Do stereoisomers of homocysteic acid exhibit different convulsant action in immature rats?

Mechanism of ictogenesis of D- and L-stereroisomers of homocysteic acid was studied in 12-day-old rats by means of antagonists of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. There was no qualitative difference between the two stereoisomers in generation of emprosthotonic (flexion) as well as generalized tonic-clonic seizures. Moderate differences were observed in the first, nonconvulsive effects of the two isomers. As generation of the two types of seizures is concerned, NMDA and AMPA participate in generalized tonic-clonic seizures whereas NMDA receptors play a dominant role in generation of flexion seizures.

Anorexigenic effect of cholecystokinin is lost but that of CART (Cocaine and Amphetamine Regulated Transcript) peptide is preserved in monosodium glutamate obese mice.

Monosodium glutamate (MSG) treatment of neonatal mice results in a selective damage to the arcuate nucleus (ARC) and development of obesity with increased adiposity at sustained body weight in the adulthood. Feeding pattern of the MSG obese mice is unusual. Our previous results showed that after 24-h fasting, MSG mice consumed negligible amount of food in several hours and therefore, it was impossible to register the effect of peptides attenuating food intake such as cholecystokinin (CCK) or cocaine- and amphetamine-regulated transcript (CART) peptide. To overcome this problem, two findings were used: firstly, orexigenic effect of neuropeptide Y (NPY) was attenuated both by CCK or CART peptide in lean fed mice and secondly, orexigenic effect of NPY was preserved in fed rats with MSG obesity. In this study, short-term food intake in fed lean and MSG obese C57BL/6 male mice was measured after simultaneous central administration of orexigenic NPY with either CART peptide or peripherally administered CCK. Anorexigenic action of exogenous CART peptide was preserved in MSG obese mice. On the other hand, satiety effect of exogenous CCK was completely lost in MSG obese mice. In conclusion, effective leptin signaling in ARC is necessary for satiety effect of CCK.

Anticonvulsant action of allopregnanolone in immature rats.

Anticonvulsant activity of allopregnanolone, a neurosteroid allosterically modulating GABA(A) receptor was tested in a model of motor seizures elicited by pentetrazol in immature rats. Rats 7, 12, 18, 25 or 90 days old were pretreated with allopregnanolone in doses from 5 to 40 mg/kg i.p. and 15 min later pentetrazol was injected subcutaneously in a dose of 100 mg/kg. Rats were observed in isolation for 30 min. Allopregnanolone dose-dependently suppressed both generalized tonic-clonic and minimal clonic seizures with the highest efficacy in 12-day-old rats. Anticonvulsant action was least expressed in adult animals. Duration of anticonvulsant action tested after a dose of 20 mg/kg in 12- and 90-day-old rats demonstrated markedly longer effects in young rats. Allopregnanolone compromised motor performance of rats but duration of this unwanted effect in 12-day-old rats was shorter than duration of anticonvulsant action. This difference can be important for possible clinical use of neurosteroids.

Action of two neuroactive steroids against motor seizures induced by pentetrazol in rats during ontogeny.

The anticonvulsant action of two neuroactive steroids, 3alpha-hydroxy-5beta-pregnan-20-one (pregnanolone) and triethylammonium 3 alpha-hydroxy-20-oxo-5 alpha-pregnan-21-yl hydrogensuccinate (THDOC-conjugate), was tested against motor seizures induced by pentetrazol in immature rats. Five age groups (7, 12, 18 and 25 days old and adult rats) were pretreated with the steroids in doses from 2.5 to 40 mg/kg i.p. Twenty minutes later pentetrazol (100 mg/kg s.c.) was administered. Minimal seizures (clonic seizures of head and forelimb muscles with preserved righting ability) could be induced in the three older age groups. They were suppressed by pregnanolone in all these tested groups (this effect was best expressed in 18-day-old rats and decreased with age), whereas significant changes in THDOC-conjugate-pretreated animals appeared only in 18-day-old rats. Generalized tonic-clonic seizures were suppressed by both neuroactive steroids in all age groups, this effect being more marked with pregnanolone and again decreased with age. The 7- and 12-day-old rats exhibited higher sensitivity of the tonic phase so that generalized clonic seizures were observed. Duration of the effect was studied in 12- and 25-day-old animals; it was substantially shorter in the older rats than in 12-day-old animals. Both drugs exhibited an anticonvulsant action in developing rats but, unfortunately, their effect was only shortlasting.

Neuroprotective effect of (R, S)-4-phosphonophenylglycine against neuronal damage associated with homocysteic acid-induced seizures in immature rats.

Incidence of human epilepsy in infants and children is high and prolonged seizures in the early developmental period can cause brain damage and lead to serious consequences later in the life. The present study was aimed to investigate potential protective effect of (R, S)-4-phosphonophenylglycine ((R, S)-PPG), a potent and selective group III mGluR agonist, on brain damage associated with homocysteic acid-induced seizures in immature 12-day-old rats. This compound does not exhibit any proconvulsive effect. Moreover, (R, S)-PPG was shown to protect NMDA and quinolinic acid-induced lesions in rats. Seizures were induced by bilateral intracerebroventricular (i.c.v.) infusion of homocysteic acid (DL-HCA, 600 nmol/side). (R, S)-PPG was given by bilateral i.c.v. infusions (5 nmol/side) at 15- to 20-min time intervals prior to administration of DL-HCA. After 1 or 6 days of survival, animals in all experimental groups (13-day-old and 18-day-old) were perfused transcardially under deep ether anaesthesia with heparinized normal saline and subsequently with the fixation solution (4% paraformaldehyde in the phosphate buffer, pH 7.4, both solutions at room temperature). Two histological methods were used in our study. Fluoro-Jade B dye is an anionic fluorescein derivative useful for the histological staining of neurons undergoing degeneration and staining with bis-benzimide (Hoechst 33342) was used to detect apoptotic cells according nuclei with condensed and/or fragmented DNA. Animals perfused 1 day after the treatment (13-day-old): After only (R, S)-PPG application, no obvious pathological changes were found. After only DL-HCA application, distinct destruction of the hippocampal region both in the dorsal and ventral hippocampus was observed. Particularly affected were cells in the CA1 and CA3 regions. In addition, neurons with segmented or fragmented nuclei were found in the granule cell layer of the dentate gyrus. (R, S)-PPG + DL-HCA administration resulted in a lower number of Fluoro-Jade B positive cells. All areas of the hippocampus were protected by (R, S)-PPG pre-treatment. Animals perfused 6 days after the treatment (18-day-old): In the group where only (R, S)-PPG has been applied, no obvious pathological changes were found in the hippocampal area. After only DL-HCA administration almost complete destruction of the hippocampal region both in the dorsal and ventral hippocampus was observed. Particularly affected were the cells in the CA1 and CA3 regions, granule cells of the dentate gyrus and many interneurons in all hippocampal areas. (R, S)-PPG + DL-HCA administration resulted in lower number of Fluoro-Jade B positive cells. All areas of the hippocampus have been protected by (R, S)-PPG pre-treatment. In conclusion, the present data support the hypothesis that (R, S)-PPG can have a beneficial effect in those disorders where excitotoxicity is one of the dominant pathogenetic mechanisms.

[Characterization of Haemophilus influenzae strains using multilocus sequencing]. / Charakterizace kmenu Haemophilus influenzae metodou multilokusové sekvenacní typizace.

First results of multilocus sequence typing (MLST) of Haemophilus influenzae strains are presented. MLST of 28 H. influenzae strains isolated from patients with invasive diseases in the Czech Republic is indicative of clonal homogeneity of these strains: 22 out of 26 H. influenzae b strains tested were of the same sequence type, ST-6. Four strains were of two sequence types newly described in this study: ST-83 (3 strains) and ST-84 (1 strain). Two nontypeable H. influenzae strains were assigned to sequence types other than ST-6: ST-3 and ST-85 newly described in this study. First MLST results show ST-6 to be typical of H. influenzae b isolated from patients with invasive diseases in the Czech Republic. The sequence types newly described in this study, i.e. ST-83, ST-84 and ST-85, were submitted to the worldwide H. influenzae MLST database (http://haemophilus.mlst.net).

[Study of long-term and multiple carriage of Neisseria meningitidis in a healthy population using molecular biology methods]. / Studie dlouhodobosti a mnohocetnosti nosicství Neisseria meningitidis ve zdravé populaci molekulárními biologickými metodami.

The aim of the study was to investigate the long-term duration and multiple carriage of Neisseria meningitidis in a healthy population. In this prospective study, 206 students at the age of 15 to 19 years were monitored from October 2002 to March 2003. Nasopharyngeal and laryngeal swabs were sampled in one-month intervals and cultured on a selective medium. All colonies detected in primary culture were saved for the study, a maximum of 20 colonies in cases of massive growth. A total of 1,242 isolates were obtained, all of them being examined by a molecular biology method RAPD (randomly amplified polymorphic DNA analysis). By other methods (determination of phenotype by slide agglutination and whole-cell ELISA test, the determination of sequence type, ST by multilocus sequence typing, testing of susceptibility to antibiotics) were always tested the first isolates from individual carriers and isolates from the same carrier with different RAPD characteristics, being 35 altogether. There were thirty three carriers of N. meningitidis detected among the 206 students (16%). The carriage of N. meningitidis was of long-term duration. The study of strains of N. meningitidis with molecular biology methods made it clear that the carrier population of meningococci is heterogeneous. The population of carrier meningococci was of clonal character and mostly non-virulent ST-complexes were detected. Multiple carriage of different clones of N. meningitidis is rare and usually of short-term duration. The colonization of upper respiratory tract by a single clone of N. meningitidis does not protect from colonization by other clone.

Lithium/pilocarpine status epilepticus-induced neuropathology of piriform cortex and adjoining structures in rats is age-dependent.

Distribution of LiCl/pilocarpine status epilepticus-induced neuronal damage was studied in the piriform cortex and in adjoining structures in 12-day-old, 25-day-old and adult rats. No distinct structural and neuronal alterations were detected in the basal telencephalon in 12-day-old rats surviving status epilepticus (SE) for one week or two months. In 25-day-old rats a decrease in Nissl staining was evident. There was also cell loss and gliosis in the caudal 2/3 of the piriform cortex, in the superficial amygdaloid nuclei, in the dorsal and ventral endopiriform nucleus and in the rostrolateral part of the entorhinal cortical area. In adult animals, the topography of neuropathological changes in the basal telencephalon was comparable to those in 25-day-old rats. The damage in the caudal 2/3 or caudal half of the piriform cortex in adult rats with survival times one week or two months was characterized by a marked loss of neurons and striking glial infiltration. The thickness of the piriform cortex and superficial amygdaloid nuclei was significantly reduced. In 25-day-old and in adult animals the sublayer IIb and layer III of the piriform cortex was more affected, while sublayer IIa was less damaged. Parvalbumin (PV) immunocytochemistry revealed a significant decrease in the number of PV-immunoreactive neurons in the rostral piriform cortex and in the dorsal claustrum in animals surviving for two months.

Does vigabatrin possess an anticonvulsant action against pentylenetetrazol-induced seizures in developing rats?

Anticonvulsant action of vigabatrin (300, 600, 900 and/or 1200 mg/kg i.p.), an inhibitor of GABA-transaminase, was studied in a model of motor sezures elicited by pentylenetetrazol. Five age groups of rats (7, 12, 18, 25 and 90 days old) received a s.c. injection of pentylenetetrazol 4, 6 and/or 24 hours after vigabatrin administration. The incidence of minimal, predominantly clonic seizures was not changed in any age group, but their latencies were prolonged in 18- and 25-day-old rats. Generalized tonic-clonic seizures were influenced in a more complex manner. Incidence of these seizures was decreased in 7-day-old rat pups 24 hours after vigabatrin administration. Higher doses of vigabatrin exhibited a similar effect in adult rats at all intervals studied. Specific suppression or at least restriction of the tonic phase was observed in all groups of immature rats, the effect was more marked 24 hours after vigabatrin than at shorter intervals. The anticonvulsant action of vigabatrin, which could be demonstrated mainly against generalized tonic-clonic seizures, varies markedly during development.

Effects of classical antiepileptics on thresholds for phenomena induced by cortical stimulation in rats.

Our aim was to study the effects of phenobarbital, phenytoin and ethosuximide on epileptic afterdischarges induced by cortical stimulation in rats. Fifteen-second series of low-frequency (8 Hz) rhythmic stimulation of the sensorimotor cortex were applied in rats with chronically implanted electrodes. Intervals between the stimulation series were at least 10 min and intensity was increased in a step-wise manner. Threshold current intensities were estimated for movements directly induced by stimulation, epileptic afterdischarges of the spike-and-wave type, clonic seizures accompanying this type of afterdischarge and transition into the limbic type of afterdischarge. Phenobarbital, phenytoin and ethosuximide were administered intraperitoneally before the first stimulation series. Phenobarbital (20, 40 and 80 mg kg(-1)) significantly increased the thresholds for the first three phenomena in a dose-dependent manner. Transition into the limbic afterdischarge was influenced only by the highest dose. Phenytoin (60 mg kg(-1)) only increased the thresholds insignificantly and ethosuximide (125 mg kg(-1)) was ineffective. We concluded that our model is useful for testing anticonvulsant effects. Results with three antiepileptic drugs correspond with their efficacy against myoclonic seizures in man.

Are acute changes after status epilepticus in immature rats persistent?

Early consequences of lithium-pilocarpine convulsive status epilepticus (SE) were studied six days after this status had been induced in rat pups at the age of either 12 or 25 days. Studies of spontaneous EEG activity demonstrated the presence of epileptic phenomena (isolated spikes) in both hippocampus and cortex (cortical spikes were more expressed in the older group). There were no marked behavioral correlates of spikes and transition into the ictal phase was exceptional. The motor performance on a rotorod and a horizontal bar was the same in experimental and control rats of both ages. Behavior in the open field was changed in a reverse manner in the two age groups: the locomotor activity of rats with induced seizures at the age of 12 days was significantly lower than that of their control siblings, whereas animals undergoing status at the age of 25 days were hyperactive. In addition, they also exhibited increased exploratory activity (rearing) and their habituation to the open field was deranged. Nissl-stained brain sections demonstrated extensive brain damage in the older group in contrast to the negative findings in younger animals. EEG, behavioral and morphological changes induced by status epilepticus in developing rats persisted for 6 days after the status. They markedly differed according to the age of animals.

Dynamic changes of status epilepticus-induced neuronal degeneration in the mediodorsal nucleus of the thalamus during postnatal development of the rat.

PURPOSE: Status epilepticus (SE) was previously found to induce damage in the mediodorsal nucleus of the thalamus (MD) in both adult and immature rats. This study was designed to describe age-related changes of SE-induced neuronal degeneration in this part of the brain. METHODS: SE was induced by LiCl/pilocarpine in five age groups of rats (P12-P25). Distribution of degenerating neurons was studied at various time intervals from 4 h up to 1 week using Fluoro Jade B (FJB) staining. For P12 and P25 rats, an interval of 3 months was added. RESULTS: Damaged neurons were found in all age groups during a 1-week period after SE. Patterns of neuronal degeneration, however, changed in an age-related manner. In animals at P12 and P15, FJB-labeled neurons were located in the central and lateral segment of the MD. In the P18 group, degenerating neurons occurred in all three segments of the MD, with a prevalence in central and lateral subdivisions. In contrast, in P21 and P25 rats, FJB-labeled neurons were predominantly located in the central and medial segments. Degenerating neurons were still present 3 months after SE in the medial segment in P25 animals, whereas no labeled neurons were detected in the P12 group at this time. CONCLUSIONS: Our data demonstrate that the pattern of neuronal degeneration in MD is mainly related to age at SE onset. In addition to damage occurring during the acute phase of SE, a population of degenerating neurons was detected in P25 animals during the chronic period 3 months after SE.

Interaction of excitatory amino acid agonists with cortical afterdischarges in developing rats.

PURPOSE: To determine the role of excitatory amino acids (EAAs) in genesis of two types of epileptic afterdischarges. METHODS: Cortical stimulation and recording electrodes were implanted in 12-, 18-, and 25-day-old rats. Epileptic afterdischarges were induced by rhythmic stimulation of sensorimotor cortex. The stimulation was repeated 6 times with 20-min intervals. Ten minutes after the first afterdischarge, N-methyl-d-aspartate, homocysteine, or kainic acid was injected. The doses were chosen individually for different age groups to be subconvulsive. Type and duration of afterdischarges as well as type and severity of motor correlates were evaluated. RESULTS: N-methyl-d-aspartate prolonged afterdischarges only in 12-day-old rats, whereas two other drugs did it in all age groups. Motor correlates of afterdischarges were changed to flexion seizures in 12-day-old rats after N-methyl-d-aspartate and homocysteine; in 25-day-old rats homocysteine led to generalized tonic-clonic seizures (i.e., both patterns seen after substantially higher doses of these drugs in nonstimulated rats). Seizures lasted tens of minutes. Kainic acid did not change the motor pattern in any age group, but nonconvulsive EEG seizures were recorded in the interstimulation periods mainly in 18- and 25-day-old rats. Increased transition into the limbic type of afterdischarges appeared only after homocysteine in 18- and 25-day-old rats. CONCLUSIONS: A mutual potentiation of epileptic phenomena was induced by two agents. The actions of N-methyl-d-aspartate and kainic acid differ in all age groups; the effects of homocysteine were identical with those of N-methyl-d-aspartate in 12-day-old rats but not later. Only homocysteine augmented transition into the limbic type of afterdischarges.

Attenuation of seizures induced by homocysteic acid in immature rats by metabotropic glutamate group II and group III receptor agonists.

Previous studies demonstrated that selected agonists for metabotropic glutamate group II and group III receptors can provide protection against seizures in adult animals. The present study has examined the potential effect of some of these compounds on seizures induced in immature rats by intracerebroventricular infusion of DL-homocysteic acid (DL-HCA, 600 nmol/side). Rat pups were sacrificed during generalised clonic-tonic seizures, 50--60 min after infusion. Comparable time intervals were used for sacrificing the pups which had received the protective drugs. The anticonvulsant effect was evaluated according to the suppression of behavioural manifestations of seizures and the protection of energy metabolite changes which normally accompany these seizures (large decreases of glucose and glycogen, and approximately 7- to 10-fold accumulation of lactate). Partial protection was exhibited by group II mGluR agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG IV, 0.6 nmol) and this effect was abolished after pretreatment with an antagonist for group II mGluRs (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG, 100 nmol). In high doses (5--100 nmol), however, DCG IV evoked seizures which were prevented by AP7, suggesting that the convulsant effect was mediated by interaction with NMDA receptors. A pronounced anticonvulsant effect against DL-HCA-induced seizures was achieved with low doses of a highly selective group II mGluR agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC, 0.6 nmol), group II agonist and group I mGluR antagonist (S)-4-carboxy-3-hydroxyphenylglycine ((S)-4-C3HPG, 0.6 nmol) and group III mGluR agonist (RS)-1-amino-3-(phosphonomethylene) cyclobutane-carboxylic acid (32 nmol). Generalised clonic--tonic seizures were completely suppressed and the metabolic changes were markedly ameliorated, there being only a 1.5-, 2- and 2.5-fold rise of lactate, respectively. Higher doses of (S)-4-C3HPG (1--100 nmol) were, however, less anticonvulsant than low doses. The present results have confirmed that mGluRs may be considered a potential target for treatment of epilepsy.

Status epilepticus causes necrotic damage in the mediodorsal nucleus of the thalamus in immature rats.

Status epilepticus (StE) in immature rats causes long-term functional impairment. Whether this is associated with structural alterations remains controversial. The present study was designed to test the hypothesis that StE at an early age results in neuronal loss. StE was induced with lithium-pilocarpine in 12-d-old rats, and the presence of neuronal damage was investigated in the brain from 12 hr up to 1 week later using silver and Fluoro-Jade B staining techniques. Analysis of the sections indicated consistent neuronal damage in the central and lateral segments of the mediodorsal nucleus of the thalamus, which was confirmed using adjacent cresyl violet-stained preparations. The mechanism of thalamic damage (necrosis vs apoptosis) was investigated further using TUNEL, immunohistochemistry for caspase-3 and cytochrome c, and electron microscopy. Activated microglia were detected using OX-42 immunohistochemistry. The presence of silver and Fluoro-Jade B-positive degenerating neurons in the mediodorsal thalamic nucleus was associated with the appearance of OX-42-immunopositive activated microglia but not with the expression of markers of programmed cell death, caspase-3, or cytochrome c. Electron microscopy revealed necrosis of the ultrastructure of damaged neurons, providing further evidence that the mechanism of StE-induced damage in the mediodorsal thalamic nucleus at postnatal day 12 is necrosis rather than apoptosis. Finally, these data together with previously described functions of the medial and lateral segments of the mediodorsal thalamic nucleus suggest that some functions, such as adaptation to novelty, might become compromised after StE early in development.

Influence of convulsants on rat brain activities of alanine aminotransferase and aspartate aminotransferase.

There exist differences between 12-day-old and adult rats in the onset of seizures induced by some inhibitors of glutamate decarboxylase (GAD). The aim of study was to investigate if there are differences between both groups in activities of rat brain alanine aminotransferase (ALT) and aspartate aminotransferase (AST), the enzymes involved in glutamate metabolism, after the administration of 3-mercaptopropionic acid as specific GAD inhibitor or isoniazid as less specific general inhibitor of pyridoxal enzymes. Activities of both aminotransferases in a supernatant 20,000 g of the whole brain (containing predominantly cytosolic isoforms of enzymes) were increased at the beginning of 3-mercaptopropionic acid-induced generalized tonic-clonic seizures. At isoniazid-induced generalized tonic-clonic seizures, a significant increase in both enzyme activities was observed in adult rat brain. In the 12-day-old rat brain, ALT and AST activities reached about 40% and about 50-60% of adult control levels, respectively. In in vitro experiments, no influence of 3-mercaptopropionic acid on transaminase activities was found and an inhibitory effect of isoniazid on the enzymes was confirmed. Increased aminotransferase activities might participate in the enhanced synthesis of excitatory amino acid neurotransmitters in the nervous system, which may take a part in the initiation of epileptic seizures. Alternatively, the increased AST activity may be connected with an increased transport of NADH from the cytosol to mitochondria, while the increased ALT activity would represent the transformation of pyruvate to alanine as a consequence of increased glycolysis.

Two different anticonvulsant actions of tiagabine in developing rats.

PURPOSE: Our goal was to study the anticonvulsant action of tiagabine (TGB) at different levels of brain maturation in rats. METHODS: Wistar rats in five age groups (7, 12, 18, 25, and 90 days old) were injected intraperitoneally with TGB at doses of 0.5-32 mg/kg. Thirty minutes later, motor seizures were induced by the subcutaneous adminstration of pentylenetetrazol (PTZ) in a dose of 100 mg/kg for all of the groups except the 18-day-old rat pups, which received a 90-mg/kg dose. The incidence and latency of two types of motor seizures, minimal clonic and generalized tonic-clonic seizures (GTCSs), were evaluated, and the seizure severity was scored. The time profile of TGB action at the 8-mg/kg dose was studied in the 12-and 25-day-old rats. RESULTS: Minimal clonic seizures were reliably induced in rats 18 days old or older, and the seizures were suppressed by TGB in all of these age groups. Although TGB was very effective against this type of seizure in the 18-day-old rats, the efficacy of the drug decreased with the age of the animal. GTCSs were suppressed by TGB in the adult and 25-day-old rats, and a U-shaped dose-response curve was outlined in these two groups. The 18-and 12-day-old rat pups exhibited a selective suppression of the tonic phase of GTCSs. A mixture of these two effects was observed in the youngest group. TGB demonstrated a markedly longer action in the 12-day-old rats than in the 25-day-old rats. CONCLUSIONS: TGB exhibits anticonvulsant action against both minimal seizures and GTCSs. Ontogenetic development of these two actions is markedly different.

Anticonvulsant action of topiramate against motor seizures in developing rats.

PURPOSE: To study the anticonvulsant action of topiramate (TPM) in developing rats. METHODS: Motor seizures were elicited by administering pentylenetetrazol (100 mg/kg subcutaneously) in five age groups of Wistar rats (7, 12, 18, 25, and 90 days old). TPM was administered intraperitoneally in doses from 10 to 640 mg/kg 2 hours before pentylenetetrazol. The time course of TPM action was studied in 12- and 25-day-old rats up to 24 hours after the 160-mg/kg dose, and the incidence and pattern of seizures were evaluated. RESULTS: TPM did not influence minimal seizures (clonus of forelimb and head muscles with preserved righting ability). Generalized tonic-clonic seizures, however, were reliably changed at all developmental stages studied. The tonic phase was suppressed so that the majority of animals exhibited generalized clonic seizures (with a loss of righting reflexes). In addition, the incidence of generalized seizures was decreased after the 20-, 40-, and 80-mg/kg doses in the 7-day-old rat pups. The specific suppression of the tonic phase of generalized seizures was observed up to 12 hours in the 12-day-old rat pups. The same result was obtained over 6 hours after TPM administration in the 25-day-old animals, and with longer intervals the incidence of generalized seizures decreased in this age group. CONCLUSIONS: TPM exhibits stable anticonvulsant action against the tonic phase of generalized tonic-clonic seizures throughout development. In addition, it suppresses all phases of generalized seizures in 7-day-old rats. The anticonvulsant action of TPM lasted longer in 25-day-old than in 12-day-old rats. The two actions of TPM might be ascribed to two different mechanisms of action.

Does status epilepticus influence the motor development of immature rats?

PURPOSE: To study the effect of severe status epilepticus (SE) on the motor development of rats. METHODS: SE was induced in 12-day-old rats (P12 group) and 25-day-old rats (P25 group) using the lithium-pilocarpine model. Seizures were interrupted after 2 hours by paraldehyde with an intraperitoneal dose of 0.3 or 0.6 mL/kg, respectively. Starting 3 days after SE, all animals were repeatedly exposed to a battery of motor and behavioral tests, including the bar-holding test, rotarod test, and open field test. RESULTS: In P12 animals, motor impairment occurred 2 months after SE, when significantly worse performance in the rotarod test was found. No difference between controls and experimental rats was found in any other test used. In contrast, P25 animals were significantly poorer in the bar-holding test from postnatal day 34 until adulthood. In open field study, P25 rats were found to be hyperactive during the whole period of testing, whereas P12 animals exhibited an initial period of hypoactivity (in the first test) that was replaced by hyperactivity that lasted until 2 months of age. In the last test performed at the age of 98 days, experimental P12 animals were again less active than age-matched controls. CONCLUSIONS: Animals of both age groups exhibited permanent changes of motor performance; however, both the pattern and the time course of these changes was related to age when SE was elicited.

Behavioral and metabolic changes in immature rats during seizures induced by homocysteic acid: the protective effect of NMDA and non-NMDA receptor antagonists.

Bilateral intracerebroventricular infusion of dl-homocysteic acid (DL-HCA) (600 nmol on each side) to immature 12-day-old rats induced generalized clonic-tonic seizures, recurring frequently for at least 90 min, with a high rate of survival. Electrographic recordings from sensorimotor cortex, hippocampus, and striatum demonstrated isolated spikes in the hippocampus and/or striatum as the first sign of dl-HCA action. Generalization of epileptic activity occurred during generalized clonic-tonic seizures, but electroclinical correlation was very low; dissociation between EEG pattern and motor phenomena was common. Seizures were accompanied by large decreases of cortical glucose and glycogen and by approximately 7- to 10-fold accumulation of lactate. ATP and phosphocreatine (PCr) levels remained unchanged even during longlasting (3 h) convulsions. Metabolite levels became normalized during the recovery period (24 h). The examination of the effect of selected antagonists of NMDA [AP7 (18.5 and 37 mg/kg, respectively), MK-801 (0.5 mg/kg)] and non-NMDA [NBQX (10, 15 and 30 mg/kg, respectively)] receptors revealed that seizures could be attenuated or prevented (depending on the dose employed) by antagonists of both NMDA and non-NMDA receptors, as evaluated not only according to the suppression of behavioral manifestations of seizures, but also in terms of the protection of metabolite changes accompanying seizures. All antagonists employed, when given alone in the same doses as those used for seizure protection, did not influence metabolite levels, with the exception of increased glucose concentrations. Furthermore, the pronounced anticonvulsant effect could be achieved by the combined treatment with low subthreshold doses of NMDA (AP7) and non-NMDA (NBQX) receptor antagonists, which may be of potential significance for a new approach to the treatment of epilepsy.