar anesthesia electrodes were implanted stereotaxically into the brain structures, according to Paxinos and Watson atlas coordinates. Epiletiform Discharges (ED) were induced by electrical stimulation of dorsal hippocampus. In addition, reduction of neocortical activity via spreading depression (SD) was induced in the neocortex by bilateral application of 12% KCL solution. It was found that EDs were more durable at the stage of slow sleep than in wakefulness. Consequently, during slow sleep, the hippocampal epileptogenic threshold was lowered. Prolongation of EDs of hippocampal origin during SD was also observed in neocortex. According to the data obtained one of important factors increasing susceptibility of hippocampus to EDs, at the stage of slow sleep, should be the weakening of tonic inhibitory influence of the cortex upon hippocampus, resulting in decreased epileptogenic threshold in the latter.

CONNECTION BETWEEN SERUM VASCULAR ENDOTHELIAL GROWTH FACTOR LEVELS AND SEVERITY OF MICROANGIOPATHY IN PATIENTS WITH TYPE 2 DIABETES AND OBSTRUCTIVE SLEEP APNEA.

Our aim was to evaluate the serum vascular endothelial growth factor (VEGF) level in type 2 diabetes patients with comorbid obstructive sleep apnea (OSA) and to compare it in connection with diabetic retinopathy and chronic kidney disease severity. In the prospective cohort study following data were collected: medical anamnesis; demographic and anthropometric data; laboratory (serum VEGF, complete blood count, biochemistry, immunology, complete urine test, including microalbuminuria) and instrumental investigation data (fundoscophy, laboratory polysomnography). From 232 analyzed patients 54 (23.27%) were placed in OSA+ group, 178-OSA- group Mean VEGF value in OSA+ group was significantly higher, than in OSA- group. Serum VEGF level in patients with diabetic retinopathy was signifcantly higher with OSA comorbidity. Pearson correlation coefficient between VEGF and diabetic retinopathy stages, VEGF and CKD stages was significant in both groups. Our study suggests, that the blood VEGF play an important role in microangiopathy severity in patients with T2DM, especially with OSA comorbily.

TONIC INFLUENCE OF NEOCORTEX ON HIPPOCAMPAL SEIZURES.

The interaction between different brain structures could be crucial to predicting seizure occurrence, threshold and spread. Moreover, the sleep-wake cycle and electrical activity of brain structures in different phases of sleep could significantly affect the pattern and extent of seizure spread, and therefore the characteristics of epileptic activity. In this animal model using 15 Wistar rats, we show that the duration of hippocampal seizures, induced by electrical stimulation of the hippocampus, is significantly increased during slow sleep. Moreover, decreasing the electrical activity of the neocortex by cooling of the cortical surface or induction of cortical spreading depression also caused an increase in hippocampal seizure duration. Conversely, warming the cortical surface triggered a remission in spreading depression, in turn restoring the duration of epileptic episodes. Our data suggest that the neocortex probably exerts a tonic inhibitory influence on hippocampal seizures. Thus, cortico-hippocampal interaction could be an important component in the manifestation and generalization of limbic seizures.