| Abstract No.: | B-C2087 |
| Country: | Canada |
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| Title: | DECREASED FREQUENCY OF POSTTRAUMATIC SEIZURES DURING REM SLEEP IS ASSOCIATED WITH AN IMPAIRED POTASSIUM BUFFERING |
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| Authors/Affiliations: | 1 Sinziana Avramescu; 1 Sinziana Avramescu*; 1 Dragos Alexandru Nita; 1 Dragos Alexandru Nita; 1 Igor Timofeev; 1 Igor Timofeev;
1 Laval University - CRULRG, Quebec, QC, Canada
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| Content: | Objectives. Previous studies have shown that the incidence of seizures is clearly attenuated or even disappeared during REM sleep; however, the mechanisms responsible for this phenomenon remain unknown. We undertook this study in order to test whether changes in the concentration of extracellular potassium might be responsible for the decreased frequency of paroxysmal activity during REM sleep compared to slow-wave sleep (SWS) and wake (W).
Materials and Methods. Experiments were performed in non-anesthetized cats with partially isolated suprasylvian gyrus, a well-know model of posttraumatic epilepsy. We used polygraphic recordings (EEG, EOG, EMG) together with potassium-sensitive microelectrodes to measure the concentration of extracellular potassium during different states of vigilance.
Results. All animals with chronic partially deafferented cortex developed paroxysmal EEG activities within the first week and they become generalized in 1 month after cortical deafferentation. The incidence of seizures was maximal during SWS, decreased during W and minimal or absent during REM sleep. Throughout slow-wave sleep potassium concentration decreased during silent states and increased during active states, reaching a variation of 0.2 ± 0.03 mV in control and intact cortex, comparable to the one detected in the undercut 0.21 ± 0.05 mV, but lower than the values reported in ketamine-xylazine anesthetized animals (0.5-1 mM). We additionally found an increased concentration of extracellular potassium in the undercut gyrus with 0.13 ± 0.05 mM during the transitions between SWS and W, which was buffered in 60 ± 12 s, while increasing with 0.51 ± 0.22 mM during the transition between SWS and REM, and was buffered in 120 ± 31 s. In control and intact gyri, the extracellular potassium concentration increase was significantly smaller, enhancing with 0.1 ± 0.02 mM during the transitions between SWS and W, which was buffered in 50 ± 9 s, while increasing with 0.3 ± 0.05 mM during the transition between SWS and REM, and was buffered in 100 ± 17 s.
Conclusion. Our data show an overall impaired buffering of potassium in the undercut cortex, which was more pronounced during REM sleep. This augmentation of extracellular potassium during periods of cortical activation could contribute to the decreased frequency of seizures in these states and could originate in the impaired glial activity described in the injured brain. |
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