Effects of total sleep deprivation in rats with hereditary predisposition to audiogenic convulsions

In rats of the Krushinskii-Molodkina (KM) line with hereditary predisposition to audiogenic convulsions there were studied effects of total sleep deprivation for 3, 6, and 9 h by a light arousal or a slow rotation in a roller on spectral EEG characteristics in the wakefulness-sleep cycle, organization of the cycle, and intensity of convulsive symptoms at the recovery period. The data are presented on dynamics of recovery of the cycle structure for 12 h of postdeprivation period. It has been established that during and after the total sleep deprivations of any duration no paroxysmal discharges appear in EEG of hippocampus, caudate nucleus, medial central thalamic nucleus, somatosensory, visual, and auditory cerebral cortex in any of states of the wakefulness-sleep cycle. These deprivations were also shown to have no effect on the latent period value and parameters of generalized tonic-clonal audiogenic convulsions. At the same time, after 6 and 9 h of the total sleep deprivations in a slowly rotating roller there was revealed in some animals a change of the type of response to the sound stimulus. Such decrease of reaction of rats to audiogenic stimuli seems to be due to alertness of the animals. It is stated that in the KM rats, with the hidden convulsive syndrome, we failed to activate epileptiform manifestations by the used types and ways of the total sleep deprivations.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 82–88.Original Russian Text Copyright © 2005 by Vataev, Oganesyan.     

Electroencephalographic analysis of manifestations of latent forms of paroxysmal syndrome in the wakefulness-sleep cycle in rats

An electroencephalographic study of the brain activity in the wakefulness-sleep cycle was carried out on rats of Krushinskii-Molodkina line (KM) with hereditary predisposition to audiogenic convulsions and on Wistar rats that were insensitive to the convulsiogenic sound effect, but with epileptiform manifestations appearing on the background of cadmium intoxication and administration of kainic acid into the caudate nucleus head. There were revealed several EEG patterns whose presence was an indicator of formation of disorders of the CNS activity of the paroxysmal character in the animals. It has been established that in the phase of the rat rapid-wave sleep, a high representation of episodes with predominance of a-diapason EEG oscillations can be considered a specific non-paroxysmal abnormality due to the presence of convulsive syndrome in these animals. It was shown the long steady decrease of sensitivity of KM rats to the convulsiogenic sound effect, which appeared after multiple audiogenic generalized tonicoclonic convulsive attacks, correlated with a decrease of the degree of theta-diapason oscillations and with an increase of representation of alpha-diapason waves on EEG in the state of the animal quiet consciousness. A role of disintegration in activity of the ascending activating brain systems in the animal and human paroxysmal syndromes is discussed.     

Electroencephalographic analysis of manifestations of hidden forms of paroxysmal syndrome in the wakefulness-sleep cycle in rats

An electroencephalographic study of the brain activity in the wakefulness-sleep cycle was carried out on rats of Krushinskii-Molodkina line (KM) with hereditary predisposition to audiogenic convulsions and on Wistar rats that were insensitive to the convulsiogenic sound effect, but with epileptiform manifestations appearing on the background of cadmium intoxication and administration of kainic acid into the caudate nucleus head. There were revealed several EEG patterns whose presence was an indicator of formation of disorders of the CNS activity of the paroxysmal character in the animals. It has been established that in the phase of the rat rapid-wave sleep, a high representation of episodes with predominance of α-diapason EEG oscillations can be considered a specific non-paroxysmal abnormality due to the presence of convulsive syndrome in these animals. There was shown a long steady decrease of sensitivity of KM rats to the convulsiogenic sound effect, which appeared after multiple audiogenic generalized tonicoclonic convulsive attacks, correlated with a decrease of the degree of ?-diapason oscillations and with an increase of representation of α-diapason waves on EEG in the state of the animal quiet wakefulness. The role of disintegration in activity of the ascending activating brain systems in the animal and human paroxysmal syndromes is discussed.     

Long-term action of camphor on "audio-sensitive" rats: Electrophysiological study and mathematical modeling of properties of neuronal networks

Krushinskii-Molodkina (KM) strain rats genetically predisposed to audiogenic convulsive reaction were given repeated camphor injections in gradually increasing doses (starting at the minimum threshold level required for seizures to occur) over a 4–5 month period. Animals were able to tolerate camphor at doses 3/2–3 times convulsion threshold level without seizure occurring once habituation to the action of this convulsant had been developed. At the same time, the cortical motor zone of strain KM rats acquired properties typical of an epileptic focus: spontaneous epileptiform firing peaks were noted in the background electrical activity of this zone. A decline in the parameter reflecting efficacy of the mechanisms underlying recurrent inhibition emerged in the cortical motor zone of strain KM rats receiving camphor from calculating the parameters of neuronal network from spectra of summated potentials (using the model of a neuronal network). It is suggested that the development of compensatory processes making it possible to avoid generalized seizure following administration of camphor in large doses is associated with intensification of inhibitory caudate function and attenuated hippocampal excitation.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 193–200, March–April, 1990.     

Anticonvulsive properties of peptide ACTH4-7 pro-gly-pro detected in amygdaloid kindling and audiogenic epilepsy in rats

Effects of the ACTH4-7 pro-gly-pro, calcium valproate ("Germed", DDR) and nembutal on kindling preparation and audiogenic epilepsy were investigated. Development of after-discharges in response to repeated amygdaloid electrical stimulation was assessed in normal rats and in rats susceptible to audiogenic epilepsy (KM line of rats). ACTH4-7 pro-gly-pro had an anticonvulsant profile. ACTH4-7 pro-gly-pro decreased seizure threshold in the audiogenic epilepsy test, but did not prevent the motor convulsions.     

3H-1-glutamate binding with the synaptic membranes isolated from the cerebral cortex and hippocampus of Krushinski?-Molodkina strain rats

Specific binding of 3H-L-glutamate to synaptic membranes isolated from the cerebral cortex and hippocamp of Wistar and Krushinsky-Molodkina (KM) rats examined both in a quiet awake state and after audiogenic seizures was compared. The dissociation constant (KD) values and binding capacity (Bmax) for KM rats did not differ significantly from the corresponding parameters of binding determined for Wistar rats (KD--89.8 +/- 18.1 and 102.6 +/- 12.5 nm, Bmax--1.23 +/- +/- 0.08 and 1.30 +/- 0.15 pmol/mg for the cortex and hippocamp, respectively). After audiogenic seizures the binding capacity of the hippocamp of KM rats was reduced by 30%. It is suggested that hippocampal glutamate receptors of KM rats are involved in the mechanism of convulsive activity formation.     

Effects of ionotropic glutamate receptor channel blockers on the development of audiogenic seizures in Krushinski-Molodkina rats

The action of noncompetitive blockers of glutamate receptors has been investigated on Krushinski-Molodkina rats genetically-prone to audiogenic seizures. The selective blockers of NMDA receptor channels, memantine and IEM-1921, and their dicationic homologues, IEM-1925 and IEM-1754, capable of blocking in varying degrees both NMDA and Ca-permeable AMPA receptor channels, were studied. The drugs were injected intramuscularly to rats with the different time intervals (30 min, 1, 2 or 3 hours) before sound signal. The effects of the drugs on latent period of initial locomotor activity provoked by audio stimulation (8 kHz sine-wave tone, 90 dB volume), the appearance of clonic convulsions of different intensities, and, finally, tonic convulsions with limb and tail extension were evaluated. Within 30 min after injection IEM-1921 at a dose of 5 mg/kg, 33% of rats manifested a complete absence of convulsive reactions to sound, and in 59% of rats audiogenic seizures occured only in the form of motor excitation without a generalized clonic-tonic convulsions. Memantine at a dose of 5 mg/kg did not cause a complete blockade of seizures, but after 1 h of injection in 50% of the rats and after 2 h in 70% of rats a weakening of the audiogenic seizures to the level of motor excitation only was observed. After 3 hrs after administration of blockers its anticonvulsive action weakened significantly (p < 0.01). Dicationic blockers that block both NMDA and AMPA/kainate receptors, IEM-1925 (in doses of 0.001-20.0 mg/kg) and IEM-1754 (0.025-50.0 mg/kg), did not affect audiogenic clonic-tonic convulsive reactions. The involvement of activation of NMDA and calcium permeable AMPA/kainate receptors in the pathogenesis of audiogenic seizures is discussed.     

Activities of thiamine-dependent enzymes in two experimental models of thiamine-deficiency encephalopathy:

Chronic thiamine deprivation in the rat leads to selective neuropathological damage in brainstem structures whereas treatment with the central thiamine antagonist, pyrithiamine, results in more widespread damage. In order to further elucidate the neurochemical mechanisms responsible for this selective damage, the thiamine-dependent enzyme complex pyruvate dehydrogenase (PDHC) was measured in 10 brain structures in the rat during progression of thiamine deficiency produced by chronic deprivation or by pyrithiamine treatment. Feeding of a thiamine-deficient diet to adult rats resulted in 5–7 weeks in ataxia and loss of righting reflex accompanied by decreased blood transketolase activities. PDHC activities were selectively decreased by 15–30% in midbrain and pons (lateral vestibular nucleus). Thiamine treatment of symptomatic rats led to reversal of neurological signs and to concomitant reductions of the cerebral PDHC abnormalities. Daily pyrithiamine treatment led within 3 weeks to loss of righting reflex and convulsions and to decreased blood transketolase of a comparable magnitude to that observed in chronic thiamine-deprived rats. No significant regional alterations of PDHC, however, were observed in pyrithiamine-treated rats.     

The effect of multiple audiogenic seizures upon the sleep organization in rats

The organization of sleep during and after frequentative convulsions, consisting of 2, 3, or 5 comparatively rare seizures (following one another with a 90-minute interval) or of 3, 5 or 9 comparatively frequent seizures (following one another with a 45-minute interval) of generalized tonic-clonic character in Krushinskii-Molodkina strain rats with inherited predisposition to audiogenic convulsions, was studied. In frequentative convulsions with rare seizures, between separate seizures, passive wakefulness (75.2 +/- 4.6% time) prevailed under low (24.8 +/- 4.3%) slow-wave sleep and full absence of fast-wave sleep. In rats under frequentative convulsions with frequent seizures, in interictal period, only passive wakefulness was observed under reduction of slow-wave sleep and fast-wave sleep, i.e. total sleep deprivation. Minimal latensy of first episodes of the slow-wave sleep after frequentative convulsions was 59.9 +/- 10.8, and of fast-wave sleep: 158.2 +/- 13.4 min. First episodes of slow-wave sleep and fast-wave sleep had normal structure, though they were lesser and shorter than in control experiments. In spite of long-lasting (up to 7 hrs) absence of slow-wave sleep during seizure and prolonged (8.5 hrs) reduction of fast-wave sleep with no subsequent compensatory increase, these conditions occurred in the wakefulness-sleep cycle during 12-hour reconstruction after convulsions. The reconstruction period after frequentative convulsions was characterized by increase in general share of wakefulness and reduction of total slow-wave and fast-wave sleep as compared with control data. Paroxysmal status seems to disorganize work of the brain somnogenic structures. The function of systems responsible for slow-wave sleep are affected to a lesser extent, but disorganization of the system responsible for fast-wave sleep is more significant and associated with mechanisms of starting the phase of sleep in the first place.     

Spectral analysis of EEG in normal rats and in rats genetically predisposed to seizures

Spectral and visual analyses were performed on the EEG of the motor and visual cortex, hippocampus, caudate nucleus, and intralaminary thalamic nuclei in two strains of rats; animals were maintained in a state of "awake immobility." It was found that KM rats, genetically predisposed to audiogenic fits, differed from the Wistar strain not subject to this genetic predisposition in that mean relative intensity of theta rhythm diminished and high amplitude slow irregular hippocampal activity intensified in the neocortex, as did generalized spindling. Susceptibility to seizure was reduced in KM rats as a result of protracted and graded increasing camphor administration to match the level of mean EEG spectral density changes characteristic of the Wistar strain. The part which brainstem reticular formation mechanisms may play in raising susceptibility to seizures is discussed, together with the EEG pattern characteristic of this condition.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 171–179, March–April, 1987.     

Effects of thermal preconditioning on convulsive activity in rats with inheritable form of audiogenic epilepsy

Effects of thermal preconditioning universal recognized method of increase in concentration of inducible Heat shock protein 70 kDa (Hsp70i) on characteristics of convulsive activity in Krushinskii-Molodkina (KM) rats with inheritable audiogenic epilepsy were studied. For the first time, it was found that short-term thermal preconditioning (41 degrees C during 5 minutes) increased duration of the latency of audiogenic seizure onset. Thermal preconditioning resulted in an increase in concentration of Hsp70i in amygdale, hypothalamus, midbrain; the uttermost increase was observed in hippocampus and inferior colliculus: the brain areas responsible for initiation of audiogenic seizures. A coincidence was found in the term of increase in concentration of Hsp70i and the latency of seizure onset (on day 4 after thermal preconditioning). Results of this research confirm the proposition that inducible Hsp70i is capable of taking part in the processes of seizure development in rats with inheritable form of audiogenic epilepsy.     

The phenomenon of lowering a seizure readiness level after frequent audiogenic seizures in Krushinskiĭ-Molodkina rats

The spectral analysis of the EEG activity of several brain structures (somatosensory, visual and auditory areas of the cortex, hippocampus, caudate nucleus and central medial thalamic nucleus) in the wakefulness-sleep cycle in Krushinskii--Molodkina strain rats with inherited predisposition to audiogenic seizures using long-lastint reducing of the seizure readiness level revealed in these animals after frequentative audiogenic generalized tonicclonic seizures, was performed. The reducing susceptibility to convulsiogenic sound stimuli in rats correlated with a decrease of the theta-range' waves level and increase of the expression alpha-range waves in the EEG during wakefulness. Probable role of reorganized functions of ascending activating brain systems in origination of the long reduction of susceptibility to the sound after frequentative audiogenic convulsions in rats is discussed.     

Neurophysiological analysis of the effects of partial paradoxical sleep deprivation

A neurophysiological study was made of the effects of partial and complete paradoxial sleep deprivation by substituting episodes of active wakefulness for spells of paradoxical sleep (PS) of the same duration in the sleep-wake cycle. Neither accumulated need for paradoxical sleep (culminating in increased onset of PS during deprivation), PS rebound during the post-deprivation period, nor dissociation of the stages of paradoxical sleep resulting in their intervening individually at unaccustomed points in the sleep-wake cycle were observed during our experimental procedure. The phenomenon of self-deprivation, increased heart rate, eye movements, and pontogeniculooccipital (PGO) action potentials also failed to occur during the post-deprivation period. It is postulated that PS requirement and the need for periods of wakefulness stem from the same neurochemical alterations.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 20–28, January–February, 1988.     

Effects of Neonatal Treatments on Pain and Audiogenic Sensitivity and Brain Content of Monoamines in Adult Rats

In adult Wistar, KM, and Wag/Rij rats, the threshold of pain sensitivity (tail-flick test) and audiogenic sensitivity were estimated after neonatal administration of Semax (analog of ACTG_4–10 fragment) or after placebo (administration of saline for the control of the effect of neonatal pain stimulation). These neonatal treatments did no affect the rates of sensomotor development at an early age (Fox tests), i.e., did not affect directly the physiological activity of rat pups at the age of up to 21 days. In all control rats injected with saline (pain stimulation), the latencies of audiogenic fits increased reliably, while their degree decreased. Administration of Semax raised these parameters to the level of those in intact animals, i.e., increased the sensitivity to sound. Neonatal administration (per os) of caffeine to KM rats increased reliably the latency of audiogenic fits. The thresholds of pain sensitivity in the rats of all strains were significantly lower saline injected animals than in the intact control, just as the level of dopamine in the hippocampus of KM rats. These data are interpreted as an evidence of changes in the development of some brain systems in response to neonatal treatments.     

Audiogenic kindling changes the subunit composition of BK-channels in dentate gyrus of Krushinskii-Molodkina rats

Subunit composition of voltage- and Ca²⁺-sensitive high-conductance K⁺ channels (BK channels) in dentate gyrus (DG) of Krushinskii-Molodkina (KM) rats, genetically prone to audiogenic seizures, was compared with that of normal Wistar rats, resistant to sound effects. Additionally, long-lasting changes in protein expression of α- and β4-subunits in DG of KM rats after audiogenic kindling (model of temporal lobe epilepsy) was investigated. Western blot analysis revealed no differences between the levels of the pore-forming α-subunit expression in DG of KM and Wistar rats. In contrast, the level of brain-specific auxiliary β4-subunit in DG of KM rats was increased twofold in comparison to that in Wistar rats. It is likely that the observed changes in the BK channel α/β4 subunits ratio can prevent the development of excessive neuronal exitability in DG of KM rats. The results obtained on the model of audiogenic kindling (20 convulsion fits) confirmed this assumption. Thus, α-subunit expression levels in DG of KM rats on day 3 and 14 after the last seizure were increased 2.5 times in comparison with intact KM rats. The expression level of β4 in DG of KM rats 3 days after kindling was reduced to 30% of the control level. On day 14 after finishing audiogenic kindling, a further reduction of β4 protein expression level occurred. We suggest that the changes in the subunit composition of BK channels in DG following chronic seizures can alter functional properties of DG as a physiological filter, which normally prevents the propagation of epileptiform activity in the hippocampus.     

Audiogenic kindling in WAG/Rij rats: change in behavioral and electrophysiological responses to repetitive short acoustic stimulation

Running and tonic convulsions induced by sound stimulation (audiogenic seizures, AS) are known to be brainstem-dependent, but their repeated induction leads to the recruiting forebrain structures into AS expression manifested by the development of clonic convulsions and cortical epileptic activity (audiogenic kindling). Behavioral and electrophysiological manifestations of audiogenic kindling were studied in AS-prone WAG/Rij rats exhibiting two types of genetically determined generalized seizures: convulsive audiogenic and nonconvulsive absence (spontaneous spike-wave discharges generated by thalamocortical circuits). Twenty three repeated (with 2 days intervals) sound stimulations inducing a short running episode led to a progressive increase in AS duration from 6.2 +/- 0.4 s to 24.7 +/- 2.9 s mainly due to the appearance of additional postrunning facial-forelimb clonic convulsions of increasing duration and severity. Fully kindled (Racine's stage 5) seizures were accompanied by a bilateral slow-potential wave of cortical spreading depression (SD) nonsynaptically propagating to both striata and by a long-term postictal suppression of spontaneous absence seizures. Neither corticostriatal SD, nor the spike-wave discharges suppression were observed after running induced by sound in non-kindled rats or by attenuated (subthreshold for clonus) sound in kindled rats. Subthreshold stimulation of kindled rats provoked postictal high-amplitude spiking in the cortex. It is concluded that the recruitment of the cortex into a kindled AS network triggers a corticostriatal SD which may underlie the postictal inhibition of non-convulsive seizures, which follow the kindled AS.     

Spectral and coherence EEG analysis of rats differing in the level of seizure readiness

The resting EEGs of several brain structures (motor and visual cortex, caudate nucleus and intralaminar thalamic nuclei) were submitted to spectral and coherence computer analyses in two rat strains. Genetically predisposed to convulsive state KM rats were shown to differ from nonpredisposed Wistar rats in EEG spectral properties. KM rats EEG pattern was characterized by increase of low frequencies (1-2 Hz) power and decrease of faster activity (5-12 Hz) power in cortical spectrograms as well as by decrease of caudate nucleus EEG absolute power. The coherence value between cortical or subcortical structures at below 4 Hz was intensified in KM rats. Reinforcement of cortical auto-oscillating properties manifested by ECoG synchronization in cortical-thalamic resonance interaction as well as weakening of striatal inhibitory system may constitute neurophysiological mechanisms of enhanced convulsive readiness. The probable role of mediator imbalance in these mechanisms is discussed.     

A morphofunctional analysis of the participation of the cerebral cortex in the habituation of Krushinski?-Molodkina strain rats to an epileptogenic stimulus

Systematic action of epileptogenic stimulus (sound) leads to gradual lowering of the level of convulsive readiness (LCR) in rats of KM (Krushinski'i-Molodkina) line to the formation of the habituation, to blocking of convulsive seizures. It is shown that at single action of sound, functional switching-off of the cerebral cortex causes LCR lowering but does not prevent the development of the epileptiform seizure. Alongside with it, in conditions of repeated sound action, functional decortication considerably retards LCR lowering. After cessation of the cortical depression, during which the rats were given systematic sound exposition, sharp LCR lowering takes place. If the habituation has been already formed, then the subsequent switching-off of the cortex does not lead to LCR growth. Ultrastructural characteristics of asymmetric axo-dendritic and axo-spine synapses in the auditory cerebral cortex of KM line rats in the moment of convulsive seizure testifies to their active functioning, while against the background of short-term habituation to epileptogenic stimulus signs of lowering of the efficiency of synaptic transmission are revealed in these synapses. The obtained results allow to suggest that in the rats of KM line the neocortex takes part in antiepileptic defensive reactions, in LCR regulation in connection with formation of the habituation to systematic action of epileptogenic stimulus.     

Effects of sleep deprivation on respiratory events during sleep in healthy infants

This study was designed to determine the effects of sleep deprivation on respiratory events during sleep in healthy infants. Ten unsedated full-term infants (1-6 mo) were monitored polygraphically during "afternoon naps" on a control day and on the day after sleep deprivation. Respiratory events, i.e., central apnea, obstructive apnea and hypopnea, and periodic breathing were tabulated. Results for respiratory events were expressed as 1) indexes of the total number of respiratory events and of specific respiratory events per hour of total sleep (TST), "quiet" sleep (QS) and "active" sleep (AS) times; 2) total duration of total and specific respiratory events, expressed as a percentage of TST, QS, and AS times. After sleep deprivation, significant increases were observed for 1) respiratory event (P less than 0.001), central apnea (P less than 0.05), and obstructive respiratory event (P less than 0.01) indexes; 2) respiratory event time as a percentage of TST (P less than 0.002) and as a percentage of AS time (P less than 0.001); 3) obstructive respiratory event time as a percentage of TST (P less than 0.01), QS (P less than 0.05), and AS times (P less than 0.002). The present study shows that short-term sleep deprivation in healthy infants increases the number and timing of respiratory events, especially obstructive events in AS.     

Training of rats of the Wistar and Krushinskii-Molodkinaia lines in a radial maze

The experiments were conducted on rats of Wistar (W) and Krushinsky--Molodkina (KM) (with audiogenic epilepsy) lines in 12-rays radial-symmetrical labyrinth. The trained rats of W line made less erroneous (repeated) visits to the labyrinth corridors than the rats of KM line. The corridors repeatedly visited by the rats of W line were more frequently situated near the unvisited corridors. No definite sequence of corridors' visiting by the rats of both lines was observed; still there was a tendency to choose corridors the most remoted from each other. This tendency intensified in the process of training. This is considered as one of tactics of rats' behaviour, providing for adequate reactions in definite surrounding conditions.