Recently it was established that early long lasting treatment with the anti-absence drug ethosuximide (ETX) delays the occurrence of absences and reduces depressive-like symptoms in a genetic model for absence epilepsy, rats of the WAG/Rij strain. Here it is investigated whether anti-epileptogenesis (chronic treatments with ETX for 2 and 4 months) affects REM sleep in this model. Four groups of weaned male WAG/Rij rats were treated with ETX for 4 months, two groups for 2 months (at 2-3 and 4-5 months of age), the fourth group was untreated. Next, the rats were recorded 6 days after the last day of the treatment for 22.5 h. Non-REM sleep and REM sleep parameters and delta power were analyzed in four characteristic and representative hours of the recoding period. Four months treatment with ETX reduced the amount of REM sleep and REM sleep as percentage of total sleep time. Other sleep parameters were not affected by the treatment. Clear differences between the various hours of the light-dark phase in amounts of non-REM and REM sleep and delta power were found, in line with commonly reported circadian sleep patterns. It can be concluded that the reduction of REM sleep is unique for the early and long lasting chronic treatment. The outcomes may explain our earlier finding that a reduction of REM sleep might alleviate depressive like symptoms.
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