Expression of nestin in the hippocampal formation of rats submitted to the pilocarpine model of epilepsy

Nestin is an embryonic intermediate filament component protein, transiently expressed by the immediate precursor cells of neurons and glia, during brain development. We studied the nestin distribution in the hippocampal formation of rats submitted to pilocarpine model of epilepsy. Animals were studied during the acute, silent and chronic phases. Rats from control and acute groups presented absence of nestin-immunoreactivity (IR) in the hippocampal cells. In contrast, cells from this region presented strong nestin IR during the silent phase (3 and 7 days after status epilepticus (SE) onset), disappearing 14 days after SE. Nestin IR cells were scattered expressed in all hippocampal formation during the chronic phase. Almost all nestin IR cells exhibited glial fibrillary acidic protein (GFAP), which seems to revert to a more primitive glial form, as part of an adaptive response, transiently re-expressing phenotypic features typical of earlier stages of glial development. The re-expression of this developmental protein in the damaged cerebral tissue suggests that nestin may play an important role in the reconstruction of the glial cytoskeleton and/or remodeling events occurring in the pilocarpine model of epilepsy. Understanding how astrocytes influence network function in the injured hippocampus may, therefore, provide insight into epileptogenic mechanisms.     

Neuropeptide-Y immunoreactivity in the pilocarpine model of temporal lobe epilepsy

 Neuropeptide-Y (NPY) is expressed by granule cells and mossy fibres of the hippocampal dentate gyrus during experimental temporal lobe epilepsy (TLE). This expression may represent an endogenous damping mechanism since NPY has been shown to block seizure-like events following high-frequency stimulation in hippocampal slices. The pilocarpine (PILO) model of epilepsy is characterized by an acute period of status epilepticus followed by spontaneous recurrent seizures and related brain damage. We report peroxidase-antiperoxidase immunostaining for NPY in several brain regions in this model. PILO-injected animals exhibited NPY immunoreactivity in the region of the mossy fibre terminals, in the dentate gyrus inner molecular layer and, in a few cases, within presumed granule cells. NPY immunoreactivity was also dramatically changed in the entorhinal cortex, amygdala and sensorimotor areas. In addition, PILO injected animals exhibited a reduction in the number of NPY-immunoreactive interneurons compared with controls. The results demonstrate that changes in NPY expression, including expression in the granule cells and mossy fibres and the loss of vulnerable NPY neurons, are present in the PILO model of TLE. However, the significance of this changed synthesis of NPY remains to be determined. Received: 19 August 1996 / Accepted: 21 March 1997     

早期安定干预对匹罗卡品诱导颞叶癫痫小鼠学习记忆能力变化的影响

目的:研究早期使用安定麻醉对匹罗卡品(PILO)诱导的颞叶癫痫小鼠的学习记忆能力的变化,从行为学角度评价抑制点燃效应对颞叶癫痫造模程度的影响。方法:腹腔注射PILO建立颞叶癫痫小鼠模型,分PILO癫痫组(A组)、安定麻醉条件下PILO癫痫组(B组)、安定麻醉对照组(C组),正常对照组(D组),对照组腹腔注射与PILO等量的生理盐水。各组小鼠进行Morris水迷宫学习记忆实验,测其寻找到隐藏平台所需潜伏期。结果:Morris水迷宫实验中,A组癫痫小鼠逃避潜伏期时间明显延长(P<0.05),B组癫痫小鼠第一次癫痫发作程度有大幅度的减轻,逃避潜伏期时间延长,但延长时间较正常情况下点燃癫痫小鼠低。结论:早期使用安定麻醉可明显改善颞叶癫闲小鼠学习记忆能力。     

Circadian control of neural excitability in an animal model of temporal lobe epilepsy

We provide experimental evidence for the emerging imbalance in the firing activity of two distinct classes (type 1 and type 2) of population spikes recorded from the hippocampal area CA1 in an animal model of temporal lobe epilepsy. We show that during the latent period of epileptogenesis following status epilepticus inducing brain injury, there is a sustained increase in the firing rate of type 1 population spikes (PS1) with a concurrent decrease in the firing rate of type 2 population spikes (PS2). Both PS1 and PS2 firing rates are observed to follow a circadian rhythm and are in-phase in control rats. Following brain injury there is an abrupt phase shift in the circadian activity of the PS firing rates. We hypothesize that this abrupt phase shift is the underlying cause for the emergence of imbalance in the firing activity of the two PS. We test our hypothesis in the framework of a simple two-dimensional Wilson–Cowan model that describes the interaction between firing activities of populations of excitatory and inhibitory neurons.     

Long-term potentiation of evoked and spontaneous neuronal activity in the grafted hippocampus

Summary Adult rats with unilateral fimbria-fornix lesion received fetal hippocampal grafts into the lesion cavity. Seven to ten months after the transplantation the graft was examined for long-term potentiation (LTP) in response to host hippocampus and direct graft stimulation. High frequency tetanizing trains delivered to either the host hippocampus or the graft resulted in augmented field potentials and prolonged neuronal discharges in the graft lasting several hours. Very low currents (10–30 A) were required to induce LTP by direct graft stimulation. In addition to the enhancement of evoked responses, the frequency of occurrence of spontaneously occurring EEG spikes and concurrent population neuronal bursts in the graft increased significantly after the tetanizing trains. These findings suggest that the physiological-biochemical mechanisms required for plastic changes of synaptic efficacy are present in the grafted hippocampus.     

Behavioral and genetic effects promoted by sleep deprivation in rats submitted to pilocarpine-induced status epilepticus

The interaction between sleep deprivation and epilepsy has been well described in electrophysiological studies, but the mechanisms underlying this association remain unclear. The present study evaluated the effects of sleep deprivation on locomotor activity and genetic damage in the brains of rats treated with saline or pilocarpine-induced status epilepticus (SE). After 50 days of pilocarpine or saline treatment, both groups were assigned randomly to total sleep deprivation (TSD) for 6 h, paradoxical sleep deprivation (PSD) for 24 h, or be kept in their home cages. Locomotor activity was assessed with the open field test followed by resection of brain for quantification of genetic damage by the single cell gel electrophoresis (comet) assay. Status epilepticus induced significant hyperactivity in the open field test and caused genetic damage in the brain. Sleep deprivation procedures (TSD and PSD) did not affect locomotor activity in epileptic or healthy rats, but resulted in significant DNA damage in brain cells. Although PSD had this effect in both vehicle and epileptic groups, TSD caused DNA damage only in epileptic rats. In conclusion, our results revealed that, despite a lack of behavioral effects of sleep deprivation, TSD and PSD induced genetic damage in rats submitted to pilocarpine-induced SE.     

Effects of experimental hypercapnia on hippocampal long-term potentiation in anesthetized rats

The effects of hypercapnia, which has been reported to impair consciousness, on the long-term potentiation of the population spike in the CA1 pyramidal cell of the hippocampus in anesthetized rats were studied. Experimental hypercapnemia was induced by inspired 13% CO₂ with 21% O₂. Arterial blood gas analysis after 80 min inspired 13% CO₂ showed pH 7.08±0.05, PCO₂=104.09±12.86 mmHg, PO₂=90.71±18.89 mmHg, BE −4.64±2.97 (mean±SD, n=18). Inspired 13% CO₂ reduced the amplitude of the population spike to 50% of the baseline. After delivery of tetanic stimulation (400 Hz, five bursts of eight pulses, inter-burst interval 1 s) population spike height was enhanced to pre-tetanic levels. Withdrawal of inspired CO₂ unmasked an increase in population spike amplitude. These findings suggest that acute retention of carbon dioxide, which is designated as pure hypercapnemia without hypoxemia, may suppress hippocampal synaptic transmission but not its plasticity.     

Membrane properties,response to amines and to tetanic stimulation of hippocampal neurons in the genetically epileptic mutant mouse tottering

Summary The petit-mal seizures of the tottering mutant mouse (tg) have been attributed to an exaggerated noradrenergic projection from locus coeruleus to the telencephalon (Noebels 1984). In order to investigate the possible epileptogenic mechanisms involved, we have compared hippocampal slices from epileptic (tg/tg) and phenotypically healthy (tg/+) mice. Resting potentials, action potentials and afterpotentials, membrane impedances and time constants were not significantly different in 11 neurons from each group. Bath application of noradrenaline, isoproterenol and histamine or a transient exposure to Mg⁺⁺-free medium caused a long lasting increase in extracellularly recorded population spikes induced in CA1 by electrical stimulation of stratum radiatum. Isoproterenol blocked the calcium dependent afterhyperpolarization and accommodation of firing. Tetanization of afferent fibres evoked post-tetanic potentiation and long-term potentiation. All these results are qualitatively similar to those previously described in rats and guinea pigs and have revealed no significant difference between tg/tg and tg/+ mice.     

Investigation of oxidative stress involvement in hippocampus in epilepsy model induced by pilocarpine

The relationship between free radical and scavenger enzymes has been found in the epileptic phenomena and reactive oxygen species have been implicated in seizure-induced neurodegeneration. Using the epilepsy model obtained by systemic administration of pilocarpine in rats, we investigated the lipid peroxidation, nitrite content, superoxide dismutase (SOD) and catalase activities in the hippocampus of rats during chronic period. The enzyme activities as well as the lipid peroxidation and nitrite concentrations were measured using spectrophotometric methods and the results compared to values obtained from saline-treated animals. The superoxide dismutase and catalase activities increased during the chronic phase. In addition, lipid peroxidation and nitrite levels increased in same period in the hippocampus of animals observed during spontaneous recurrent seizures. Previous studies showed that animals presenting seizures and submitted to 24 h of status epilepticus showed normal levels of superoxide dismutase and increased in catalase activities as well as an increase in hippocampal lipid peroxidation and nitrite concentrations. These results show a direct evidence of lipid peroxidation and nitrite during seizure activity that could be responsible for neuronal damage in the hippocampus of rats, during the establishment of pilocarpine model of epilepsy.     

Efficacy of fish liver oil and propolis as neuroprotective agents in pilocarpine epileptic rats treated with valproate

Objective: To evaluate the action of fish liver oil and propolis in pilocarpine epileptic rats treated with the anticonvulsant drug valproate. Methods: Seven groups of rats were treated daily for six months: control; fish liver oil (0.4 ml/kg b.w); propolis (50 mg/kg b.w); pilocarpine-treated rats (epileptic control); epileptic rats treated with valproate (400 mg/kg b.w); groups 6 and 7, epileptic rats treated with valproate plus fish liver oil or propolis. Results: Pilocarpine administration caused a significant increase in hippocampal dopamine and serotonin levels accompanied with a significant decrease in their levels in serum. Lipid peroxidation level and LDH activity in hippocampus were significantly increased after pilocarpine treatment whereas Na⁺/K⁺-ATPase activity and total antioxidant capacity were significantly decreased compared to the controls. Animals treated with the combined treatments showed a significant improvement in tested parameters towards the normal values of the control. Conclusion: Fish liver oil and propolis when given in combination with valproate, neuroprotected against the neurophysiological disorders induced by pilocarpine epilepsy in rats.     

Effects of ventral hippocampal long-term potentiation and depression on the gamma-band local field potential in anesthetized rats

We examined the effect of long-term potentiation or depression (LTP or LTD) on the local field potential, focusing on the gamma-band (40–100 Hz) power, in the ventral hippocampus CA1 of anesthetized rats. LTP and LTD induction in the CA3–CA1 pathway increased the CA1 spontaneous gamma-band power by around 40 and 80–100 Hz, respectively, while neither changed the evoked levels significantly. These results suggest that the ventral CA1 local field potential can maintain bidirectional plasticity in the steady state for the long term. Given the involvement of synaptic plasticity in learning and memory, the gamma-band power change associated with LTP/LTD may relate to ventral hippocampal functions. The LTP increased the spontaneous power at around 40 Hz of the gamma-band frequency in the ventral CA1, and the LTD did the same at 80–100 Hz. The biphasic increase may distribute the subsequent input appropriately to regulate the relevant synaptic history in the ventral CA1 and anatomically related structures in vivo.     

Cardiovascular adaptive responses in rats submitted to moderate resistance training

The present study investigated the effects of 8 week of resistance training (RT) on hemodynamic and ventricular function on cardiac myosin ATPase activity, and on contractility of papillary muscles of rats. Groups: control (CO), electrically stimulated (ES), trained at 60% (TR 60%) and 75% of one repetition maximum (1RM) (TR 75%). Exercise protocol: 5 sets of 12 repetitions at 60 and 75% of 1RM, 5 times per week. The CO and ES groups had similar values for parameters analyzed (P > 0.05). Blood pressure (BP), heart rate (13%), left ventricle systolic pressure (LVSP 13%) decreased and cardiac myosin ATPase activity increased in the TR 75% group (90%, P < 0.05). The contractile performance of papillary muscles increased in trained rats (P < 0.05). Eight weeks of RT was associated with lowering of resting BP, heart rate and LVSP, improvements in contractility of the papillary muscle and an increase of cardiac myosin ATPase activity in rats.     

Reactive oxygen species generated by NADPH oxidase are involved in neurodegeneration in the pilocarpine model of temporal lobe epilepsy

Reactive oxygen species (ROS) appear to be involved in several neurodegenerative disorders. We tested the hypothesis that oxidative stress could have a role in the hippocampal neurodegeneration observed in temporal lobe epilepsy induced by pilocarpine. We first determined the spatio-temporal pattern of ROS generation, by means of detection with dihydroethidium oxidation, in the CA1 and CA3 areas and the dentate gyrus of the dorsal hippocampus during status epilepticus induced by pilocarpine. Fluoro-Jade B assays were also performed to detect degenerating neurons. ROS generation was increased in CA1, CA3 and the dentate gyrus after pilocarpine-induced seizures, which was accompanied by marked cell death. Treatment of rats with a NADPH oxidase inhibitor (apocynin) for 7 days prior to induction of status epilepticus was effective in decreasing both ROS production (by an average of 20%) and neurodegeneration (by an average of 61%). These results suggest an involvement of ROS generated by NADPH oxidase in neuronal death in the pilocarpine model of epilepsy.     

The potassium channel modulator flupirtine shifts the frequency-response function of hippocampal synapses to favour LTD in mice

Flupirtine is a centrally acting nonopioid analgesic with muscle-relaxant properties. Flupirtine has been found to activate inwardly rectifying potassium conductances and hence to indirectly inhibit the activation of NMDA receptors. NMDA receptor activation is crucial for the induction of long-term potentiation (LTP) of synaptic transmission, which is considered as cellular correlate of learning and memory and of central sensitization in chronic pain states. Although flupirtine has been widely used for the management of pain, its effects on synaptic plasticity have not yet been investigated. We, therefore, performed extracellular and whole-cell patch-clamp recordings in hippocampal slices of mice to examine the effects of flupirtine on synaptic plasticity and neuronal membrane properties. Excitatory postsynaptic potentials (EPSPs) in the CA1 region were evoked alternately by stimulating two independent Schaffer collateral-commissural inputs. LTP and long-term depression (LTD) were induced by different stimulation paradigms (100 Hz, 10 Hz, 5 Hz, and 1 Hz). Flupirtine (30 μM) diminished the degree of LTP and enhanced LTD. This effect is most likely due to the hyperpolarization of CA1 pyramidal neurons and the reduction of their input resistance found after application of flupirtine. The observed effects on synaptic strength could underly the beneficial effects of flupirtine on different types of chronic pain.     

Physical conditioning in rats influences the central and peripheral catecholamine responses to sustained exercise

We have investigated the effect of treadmill running in rats (25m · min^–1 using a 3 % gradient; for 1 h or 2 h) on the cortical extracellular concentrations of noradrenaline (NA) and its main metabolites — 3,4-dihydroxyphenylglycol and 3-methoxy-4-hydroxyphenylglycol-and the plasma adrenaline (A) and NA concentrations in relation to prior physical conditioning (1 or 2-h running -day-¹ for 12 days). Cortical microdialysates and peripheral blood were collected during 1-h resting, 1-h or 2-h running and for 1 h after exercise. Catecholamines and their metabolites were quantitated using high performance liquid chromatography with electrochemical detection. Treadmill running stimulated concomitantly peripheral catecholamine secretion and central noradrenergic activity, i.e. NA turnover and release. The effect extended into the recovery period even more as the duration of the run increased. Prior physical conditioning greatly influenced the central and peripheral catecholamine responses: the 1-h trained rats experienced the 2-h run as a stressful new event eliciting great long-lasting catecholamine responses, whereas the 2-h trained rats exhibited a progressive sustained catecholamine increase with an earlier onset of the central NA release. The data are discussed in relation to the psychological and intellectual effects of exercise and physical fitness in humans. In addition, the positive correlation found between the central noradrenergic activation and peripheral A secretion confirmed and extended our previous observations in exercising men and gave support to the hypothesis that the elevation of circulating A can be a relevant factor mediating — directly or indirectly — the exercise-induced central effects.     

Effect of maternal weight during pregnancy on offspring muscle strength response to resistance training in late adulthood

Purpose

Maternal obesity can unfavorably influence offspring body composition, muscle strength, and possibly muscle’s adaptability to training, but the human studies are scarce. Therefore, we aimed to investigate the effect of maternal obesity on offspring muscle strength responses to resistance training intervention in elderly frail women.

Age-dependent mortality in the pilocarpine model of status epilepticus

Status epilepticus (SE) is an acute neurological emergency associated with significant morbidity and mortality. Age has been shown to be a critical factor in determining outcome after SE. Understanding the causes of this increased mortality with aging by developing an animal model to study this condition would play a major role in studying mechanisms to limit the mortality due to SE. Here we employed pilocarpine to induce SE in rats aged between 5 and 28 weeks. Similar to clinical studies in man, we observed that age was a significant predictor of mortality following SE. While no deaths were observed in 5-week-old animals, mortality due to SE increased progressively with age and reached 90% in 28-week-old animals. There was no correlation between the age of animals and severity of SE. With increasing age mortality occurred earlier after the onset of SE. These results indicate that pilocarpine-induced SE in the rat provides a useful model to study age-dependent SE-induced mortality and indicates the importance of using animal models to elucidate the mechanisms contributing to SE-induced mortality and the development of novel therapeutic interventions to prevent SE-induced death.     

Interstrain differences of ionotropic glutamate receptor subunits in the hippocampus and induction of hippocampal sclerosis with pilocarpine in mice

Rodent strains used in epilepsy research have various neurological characteristics. These differences were suggested to be attributed to the diverse densities of the ionotropic glutamate receptor (iGluR) subunits. However, previous studies failed to find interstrain differences in the hippocampal receptor levels.We supposed that a detailed layer-to-layer analysis of the iGluR subunits in the hippocampus might reveal strain-dependent differences in their base lines and reactions induced by pilocarpine (PILO) between two mouse strains without documented ancestors.Levels of iGluR subunits in Balb/c and NMRI mice were compared using semiquantitative immunohistochemistry. The alterations in the neuronal circuitry were validated by neuropeptide Y (NPY) and neuronal nuclear antigen (NeuN) immunostainings.Immunohistochemistry showed interstrain laminar differences in some subunits of both the control and PILO-treated animals. The seizure-induced irreversible neuronal changes were accompanied by reduced GluA1 and GluA2 levels. Their changes were inversely correlated in the individual NMRI mice by Pearson's method. Increase in NPY immunoreactivity showed positive correlation with GluA1, and negative correlation with GluA2. The NMRI strain was susceptible to PILO-induced hippocampal sclerosis, while the Balb/c animals showed resistance.Basal levels of iGluRs differ in mouse strains, which may account for the interstrain differences in their reactions to the convulsant.     

Kindling in the early postnatal period: Effects on the dynamics of age-related changes in electrophysiological characteristics of hippocampal neurons

The effects of chronic administration of pentylenetetrazole (PTZ) during early ontogenesis (from postnatal day 14) on the dynamics of age-related changes in electrophysiological characteristics of rat hippocampal slices were studied. Unlike the situation in adult animals, convulsive activity did not develop in rat pups in response to repeated injections. Comparison of the amplitude characteristics of total monosynaptic responses of neurons in hippocampal field CA1 to application of single and paired (separated by 70 msec) stimulation of Schäffer collaterals during the period of maximally intense hippocampal synaptogenesis (at weeks 2–3 of postnatal development) revealed no significant differences between the control group (administration of isotonic saline) and the group given PTZ. The level of suppression of facilitation in paired-pulse stimulation with a short interstimulus interval (15 msec) was significantly less in hippocampal slices from rat pups from the PTZ group. However, as compared with the passive control, the direction of rearrangements in the two experimental group was essentially the same. Nonetheless, regular administration of PTZ during the period of maximally intense hippocampal maturation affected the development of its characteristics. This was not only apparent as a deficiency of inhibitory processes. Increases in the intensity of test stimuli applied to hippocampal slices from PTZ-treated rat pups at 27–48 days of age led to relatively lower response amplitudes as compared with those seen in hippocampal slices from control (given isotonic saline) rats of the same age. The level of facilitation in paired-pulse stimulation with an interstimulus interval of 70 msec showed no difference, decreasing to similar extents in both groups as compared with the passive control group. In addition, hippocampal slices from the PTZ group showed significant decreases in the magnitude of long-term potentiation. Changes occurring in the hippocampus after regular administration of PTZ did not correlate with the development of convulsive activity. The only significant relationship involving the intensity of convulsions was with the increase (compared with the normal for age) in the amplitudes of responses to minimal-intensity test stimuli.     

不同强度有氧运动周期训练疲劳模型大鼠心肌形态变化及超量恢复规律

BACKGROUND: “Over-recovery theory” is the basic theory of sports training, but study about the visceral over-recovery is few, let alone about heart after aerobic exercise. OBJECTIVE:To observe the morphological changes of myocardial tissue in rats after different cycles of aerobic exercise, and the recovery pattern of heart function within 72 hours. METHODS:132 Sprague-Dawley rats were randomly divided into groups of control (n=6), single-cycle (low-intensity exercise, n=42), double-cycle (moderate-intensity exercise, n=42), and triple-circle (high-intensity exercise, n=42). Rats in the latter three groups underwent 1-week adaptive swimming in accordance with the way of increasing load (from 3% to 6%), followed by aerobic exercise of swimming according to their corresponding training cycle. Subsequently, samples were collected to detect the levels of creatine kinase, superoxide dismutase, succinic dehydrogenase and glutamic-oxaloacetic transaminase in myocardial tissue; left cardiac apex tissues after embedded section were observed by hematoxylin-eosin staining. RESULTS AND CONCLUSION: (1) Compared with the control group, the morphological changes of myocardial tissue immediately after exercise became more obvious with the increasing intensity. (2) Compared with the control group, significantly increased levels of superoxide dismutase, succinic dehydrogenase and glutamic-oxaloacetic transaminase conld be found in the single-cycle group (P < 0.05), and showed over-recovery at 12-36 hours after exercise; all indicators were significantly increased in the double-cycle group showing over-recovery at 24-48 hours (P < 0.05); while in the triple-circle group, succinic dehydrogenase exhibited over-recovery only (P < 0.05), and each indicator level was low probably indicating over fatigue. (3) These findings suggest that compared with the triple-cycle high- intensity training, single-cycle and double-cycle training will be better, and it is advisable to undergo double-cycle aerobic exercise in practice. 中国组织工程研究杂志出版内容重点：肾移植;肝移植;移植;心脏移植;组织移植;皮肤移植;皮瓣移植;血管移植;器官移植;组织工程