Seizures In Immature Rats Research Articles

Padsevonil suppresses seizures without inducing cell death in neonatal rats.

Padsevonil (PSL) is a rationally designed anti-seizure medication (ASM) which has overlapping mechanisms of action with the two most common ASMs used for neonatal seizures, phenobarbital (PB) and levetiracetam (LEV). Here we evaluated the anti-seizure properties of PSL across the neonatal and adolescent period in rats in the pentlyenetetrazole (PTZ) induced seizures model. Postnatal day (P)7, P14 and P21 Sprague-Dawley rat pups were pre-treated with PSL (1-30mg/kg), and assessed for seizure latency and severity 30min later following injection of PTZ. A separate cohort of P7 pups were treated with neonatal ASMs and euthanized 24h later (on P8) to assess induction of cell death, a feature common to many ASMs when given to P7 rodents. This effect has been extensively reported with PB, but not with LEV. Cell death was assessed by PathoGreen staining. PSL suppressed PTZ-evoked seizures across multiple age groups, particularly at higher doses, without producing increased cell death compared to vehicle. The effects of PSL were particularly notable at suppressing tonic-clonic seizure manifestations (82% of P7 and 100% of P14 and P21 animals were protected from tonic-clonic seizures with the 30mg/kg dose). PSL displayed dose-dependent anti-seizure effects in immature rodents in the PTZ model of seizures in immature rats. While many ASMs, including PB, induce cell death in neonatal rats, PSL does not. This suggests that PSL may offer therapeutic benefit and a favorable safety profile for the treatment of neonatal seizures.

Perampanel exhibits anticonvulsant action against pentylentetrazol-induced seizures in immature rats

Perampanel is a new antiepileptic drug with unique mechanism of action – antagonism of AMPA receptors. Its action in immature animals is not yet sufficiently known therefore we started to study anticonvulsant action of perampanel pretreatment (1–20 mg/kg i.p.) against seizures elicited by pentylenetetrazol. Three age groups of rats were examined – 12, 18 and 25 days old. Perampanel selectively suppressed the tonic phase of generalized seizures in the two younger groups and whole tonic-clonic seizures in the 25-day-old group. It exhibited also an anticonvulsant action against minimal clonic seizures present in control 18- and 25-day-old rats.Perampanel is an effective anticonvulsant drug even at very early stages of brain development.

Prenatal stress increased γ2 GABAA receptor subunit gene expression in hippocampus and potentiated pentylenetetrazol-induced seizure in rats.

Objective(s):Stress during pregnancy is able to bring extensive effects on neurobehavioral development in offspring. The GABAergic system plays a pivotal role in neuronal excitability, which can be affected by prenatal stress (PS). This study aimed to evaluate impact of the PS on γ2 subunit of gamma-aminobutyric acid A (GABAA) receptor gene expression in the hippocampus and seizure induced by pentylenetetrazol (PTZ) in developing rats.Materials and Methods:In this experimental study, female Wistar rats were exposed to restraint stress during gestation and their offspring were studied on postnatal days 14 and 21 (P14 and P21, respectively) for epileptic behaviors and γ2 GABAA receptor subunit gene expression. Quantitative real-time PCR was used for evaluating the γ2 GABAA receptor subunit gene expression in rat pups. Meanwhile, PTZ was injected into the pups, and seizure behaviors were recorded for 60 min. Results:The results showed that γ2 subunit mRNA expression significantly increased in the hippocampus of the stressed pups. The expression level of γ2 subunit was higher on P21 compared to that on P14 in both groups. Number of seizures with tonic–clonic features increased in pups of stressed group compared to the control group. Prenatal stress significantly caused an increase in the total score of seizure on P21.Conclusion:The effect of PS on seizure susceptibility is age-specific; the increased γ2 subunit level in the hippocampus might be, at least in part, the underlying mechanism for PS-induced augmentation of seizures in immature rats.

Hyperthermia-Induced Febrile Seizures Have Moderate and Transient Effects on Spatial Learning in Immature Rats.

The aim of this study was to characterize a novel animal model hyperthermia-induced febrile seizure and to investigate the impacts of repetitive febrile seizures on spatial learning and memory performances in immature rats. Methods. Rats were subjected to hyperthermia exposure one, two, or three times in 10-day intervals during 30 min in a water bath warmed at 45–50°C and their behaviour was monitored. Morris water maze spatial learning and memory were examined for control and treated groups. Results showed that rats subjected to 30-minute hyperthermia hot water developed rapidly myoclonic jerks and then generalized seizures. After a single hyperthermia exposure, the time for generalised tonic-clonic seizures appearance was 16.08 ± 0.60 min and it decreased gradually with repetitive exposure to reach 12.46 ± 0.39 min by the third exposure. Febrile seizures altered the spatial learning and memory abilities in Morris water maze and increased the time spent to attain the platform after one or two exposures, while after a third exposure rats exhibited the same latency compared to controls. Similar results were obtained in probe test where rats, subjected to hyperthermia for one or two episodes, spent less time in the target quadrant compared to corresponding controls. Further, when platform was moved from northwest to southwest quadrant, memory transfer test indicated that after one or two hyperthermia exposures cognitive performances were slightly altered, while after a third exposure the latency to escape increased significantly compared to untreated group. It was concluded that 30 min of hyperthermia hot water was sufficient to induce febrile seizures in immature rats and an increase of susceptibility was observed with repetitive hyperthermia exposure. Hyperthermia treatment impaired cognitive performances but the effects were mostly transient and moderate.

P2X7 receptor inhibition interrupts the progression of seizures in immature rats and reduces hippocampal damage.

Early-life seizures, particularly when prolonged, may be harmful to the brain. Current pharmacotherapy is often ineffective; therefore, novel neuro- and/or glio-transmitter systems should be explored for targeting. The P2X7 receptor is a cation-permeable channel with trophic and excitability effects on neurons and glia which is activated by high amounts of ATP that may be released in the setting of injury after severe seizures. Here, we tested the effects of A-438079, a potent and selective P2X7 receptor antagonist in a lesional model of early-life status epilepticus. Seizures were induced by intra-amygdala kainic acid in 10-day-old rat pups. Electrographic seizure severity, changes to P2X7 receptor expression, inflammatory responses and histological effects were evaluated. Seizures induced by intra-amygdala kainic acid increased levels of P2X7 receptor protein and interleukin-1β and caused significant cell death within the ipsilateral hippocampus. A-438079 rapidly reached the brain following systemic injection in P10 rats. Intraperitoneal injection of A-438079 (5 and 15 mg/kg) 60 min after triggering seizures reduced seizure severity and neuronal death within the hippocampus. A-438079 had superior neuroprotective effects compared with an equally seizure-suppressive dose of phenobarbital (25 mg/kg). These results suggest P2X7 receptor antagonists may be suitable as frontline or adjunctive treatments of pediatric status epilepticus or other early-life seizures, particularly when associated with brain damage.

Derivatives of valproic acid are active against pentetrazol-induced seizures in immature rats

Propylisopropyl acetamide (PID) and valnoctamide (VCD) are two CNS-active constitutional isomers of valproic acid (VPA) corresponding amide (and prodrug) valpromide. VPA is a major antiepileptic drug (AED) used also in children. Consequently, the purpose of the current study was to see if PID, VCD and two of VCD stereoisomers are active also in juvenile anticonvulsant animal seizure models. Rat pups 7, 12, 18 and 25 days old were pretreated with PID, VCD or the VCD stereoisomers (2S,3S)-VCD, and (2R,3S)-VCD and 30 min later pentetrazol (100mg/kg s.c.) was administered. The incidence of seizures, their expression pattern and their latencies were registered and the severity was expressed by means of a five-point scale. All four tested compounds exhibited anticonvulsant activity against generalized tonic-clonic seizures. Lower doses suppressed specifically the tonic phase in 7-, 12- and 18-day-old rats, while higher doses abolished both phases of generalized seizures. This effect was most pronounced in 12-day-old rats. Twenty-five-day-old rats exhibited suppression of the entire pattern of generalized seizures. There were no significant differences among the drugs used. The CNS-active amide derivatives of VPA, VCD (racemate or individual stereoisomers) and PID exhibit potent anticonvulsant activity against generalized convulsive seizures in developing rats. The majority of these developmental effects are quantitative; while a specific selective action on the tonic phase of generalized seizures is the main qualitative change found in our study.

Positive Allosteric Modulator of mGluR4 PHCCC Exhibits Proconvulsant Action in Three Models of Epileptic Seizures in Immature Rats

The activation of metabotropic glutamate receptors subtype 4 (mGluR4) potentiates models of absence seizures in adult rats. These seizures are age-dependent, but data concerning the role of mGluR4 in immature brain is insufficient. N-phenyl-7-(hydroxyimino)cyclopropa[b]chromen-1acarboxamide (PHCCC), which is a positive allosteric modulator of these receptors, was used in three different models of seizures in immature rats: 1) convulsions induced by high doses of pentetrazol (PTZ; a model of generalised tonic-clonic seizures); 2) rhythmic electro-encephalographic (EEG) activity induced by low doses of PTZ (a model of absence seizures); and 3) electrically elicited cortical afterdischarges (ADs, a model of myoclonic seizures). We administered four doses of PHCCC (1, 3, 10 and 20 mg/kg) in PTZ-induced convulsions and two doses (3 and 10 mg/kg) in the two electrophysiological models of freely moving rats with implanted electrodes. Every dose and age group consisted from 8 to 10 rats. PTZ-elicited convulsions were not significantly influenced by PHCCC. In contrast, PHCCC potentiated the effect of a subconvulsant dose (60 mg/kg) of PTZ. The 10-mg/kg dose of PHCCC significantly prolonged the duration of PTZ-induced rhythmic activity episodes and shortened the intervals between individual episodes in 25-day-old rats (P25). In contrast, this potentiation was not seen in P18 rats. Cortical ADs were significantly prolonged with repeated stimulations by both doses of PHCCC in P12 and P18 animals. P25 rats exhibited only slightly longer AD durations. In conclusion, we did not find any anticonvulsant effect of PHCCC. On the contrary, proconvulsant action was demonstrated in all three models in immature rats.

Anticonvulsive Effect of Paeoniflorin on Experimental Febrile Seizures in Immature Rats: Possible Application for Febrile Seizures in Children

Febrile seizures (FS) is the most common convulsive disorder in children, but there have been no clinical and experimental studies of the possible treatment of FS with herbal medicines, which are widely used in Asian countries. Paeoniflorin (PF) is a major bioactive component of Radix Paeoniae alba, and PF-containing herbal medicines have been used for neuromuscular, neuropsychiatric, and neurodegenerative disorders. In this study, we analyzed the anticonvulsive effect of PF and Keishikashakuyaku-to (KS; a PF-containing herbal medicine) for hyperthermia-induced seizures in immature rats as a model of human FS. When immature (P5) male rats were administered PF or KS for 10 days, hyperthermia-induced seizures were significantly suppressed compared to control rats. In cultured hippocampal neurons, PF suppressed glutamate-induced elevation of intracellular Ca2+ ([Ca2+]i), glutamate receptor-mediated membrane depolarization, and glutamate-induced neuronal death. In addition, PF partially suppressed the elevation in [Ca2+]i induced by activation of the metabotropic glutamate receptor 5 (mGluR5), but not that mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors. However, PF did not affect production or release of γ-aminobutyric acid (GABA) in hippocampal neurons. These results suggest that PF or PF-containing herbal medicines exert anticonvulsive effects at least in part by preventing mGluR5-dependent [Ca2+]i elevations. Thus, it could be a possible candidate for the treatment of FS in children.

Loss of dendritic inhibition in the hippocampus after repeated early-life hyperthermic seizures in rats

Seizures are relatively common in children and are a risk factor for subsequent temporal lobe epilepsy. To investigate whether early-life seizures themselves are detrimental to the proper function of the adult brain, we studied whether dendritic excitation and inhibition in the hippocampus of adult rats were altered after hyperthermia-induced seizures in immature rats. In particular, we hypothesized that apical dendritic inhibition in hippocampal CA1 pyramidal cells would be disrupted following hyperthermia-induced seizures in early life. Seizure rats were given three hyperthermia-induced seizures per day for three days from postnatal day (PND) 13 to 15; control rats were handled similarly but not heated. At PND 65-75, paired-pulse inhibition in area CA1 was evaluated under urethane anesthesia, using CA3 and medial perforant path (MPP) stimulation to excite the proximal and distal apical-dendrites, respectively, and the evoked field potentials were analyzed by current source density. There was no difference in the CA1 response to single-pulse stimulation of CA3 or MPP. In control rats, a high-intensity CA3 stimulus inhibited a subsequent MPP-evoked CA1 distal dendritic excitatory sink, and the inhibition at 150-200 ms was blocked by a GABA(B) receptor antagonist. Seizure as compared to control rats showed a decrease in a CA3-evoked inhibition of the CA1 distal dendritic excitation, 30-400 ms after the CA3 stimulus. In addition, seizure as compared to control rats showed a reduced early (20-80 ms) inhibition of a CA1 mid-apical dendritic sink following paired-pulse CA3 stimulation. In conclusion, long-term alterations in dendritic inhibition in CA1 were found following early-life seizures.

Models of Epileptic Seizures in Immature Rats

Models of basic types of epileptic seizures are elaborated not only in adult but also in immature rodents. It is important because at least half of human epilepsies starts during infancy and childhood. This paper presents a review of chemically and electrically induced models of generalized convulsive and nonconvulsive (absence) seizures as well as models of partial simple (neocortical) and complex (limbic) seizures in immature rats. These models can also serve as a tool for study the development of central nervous system and motor abilities because the level of maturation is reflected in seizure semiology. Age-dependent models of epileptic seizures (absences and flexion seizures) are discussed. Models of seizures in immature animals should be used for testing of potential antiepileptic drugs.

GABA-B receptor antagonist CGP 35348 interferes with an arrest of cortical epileptic afterdischarges in developing rats

Epileptic seizures activate not only excitatory but also inhibitory systems what results in an arrest of seizures. Our recent data indicate that GABAergic inhibition plays an important role in this process in cortically elicited seizures. We started to study the role of GABA-B receptors in cortical epileptic afterdischarges (ADs) in immature rats 12, 18 and 25 days old with implanted electrodes. Low-frequency stimulation of sensorimotor cortical area was repeated with increasing intensities of stimulation current. Thresholds for movements directly elicited by stimulation, for spike-and-wave type of AD, for clonic seizures accompanying this type of ADs and for transition into limbic type of AD were decreased by the 200mg/kg dose of a GABA-B receptor antagonist CGP35348 in all three age groups. Duration of ADs was markedly increased by 50, 100 as well as 200mg/kg dose of CGP35348. The effects were best expressed in 18-day-old rats. To conclude, GABA-B receptors play an important role in generation and especially in arrest of cortical seizures in immature rats.

Anticonvulsant action of 2-chloroadenosine against pentetrazol-induced seizures in immature rats is due to activation of A1 adenosine receptors

Potentiation of adenosinergic inhibitory modulation is one of possible strategies to develop new antiepileptic drugs. Nonspecific receptor agonist 2-chloroadenosine was tested against pentetrazol-induced convulsions in immature (7, 12, 18 and 25days old) and adult rats. Doses of 1-15mg/kg i.p. suppressed tonic phase of generalized tonic-clonic seizures (GTCS) in the two youngest groups, whereas GTCS were abolished in older rats. Minimal clonic seizures in 18-day and older rats were suppressed by high doses of 2-chloroadenosine. The role of A1 and A2A adenosine receptors was studied in 12- and 25-day-old rats. Action of an agonist of A1 receptors CCPA is similar to that of 2-chloroadenosine. An agonist of A2A receptors CGS 21680 exhibits an anticonvulsant action only in the dose-inducing catalepsy; an A2A antagonist ZM 241385 moderately suppressed tonic phase of GTCS only in 12-day-old animals. Anticonvulsant action of adenosine agonists is due to their effects on A1 receptors.

Anticonvulsive effect of vitamin C on pentylenetetrazol-induced seizures in immature rats

Vitamin C helps to prevent brain oxidative stress and participate in the synthesis of progesterone. It also possesses a progesterone-like effect and acts synergistically with progesterone on the brain. Progesterone and its metabolites, but also vitamin C have been associated with anticonvulsant effects. We evaluated the progesterone concentration 30 min and 24 h after the last administration of vitamin C (500 mg/kg, i.p. for five days). We also evaluated how vitamin C altered pentylenetetrazol (PTZ)-induced seizures by measuring the onset latency of seizures, percentage of incidence and mortality as well as amino acid levels after seizures. Vitamin C treatment alone increased basal progesterone concentrations to 531% after 30 min compared to 253% after 24 h. Furthermore, vitamin C significantly increased the latency to the first myoclonic, clonic and tonic seizure induced by PTZ (80 mg/kg, i.p.) and decreased the percentage of incidence of clonic and tonic seizures as well as the mortality rate. Changes in tissue concentration of amino acids were primarily observed at 24 h after vitamin C treatment. Our results suggest that vitamin C together with progesterone and/or its metabolites are involved in the protection against PTZ-induced seizures in immature rats.

Aneseizure: Is the Neonatal Brain Asleep?

Aneseizure: Is the Neonatal Brain Asleep?

Similar Effects of Lamotrigine and Phenytoin against Cortical Epileptic Foci in Immature Rats

Action of antiepileptic drugs in immature brain may differ from that in adult brain. The aim of our study was to study an anticonvulsant action of lamotrigine and phenytoin, i.e. two drugs active against partial seizures in adult experimental animals as well as human patients, in a model of simple partial seizures in immature rats. Epileptic foci were induced by local application of bicuculline methiodide on sensorimotor cortical area of 12-day-old rat pups. The animals were pretreated with lamotrigine (LTG, 10 or 20 mg/kg i.p.) or phenytoin (PHT, 15, 30 or 60 mg/kg i.p.). Control rats for LTG received saline, controls for PHT solvent composed of propyleneglycol, ethanol and water. Influence of either drug on interictal activity was negligible. High doses of both LTG and PHT suppressed the transition into ictal phases and shortened the duration of persisting seizures. The tricomponent solvent exhibited moderate activity against ictal activity if compared with saline controls. The two drugs exhibited similar action in our model, i.e. the suppression of secondary generalization from epileptic focus. This action is comparable to that described for human patients and adult experimental animals. In favor of lamotrigine speaks the absence of serious side effects.

Anticonvulsant doses of ganaxolone do not compromise motor performance in immature rats

Neuroactive steroids that function as positive modulators of GABA-A receptors are potential anticonvulsant drugs. We previously demonstrated that ganaxolone is effective against pentetrazol-induced motor seizures in immature rats. In the present study, we examined the effects of ganaxolone in another model, cortical epileptic afterdischarges (ADs). The possible side effects of ganaxolone were studied in rats 12, 18, and 25 days of age following the implantation of epidural electrodes. Low-frequency stimulation of the sensorimotor cortical area elicited ADs characterized by a spike-and-wave rhythm and clonic seizures. Ganaxolone (5, 10, 20, or 40 mg/kg) was administered intraperitoneally after the first AD and stimulation was repeated five more times. The highest dose of ganaxolone (40 mg/kg) suppressed progressive prolongation of ADs in 25-day-old rats and postponed it in 12-day-old rats. No significant effect was observed in 18-day-old animals. Movements during stimulation and clonic seizures accompanying ADs were not affected by ganaxolone. Ganaxolone at doses of 20 and 40 mg/kg had no significant effect on motor function, such as surface righting, negative geotaxis, wire mesh ascending, and bar holding. After administration of 40 mg/kg ganaxolone to 18- and 25-day-old rats, spontaneous locomotion in the open field tended to decrease. Doses of ganaxolone with a moderate anticonvulsant effect in the present model did not seriously compromise motor performance.

Hyperthermic seizures and hyperthermia in immature rats modify the subsequent pentylenetetrazole-induced seizures

It has been described that febrile seizures during infancy increase risk of subsequent non-febrile seizures during the adulthood. However, latency period between febrile seizure and the onset of the first spontaneous seizure has not been evaluated. The present study was designed to investigate the susceptibility to subsequent seizures in immature rats that had experienced early-life hyperthermic seizures and before they achieved the adult age. The results were compared with those induced by hyperthermia alone. Pentylenetetrazol (PTZ) was applied 24 h or 20 days after hyperthermic seizures or hyperthermia were induced in 10-day-old rats by a regulated stream of moderately heated air. One day after hyperthermic seizures or hyperthermia, animals demonstrated enhanced latency to the PTZ-induced myoclonic (88% and 53%, respectively), clonic (60% and 60%, respectively) and tonic seizures (233% and 659%, respectively). The incidence of myoclonic and clonic seizures was similar to that in control group (100%). However, hyperthermic seizures reduced (50%) the incidence of tonic seizures. Twenty days after hyperthermic seizures there was an augmented latency to tonic seizures (123%) and reduced incidence for all the PTZ-induced seizures (71% myoclonic; 71% clonic seizures; 57% tonic seizures) when compared with control group (100%). In contrast, hyperthermia enhanced only the latency to myoclonic (133%) and clonic seizures (659%). Our data indicate that hyperthermic seizures or hyperthermia induces a protective effect against PTZ-induced seizures during a latency period. A possible involvement of γ-aminobutyric acid (GABA) system is discussed.

Effects of temperature elevation on neuronal inhibition in hippocampal neurons of immature and mature rats

Febrile seizures are the most common seizure type in children, and hyperthermia may contribute to seizure generation during fever. We have previously demonstrated that hyperthermia suppressed gamma-aminobutyric acid (GABA)-ergic synaptic transmission in CA1 neurons of immature rats. However, whether this suppression is age-dependent is unknown. Moreover, it is unclear whether hyperthermia has differential effects on neuronal inhibition in CA1 pyramidal cells (PCs) and dentate gyrus granule cells (GCs). In this study, we investigated the effects of hyperthermia on GABA(A) and GABA(B) receptor-mediated inhibitory postsynaptic currents (IPSCs) in CA1 and DG neurons from immature (11-17 days old) and mature (6-8 weeks old) rats using whole-cell recordings in vitro. In immature rats, hyperthermia decreased the peak amplitude of GABA(A) receptor-mediated IPSCs (GABA(A) IPSCs) in PCs but not in GCs. However, hyperthermia decreased the decay time constant of GABA(A) IPSCs to a similar extent in both PCs and GCs. In mature rats, hyperthermia decreased the peak amplitude but not the decay time constant of GABA(A) IPSCs in both PCs and GCs. Hyperthermia decreased charge transfer (area) of the GABA(A) IPSC of PCs more in immature than in mature rats. In contrast, hyperthermia decreased the GABA(B) receptor-mediated IPSCs to the same degree in immature and mature rats, for either CA1 or DG neurons. Because the hippocampus has been found to be involved in hyperthermia-induced behavioral seizures in immature rats, we suggest that the higher sensitivity of CA1 inhibitory synaptic function to hyperthermia in immature compared with mature rats might partially explain the higher susceptibility for febrile seizures in immature animals.

Posttreatment with group II metabotropic glutamate receptor agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate is only weakly effective on seizures in immature rats

The present study has examined the anticonvulsant and neuroprotective effect of 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC), a selective agonist for group II metabotropic glutamate receptors (mGluRs) when given 10–15 min after the onset of seizures induced in 12-day-old rats by bilateral icv infusion of dl-homocysteic acid ( dl-HCA, 600 nmol/side). For biochemical analyses, rat pups were sacrificed during generalized clonic–tonic seizures, ∼ 45–50 min after infusion of dl-HCA. Comparable time intervals were used for sacrificing the animals which received 2R,4R-APDC (0.05 nmol/side) or saline. The severity of seizures was influenced only slightly when the agonist was given after the onset of seizures, as evaluated both from the behavioral symptoms and from EEG recordings. A tendency to lower number and a shorter duration of seizures was outlined in animals posttreated with 2R,4R-APDC, but the differences did not reach the level of statistical significance. Cortical energy metabolite changes which normally accompany seizures in immature rats (large decrease of glucose and glycogen and a marked rise of lactate) were ameliorated only partially. The neuroprotective effect of 2R,4R-APDC was evaluated after 24 h and 6 days of survival following dl-HCA-induced seizures. Massive neuronal degeneration in many brain regions, mainly in the hippocampus and thalamus, following infusion of dl-HCA alone was only partially attenuated after 2R,4R-APDC posttreatment. The present findings clearly indicate that both anticonvulsant and neuroprotective effect of 2R,4R-APDC against dl-HCA-induced seizures is substantially diminished when the agonist is given after the onset of seizures as compared with its efficacy after the pretreatment (Exp.Neurol.192, 420–436, 2005).

Intrahippocampal Injection of Endothelin‐1: A New Model of Ischemia‐induced Seizures in Immature Rats

The goal of this study was to develop a new model of ischemia-induced seizures in immature rats using injection of vasoconstrictor Endothelin-1 (ET-1) into the brain. ET-1 (10, 20, or 40 pmol) was infused into the left dorsal hippocampus of freely moving Wistar rats 12 (P12) and 25 (P25) days old. Animals were then video/EEG-monitored for 100 min and monitoring was repeated 22 h later. Parameters of electrographic seizures (frequency and mean duration) as well as pattern of their behavioral correlates were evaluated. The pattern of behavioral seizures was used to develop model-specific scoring system. Cresyl violet and Fluoro Jade-B-staining were used to evaluate brain damage. Extension of the lesion was correlated with seizure severity. After ET-1-injection, seizures occurred in 83-100% animals of all age-and-dose groups and persisted for 24 h except P12 rats with 10 pmol. There were no differences in average seizure duration (18-40 s) or seizure frequency (3-7 seizures/100 min) among individual dose-groups. Between the 1st and 2nd observation period, total seizure duration decreased in 71% of P12 and 47% of P25 rats. Electrographic seizure activity was most frequently accompanied by clonus, incidence of more severe convulsions (barrel rolling or generalized clonic seizures) increased with dose of ET-1. Morphologic examination did not reveal any dose-related difference in damage severity, hippocampal damage was however more extensive in P12 compared to P25 animals. Seizure severity correlated positively with severity of the damage in both age groups. Our study presents focal injection of ET-1 into the brain as a new and practical model of ischemia-induced seizures in immature rats.