The multiple effects of ketamine on the electroencephalographic activity in wag/rij rats

Item does not contain fulltextThe effects of ketamine, a non-competitive antagonist at the NMDA receptor, were studied on the EEG in a genetic animal model of generalized absence epilepsy - the WAG/Rij rat strain. Animals of this strain display spontaneous occurring generalized spike-wave discharges (SWDs) in EEG. Ketamine was administered i.p., in a dose of 3, 6, 15 and 30 mg/kg. Biphasic effects of ketamine were observed. The first phase was a dose-dependent suppression of SWDs, followed by a second phase characterized by the facilitation of SWDs. This increase of the discharges was expressed first as an increased number of SWDs, and later on as a significant prolongation of individual discharges. An obvious amplitude modulation of the discharges in this period was also found. During the period of suppression of spike-wave activity, a new phenomenon was observed: quasi-periodic groups of spikes or wave-spikes, with an internal frequency of 4 - 5 Hz and a periodicity of about 5 seconds. That quasi-periodic activity vanished few minutes prior to the recovery of the classical SWDs. However, a specific 5 second amplitude modulation of SWDs remained also in the recovery period. The propensity of that specific ketamine-induced activity was found to be correlated with propensity of SWDs in background EEGs of drug-free animals. It can be concluded that ketamine has more effects on the EEG than previously assumed which cannot be explained by a simple blockade of the NMDA receptor. It is also thought that the obtained specific dynamics of SWDs' frequency may be caused by changes in the activity of the thalamo-cortical pacemaker that is generating SWD

Time-frequency dynamics of spike-wave discharges in absence epilepsy patients using wavelet transform

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The multiple effects of ketamine on the electroencephalographic activity and behavior in wag/rij rats

Contains fulltext : 64515.pdf (publisher's version ) (Closed access)The effects of ketamine, a non-competitive antagonist at the NMDA receptor, were studied on the EEG in a genetic animal model of generalized absence epilepsy - the WAG/Rij rat strain. Animals of this strain display spontaneous occurring generalized spike-wave discharges (SWDs) in EEG. Ketamine was administered i.p., in a dose of 3, 6, 15 and 30 mg/kg. Biphasic effects of ketamine were observed. The first phase was a dose-dependent suppression of SWDs, followed by a second phase characterized by the facilitation of SWDs. This increase of the discharges was expressed first as an increased number of SWDs, and later on as a significant prolongation of individual discharges. An obvious amplitude modulation of the discharges in this period was also found. During the period of suppression of spike-wave activity, a new phenomenon was observed: quasi-periodic groups of spikes or wave-spikes, with an internal frequency of 4 - 5 Hz and a periodicity of about 5 seconds. That quasi-periodic activity vanished few minutes prior to the recovery of the classical SWDs. However, a specific 5 second amplitude modulation of SWDs remained also in the recovery period. The propensity of that specific ketamine-induced activity was found to be correlated with propensity of SWDs in background EEGs of drug-free animals. It can be concluded that ketamine has more effects on the EEG than previously assumed which cannot be explained by a simple blockade of the NMDA receptor. It is also thought that the obtained specific dynamics of SWDs' frequency may be caused by changes in the activity of the thalamo-cortical pacemaker that is generating SWD

Some peculiarities of time-frequency dynamics of spike-wave discharges in humans and rats

Contains fulltext : 56663.pdf (publisher's version ) (Closed access)Objective - Time–frequency dynamics of spike–wave discharges (SWDs) were investigated in patients with absence seizures and in WAG/Rij rats, a genetic model of absence epilepsy using a specially developed wavelet transform. Methods - Two types of SWDs were analyzed in both species: the most frequently occurring discharges (of minimal 3.6–4.0 s or more) and shorter ones recorded from various cortical regions. Results - The more prolonged discharges had two phases: during the initial part (from tenth of seconds to 1 s) of the seizure the frequency decreased quickly from 5 to 3.5 Hz in patients and from about 15 to 10 Hz in rats. A slower frequency decrease with periodical fluctuations was observed in both species during the second part of the discharge: the frequency decreased towards the end of the discharge to 3 Hz in patients and to 6–7 Hz in rats. The frequency of the short discharges decreased fast during the whole discharge: from 5 to 2–2.5 Hz and from about 15 to 5 Hz in patients and rats, respectively. Conclusions - Comparison of data obtained in patients with typical absence epilepsy and WAG/Rij rats with genetic absence epilepsy revealed that the time–frequency dynamics of SWDs had similar properties but in a different frequency range. Significance - The study of time–frequency dynamics using this specially developed wavelet transform revealed two different types of SWDs, which most likely represent different dynamics in the cortico-thalamo-cortical loop during shorter and more prolonged discharges.8 p

The multiple effects of ketamine on the electroencephalographic activity in wag/rij rats

The effects of ketamine, a non-competitive antagonist at the NMDA receptor, were studied on the EEG in a genetic animal model of generalized absence epilepsy - the WAG/Rij rat strain. Animals of this strain display spontaneous occurring generalized spike-wave discharges (SWDs) in EEG. Ketamine was administered i.p., in a dose of 3, 6, 15 and 30 mg/kg. Biphasic effects of ketamine were observed. The first phase was a dose-dependent suppression of SWDs, followed by a second phase characterized by the facilitation of SWDs. This increase of the discharges was expressed first as an increased number of SWDs, and later on as a significant prolongation of individual discharges. An obvious amplitude modulation of the discharges in this period was also found. During the period of suppression of spike-wave activity, a new phenomenon was observed: quasi-periodic groups of spikes or wave-spikes, with an internal frequency of 4 - 5 Hz and a periodicity of about 5 seconds. That quasi-periodic activity vanished few minutes prior to the recovery of the classical SWDs. However, a specific 5 second amplitude modulation of SWDs remained also in the recovery period. The propensity of that specific ketamine-induced activity was found to be correlated with propensity of SWDs in background EEGs of drug-free animals. It can be concluded that ketamine has more effects on the EEG than previously assumed which cannot be explained by a simple blockade of the NMDA receptor. It is also thought that the obtained specific dynamics of SWDs' frequency may be caused by changes in the activity of the thalamo-cortical pacemaker that is generating SWD

Time-frequency analysis of spike-wave discharges using a modified wavelet transform

The continuous Morlet wavelet transform was used for the analysis of the time-frequency pattern of spike-wave discharges (SWD) as can be recorded in a genetic animal model of absence epilepsy (rats of the WAG/Rij strain). We developed a new wavelet transform that allows to obtain the time-frequency dynamics of the dominating rhythm during the discharges. SWD were analyzed pre- and post-administration of certain drugs. SWD recorded predrug demonstrate quite uniform time-frequency dynamics of the dominant rhythm. The beginning of the discharge has a short period with the highest frequency value (up to 15 Hz). Then the frequency decreases to 7-9 Hz and frequency modulation occurs during the discharge in this range with a period of 0.5-0.7 s. Specific changes of SWD time-frequency dynamics were found after the administration of psychoactive drugs, addressing different brain mediator and modulator systems. Short multiple SWDs appeared under low (0.5 mg/kg) doses of haloperidol, they are characterized by a fast frequency decrease to 5-6 Hz at the end of every discharge. The frequency of the dominant frequency of SWD was not stable in long lasting SWD after 1.0 mg/kg or more haloperidol: then two periodicities were found. Long lasting SWD seen after the administration of vigabatrin showed a stable frequency of the discharge. The EEG after Ketamin showed a distinct 5 s quasiperiodicity. No clear changes of time-frequency dynamics of SWD were found after perilamine. It can be concluded that the use of the modified Morlet wavelet transform allows to describe significant parameters of the dynamics in the time-frequency domain of the dominant rhythm of SWD that were not previously detected