Pentylenetetrazol-induced recurrent seizures in rat pups: time course on spatial learning and long-term effects

PURPOSE: Recurrent seizures in infants are associated with a high incidence of neurocognitive deficits. Animal models have suggested that the immature brain is less vulnerable to seizure-induced injury than is that in adult animals. We studied the effects of recurrent neonatal seizures on cognitive tasks performed when the animals were in adolescence and adulthood. METHODS: Seizures were induced by intraperitoneal injection of pentylenetetrazol (PTZ) for 5 consecutive days, starting from postnatal day 10 (P10). At P35 and P60, rats were tested for spatial memory by using the Morris water maze task. In adulthood, motor performance was examined by the Rotarod test, and activity level was assessed by the open field test. Seizure threshold was examined by inhalant flurothyl. To assess presence or absence of spontaneous seizures, rats were video recorded for 4 h/day for 10 consecutive days for the detection of spontaneous seizures. Finally, brains were examined for histologic evidence of injury with cresyl violet stain and Timm staining in the supragranular zone and CA3 pyramidal cell layers of the hippocampus. RESULTS: PTZ-treated rats showed significant spatial deficits in the Morris water maze at both P35 and P60. There were no differences in seizure threshold, motor balance, or activity level during the open field test. Spontaneous seizures were not recorded in any rat. The cresyl violet stain showed no cell loss in either the control or experimental rats. PTZ-treated rats exhibited more Timm staining in the CA3 subfield. However, the control and experimental rats showed similar Timm staining within the supragranular zone. CONCLUSIONS: Our findings indicate that recurrent PTZ-induced seizures result in long-term cognitive deficits and morphologic changes in the developing brain. Furthermore, these cognitive deficits could be detected during pubescence.     

Pentylenetetrazol-Induced Seizures Decrease γ-Aminobutyric Acid-Mediated Recurrent Inhibition and Enhance Adenosine-Mediated Depression

Summary: To elucidate the consequences of convulsions, we examined biochemically and electrophysiologically the brains of mice that had sustained two complete tonicclonic convulsions after administration of pentylenetetrazol (PTZ 50 mg/kg intraperitoneally, i.p.), 48 and 24 h before decapitation. Control mice were injected with saline. Input/output curves of the extracellular synaptic responses in the CAI area of hippocampal slices showed that PTZ-induced seizures do not establish the persistent change in hippocampal excitability itself that can be detected in vitro. However, use of the paired-pulse stimulation paradigm showed that γ-aminobutyric acid, (GABA)-mediated recurrent inhibition was significantly weaker (by 19–25%) in the CA1 area of slices from PTZtreated mice (PTZ slices) as compared with slices from control mice (control slices). The density of GABA, receptors (high-affinity component) was also lower in hippocampus (by 19%) and cortex (by 14%) of PTZ-treated mice. A GABA-related disinhibitory mechanism underlying PTZ seizures may thus persist for 1 day after the seizure, predisposing the brain to subsequent seizures. On the other hand, the depressant effect of a single dose of adenosine 10 μ M on the CA1 synaptic response was stronger (by 35% on population spikes) and longer lasting in PTZ slices as compared with controls. This could be attributed to significantly higher adenosine A₁ receptor density in hippocampus ( B _max of [³H]CHA was higher by 34%) as well as cortex and cerebellum of these animals. The phenomenon may reflect an adenosine A₁-mediated adaptive mechanism that offers protection from subsequent seizures.     

Effect of neonatal isolation on outcome following neonatal seizures in rats--the role of corticosterone

Emerging evidence indicates that early maternal care permanently modifies the activity of hypothalamic-pituitary-adrenal (HPA) axis and is a critical factor in determining the capacity of the brain to compensate for later encountered insults. The purpose of this study was to determine the role of corticosterone (CORT) in the detrimental effects of neonatal isolation (NI) on seizures. Rats were assigned randomly to the following five groups: (1) control (CONT) rats; (2) NI rats that underwent daily separation from their dams from postnatal day 2 (P2) to P9; (3) status epilepticus (SE) rats, induced by lithium-pilocarpine (Li-Pilo) model at P10; (4) NI plus SE (NIS) rats and (5) NISM rats, a subset of NIS rats receiving metyrapone (100 mg/kg), a CORT synthesis inhibitor, immediately after SE induction. At P10, plasma CORT levels were compared at baseline in CONT and NI rats and in response to Li-Pilo-induced SE among SE, NIS and NISM rats. We evaluated the spatial memory in the Morris water maze at P50 approximately 55, the expression of hippocampal cyclic adenosine monophosphate (cAMP)-responsive element-binding protein phosphorylation at serine-133 (pCREBSer-133) at P55, hippocampal neuronal damage at P80 and seizure threshold at P100. The isolated rats exhibited higher CORT release in response to SE than non-isolated rats, and the NIS rats had greater cognitive deficits and decreased seizure threshold compared to the CONT, NI and SE groups. By contrast, the NISM group, compared to the NIS group, showed a normal CORT response to SE and better spatial memory but no difference in seizure threshold. Compared to the CONT group, the hippocampal pCREBSer-133 level was significantly reduced in all experimental groups (NI, SE, NIS, NISM) with no differences between groups. All rats were free of spontaneous seizures later in life and had no discernible neuronal loss in the hippocampus. Results in this model demonstrate repetitive NI enhances response of plasma CORT to SE, and exacerbates the neurological consequences of neonatal SE. Amelioration of neurological sequelae following reduction of the SE-induced excessive rise in plasma CORT implicates CORT in the pathogenesis of NI increasing the vulnerability to seizures.     

Menhaden fish oil improves spatial memory in rat pups following recurrent pentylenetetrazole-induced seizures

This study investigated the effects of two supplementary dietary oils (fish oil and corn oil) as parts of isocaloric/isoproteic diets on growth, brain fatty acid composition, and behavior in rat pups with recurrent seizures. Recurrent seizures were induced by injecting rat pups with pentylenetetrazole (PTZ) between P10 (10 days of age) and P14. Either menhaden fish oil (FO) or corn oil (CO) was given as supplemental dietary oil throughout the experiment from P3 to P40. We assessed the effects of the two supplemental dietary oils on spatial memory, histomorphology, and fatty acid composition of brain tissue at the end of the study on P40. Rats that received dietary FO performed significantly better in the Morris water maze, a test used to examine spatial performance in rats; the FO group had significantly shorter escape latencies (P=0.041) during the escape test. Compared with the CO group, the FO group stayed a longer time (P=0.015) and swam a longer distance (P=0.033) in the target quadrant in the spatial probe test. The FO group had significantly higher brain docosahexaenoic acid (P0.01) and significantly lower brain C20:3 n-6 and C20:4 n-6 (P<0.01 and P=0.031) levels compared with the CO group, but the two groups did not differ significantly with respect to neuronal cell loss in the histomorphology study. This study demonstrated that, compared with CO, FO is better in improving spatial memory in rats following recurrent PTZ-induced seizures.     

Pentylenetetrazol-induced seizures in immature rats provoke long-term changes in adult hippocampal cholinergic excitability

PURPOSE: We previously demonstrated that the anticholinesterase eserine provokes interictal-like discharges in the CA3 area of hippocampal slices from rats in which generalized seizures had been induced by pentylenetetrazol (PTZ) when immature. In this study, we investigated several factors as the possible mechanism for this effect, including age at convulsions. METHODS: Rats were injected with PTZ on postnatal day (P) 18-20 or >P60, and neuronal activity was recorded intra- and extracellularly from CA3 5-10 or >40 days later. In additional experiments, convulsions were triggered by kainate or were blocked by pentobarbital. Hippocampal (a) acetylcholine (ACh) innervation density was measured by immunocytochemistry, and ACh and gamma-aminobutyric acid (GABA) contents were determined by high-performance liquid chromatography (HPLC)-electrospray ionization. RESULTS: The excitatory effect of eserine was the most consistent in slices from rats PTZ-treated when immature and after the long interval, whereas the reverse was true in rats treated as adults. This effect was dependent on the occurrence of a seizure and was less prevalent when the seizure had been provoked by kainate. Adult animals PTZ-treated at P20 did not differ from control in (a) poly- or monosynaptic GABAA and GABAB CA3 inhibitory postsynaptic potentials (IPSPs); (b) density of ACh innervation; or (c) tissue content of ACh and GABA. CONCLUSIONS: A PTZ-induced generalized seizure in immature rat provokes endogenous ACh-induced interictal-like discharges in adult hippocampal CA3. This effect is only transiently observed if the seizure was induced in adult. It does not appear to be related to a change in GABAergic inhibition, in density of ACh innervation, or in ACh or GABA content.     

Consequences of neonatal seizures in the rat: Morphological and behavioral effects

Whereas neonatal seizures are a predictor of adverse neurological outcome, there is controversy regarding whether seizures simply reflect an underlying brain injury or can cause damage. We subjected neonatal rats to a series of 25 brief flurothyl-induced seizures. Once mature the rats were compared with control littermates for spatial learning and activity level. Short-term effects of recurrent seizures on hippocampal excitation were assessed by using the intact hippocampus formal preparation and long-term effects by assessing seizure threshold. Brains were analysed for neuronal loss, sprouting of granule cell axons (mossy fibers), and neurogenesis. Compared with controls, rats subjected to neonatal seizures had impaired learning and decreased activity levels. There were no differences in paired-pulse excitation or inhibition or duration of afterdischarges in the intact hippocampal preparation. However, when studied as adults, rats with recurrent flurothyl seizures had a significantly lower seizure threshold to pentylenetrazol than controls. Rats with recurrent seizures had greater numbers of dentate granule cells and more newly formed granule cells than the controls. Rats with recurrent seizures also had sprouting of mossy fibers in CA3 and the supragranular region. Recurrent brief seizures during the neonatal period have long-term detrimental effects on behavior, seizure susceptibility, and brain development.     

An experimental model of generalized seizures for the measurement of local cerebral glucose utilization in the immature rat. II. Mapping of brain metabolism using the quantitative [14C]2-deoxyglucose technique.

The quantitative autoradiographic [14C]2-deoxyglucose technique (2DG) was applied to measure the effects of pentylenetetrazol (PTZ)-induced status epilepticus (SE) on local cerebral metabolic rates for glucose (LCMRglc) in 10 (P10)-, 14 (P14)-, 17 (P17)- and 21 (P21)-day-old rats. To produce long-lasting SE (55 min), the animals received repetitive, timed intraperitoneal injections of subconvulsive doses of PTZ until SE was reached. At P10 and P14, SE induced a marked increase in LCMRglc which affected 66 of the 76 structures studied. Increases were especially high (200-400%) in limbic and motor cortices at P10 and in some brainstem areas at these 2 ages. At P17 and P21, average brain glucose utilization was similar in seizing and control rats, but in PTZ-treated rats reflected a redistribution in local metabolic rates with increases in brainstem, midbrain, hypothalamus and septum, decreases in cortex, hippocampus, some sensory areas and white matter and no change in many motor and limbic structures. In a few cerebral regions, such as hippocampus, dentate gyrus and mammillary body, LCMRglc did not increase at P10 and P14 and decreased at P17 and P21 in PTZ- vs. saline-treated rats. The results of the present study show that the immature brain responds to sustained seizure activity in a specific way according to its maturational state. Moreover, these data allow the mapping of the vulnerability of cerebral structures to seizures, according to their metabolic response to convulsions.     

养血清脑颗粒和丙戊酸联用对戊四氮点燃癫痫大鼠的影响

目的 探讨养血清脑颗粒(YXQNG)联用丙戊酸(VPA)对戊四氮(PTZ)慢性点燃模型大鼠癫痫发作、EEG、认知功能及颞叶、海马T型Ca2+通道蛋白(Cav3.2)表达的影响. 方法 成年雄性SD大鼠40只按随机数字表法分为PTZ组、VPA组、VPA+YXQNG组、NS组,每组10只.前3组大鼠腹腔注射PTZ溶液制作慢性点燃模型,VPA组大鼠在注射PTZ前1 h给予VPA灌胃;VPA+YXQNG组除给予VPA外,注射PTZ前1.5 h给予YXQNG灌胃;NS组腹腔注射生理盐水,每天一次.8周后观察各组大鼠的行为学变化、Y型电迷宫检查大鼠的正确反应率、捕记EEG并应用免疫组化染色检测颞叶和海马Cav3.2的表达. 结果 给药8周后PTZ组大鼠全部达到完全点燃(连续3 d出现Ⅳ级发作或达到Ⅴ级发作),VPA组和VPA+YXQNG组大鼠仅出现0～Ⅱ级发作;Y型电迷宫检查结果显示VPA+YXQNG组大鼠正确反应率高于PTZ组,差异有统计学意义(P＜0.05);EEG结果显示PTZ组大鼠癫痫发作时EEG有明显异常放电,总功率高于用药前,差异有统计学意义(P＜0.05).VPA组、VPA+YXQNG组大鼠用药前后EEG总功率的差值均高于PTZ组,差异有统计学意义(P＜0.05);免疫组化染色结果显示VPA组、VPA+YXQNG组大鼠颞叶和海马Cav3.2表达低于PTZ组,VPA+YXQNG组大鼠颞叶和海马Cav3.2表达低于VPA组,差异均有统计学意义(P＜0.05). 结论 YXQNG和VPA联用能降低癫痫大鼠发作级别、改善认知功能、减少脑部异常放电并降低脑组织Cav3.2水平,有抗癫痫和脑保护作用.

Abstract：

Objective To explore the effet of Yangxue Qingnao granule (YXQNG) on seizures and cognition function of pentylenetetrazole (PTZ)-kindled chronic epileptic rats models, expression of Cav3.2 in the hippocampus and the temporal lobe of these rats, and EEG features of the rats. Methods Forty healthy adult male SD rats were equally divided into 4 groups at random: PTZ group, VPA treatment group, VPA+YXQNG treatment group, normal saline (NS)-control group (n=10). PTZ solution was intraperitoneally injected for 8 weeks to induce the kindling model in the above 3 groups except the NS-control group. VPA by intragastric administration was given to the rats in the VPA treatment group 1 h before PTZ injection; YXQNG and VPA by intragastric administration were given to the rats in the VPA+YXQNG treatment group 1.5 h before PTZ injection. Behavioral changes of the rats were observed 8 weeks after PTZ injection; accuracy rate of response of the rats were examined by electric maze test;EEG was performed; and the expression ofT-type Ca2+ channel protein (Cav3.2) in the temporal lobe and hippocampus was detected by immunohistochemical staining. Results Rats in the PTZ group appeared grade Ⅳ or Ⅴ seizures for 3 consecutive d, and rats in the VPA treatment group, VPA+YXQNG treatment group appeared grade 0-Ⅱ seizures. The accuracy rate of response of the rats in the VPA+YXQNG treatment group was significantly higher than that in the PTZ group (P＜0.05). EEG indicated that paradoxical discharge was noted in rats of PTZ group when seizures appeared, and the total power at the time was obviously higher than that before PTZ injection (P＜0.05). The D-value of total power of EEG in rats of the VPA treatment group and VPA+YXQNG treatment group before and after treatment was significantly higher than that in the PTZ group (P＜0.05). And the level of Cav3.2 in the temporal and hippocampus in rats of the VPA treatment group and VPA+YXQNG treatment group was significantly lower than that in the PTZ group (P＜0.05); as compared with that in the VPA treatment group, the expression of Cav3.2 in the temporal and hippocampus in rats of the VPA+YXQNG treatment group was significantly reduced (P＜0.05). Conclusion The combination use of YXQNG and VPA can decrease the seizure stage, the paradoxical discharge of the brain and the level of Cav3.2 in brain tissue,and improve the cognitive function of the PTZ-kindled rats, indicating that using VAP and YXQNG simultaneously can treat epileptic seizure and protect the neurons.     

Effects of pentylenetetrazole-induced status epilepticus on behavior, emotional memory and learning in immature rats

Status epilepticus (SE) can be harmful to the developing brain. Our knowledge of the emotional and behavioral consequences of generalized SE in developing animals remains limited. Therefore, we investigated the short- and long-term effects of pentylenetetrazole (PTZ)-induced SE on emotional memory and learning and behavioral parameters in immature rats. SE was induced in 16- to 20-day-old rats (P16-P20) using intraperitoneal injections of PTZ (n=21); control rats received saline (n=10). All animals were tested using an elevated T-maze and open-field test 2, 14, 30, and 180 days after SE, to evaluate emotional memory and learning and behavior. Anxiety levels decreased 2 and 14 days after SE, and conditioned learning of PTZ-treated immature rats was better than that of the control rats. These results indicate that a decreased anxiety level facilitates conditioned learning. Behavioral changes are transient, and no emotional memory or learning deficits occur following PTZ-induced SE in immature rats.     

生酮饮食对幼鼠戊四氮诱导痫性发作的影响及海马CA3区形态学观察

目的　探讨生酮饮食 (KD)对幼鼠戊四氮 (PTZ)诱导痫性发作阈值的影响及海马结构的病理改变。方法　通过尾静脉输注 PTZ,测定 KD饲料和普通饲料喂养两组 Wistar幼鼠的痫性发作阈值 ,并对其抽搐行为进行评分 ,同时对致痫后两组幼鼠海马 CA3区的病理学改变进行观察。结果　KD组幼鼠 PTZ诱导的痫性发作阈值明显高于对照组 (P <0 .0 1 ) ,但两组痫性发作的强度差异无显著性 (P >0 .0 5 )。 KD组幼鼠海马 CA3区正常锥体细胞计数较对照组明显增多 ,神经元损伤程度较轻。结论　KD可提高幼鼠 PTZ诱导的痫性发作阈值 ,但不影响发作强度 ;KD可减少痫性发作次数 ,对致痫幼鼠具有神经保护作用。     

戊四氮点燃过程中大鼠海马胶质细胞增生和突触重建的研究

目的探讨戊四氮点燃过程中海马胶质细胞增生及突触重建与慢性癫痫发病机制的关系。方法大鼠随机分为对照组、非药物干预组(戊四氮35mg/kg,腹腔注射,每日一次)和药物干预组(苯巴比妥30mg/kg,戊四氮35mg/kg,均为腹腔注射,每日一次)。采用免疫组织化学方法观察胶质原纤维酸性蛋白(GFAP)和神经细胞粘附分子(NCAM)表达水平。结果非药物干预组大鼠注射戊四氮后在行为学未出现惊厥,脑电图未出现痫性放电的点燃前潜伏期内,出现突触重建和胶质细胞增生,以海马CA3区、门区明显,与对照组比较,有显著性差异(P<0.05);与药物干预组对应时间点比较,亦有显著性差异(P<0.05)。结论大鼠注射戊四氮后引起反应性胶质细胞增生和神经元可塑性改变,可能与形成异常神经元放电环路,最终诱发癫痫发作有关,苯巴比妥可抑制异常神经网络的建立,预防癫痫发生。     

Investigation of the effects of tianeptine and fluoxetine on pentylenetetrazole-induced seizures in rats

The effects of tianeptine and fluoxetine on pentylenetetrazole (PTZ)-induced seizures in rats were investigated. Female Wistar rats (172-278 g) were used in the study. Tianeptine (1.25, 2.5, 5, 10 and 20 mg/kg) and fluoxetine (2.5, 5, 10 and 20 mg/kg) or saline were injected to rats intraperitoneally 30 min before PTZ (50 mg/kg) injections. Immediately after PTZ administrations, latency and intensity of the PTZ-induced seizures was recorded and scored, respectively. Fluoxetine (2.5-20 mg/kg) did not produce any significant difference in latency and intensity of the PTZ-induced seizures. Although tianeptine (1.25-20 mg/kg) also did not affect the latency time, it produced significant attenuations in the intensity of the seizures. Tianeptine did not cause any significant change in the locomotor activity of the rats. The results of this preliminary study suggest that tianeptine but not fluoxetine has some inhibitory effects on PTZ-induced seizures in rats.     

Effects of intrahippocampal injection of ghrelin on spatial memory in PTZ-induced seizures in male rats

Ghrelin (gh) is a peptide hormone that may affect learning and memory. There is some evidence that ghrelin can have antiepileptic effects. So we decided to investigate the possible effects of ghrelin on spatial memory following PTZ-induced seizures in male rats. Ninety male rats were divided into 9 groups including control, saline, ghrelin (0.3, 1.5 or 3 nmol) and pentylenetetrazol (PTZ, 50 mg/kg, i.p.) plus saline or ghrelin (0.3, 1.5 or 3 nmol). All groups were trained in Morris water maze (MWM) for two consecutive days. Our results showed that ghrelin significantly improves spatial memory at the doses of 1.5 or 3 nmol (P < 0.05) in normal rats. We also demonstrated the significant impairment of spatial memory in PTZ group (P < 0.05). Intrahippocampal injection of ghrelin at the dose of 3 nmol significantly improved spatial memory in PTZ + gh group compared to PTZ group (P < 0.05). These findings suggest that ghrelin as a neuropeptide can improve spatial memory in PTZ-treated rats.     

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.     

一氧化氮合酶抑制剂对戊四氮诱导大鼠点燃模型及该酶阳性神经元的影响

目的：探讨一氧化氮（ＮＯ）在癫癎 发病中的作用．方法：ｉｐ ４０ｍｇ·ｋｇ－１·ｄ－１戊四氮 ３０ｍｉｎ前注射 ２５ｍｇ·ｋｇ－１的 ＮＧ－硝基－左旋－精氨酸（Ｌ－ＮＮＡ）,连续 ２２ｄ,观察两组的行为改变及点燃串,同时对 ３组动物海马,大脑皮质一氧化氮合酶（ＮＯＳ）阳性神经元的变化输入图像扫描仪,对其胞体平均灰度值进行比较。结果：Ｌ－ＮＮＡ可明显抑制戊四氮点燃模型;戊四氮点燃大鼠模型海马,大脑皮质神经元的ＮＯＳ活性显著增高．结论：ＮＯ参与了戊四氮点燃模型的形成。     

An experimental model of generalized seizures for the measurement of local cerebral glucose utilization in the immature rat. I. Behavioral characterization and determination of lumped constant.

An experimental model of status epilepticus has been developed in the immature rat by administration of pentylenetetrazol (PTZ) using repetitive, timed intraperitoneal injections of subconvulsive doses. The pattern of behavioral signs has been well characterized in each age group, i.e. 10 (P10), 14 (P14), 17 (P17) and 21 postnatal days (P21). In this model, the dose of convulsant could be adjusted as a function of interindividual sensitivity and status epilepticus lated for quite a long duration to allow the measurement of local cerebral metabolic rates for glucose (LCMRglc) by means of the [14C]2-deoxyglucose method [J. Neurochem., 28 (1977) 897-916]. To estimate LCMRglc during status epilepticus, the lumped constant (LC) was re-calculated in controls and PTZ-treated rats. The control LC was 0.54 at P10 and 0.50-0.51 at the three older ages studied (P14, P17 and P21). During status epilepticus, it increased to 0.64 in P10 rats and decreased to 0.42 and 0.40, respectively, in P17 and P21 animals. At P14, LC was not affected by seizures. The measurements of brain lactate levels showed a large 4.5-10-fold increase in PTZ-treated rats as compared to controls at all ages. The results of the present study show that the immature brain responds to sustained seizure activity in a specific way according to its postnatal age. Moreover, our results underscore the necessity of re-calculation of LC to the quantification of LCMRglc in such pathological states, particularly in immature animals.     

戊四氮点燃癫癎大鼠海马5-羟色胺能神经递质的动态研究

目的：观察戊四氮（PTZ）点燃癫癎形成过程中大鼠海马5-羟色胺（5-HT）能神经递质的变化。方法：用PTZ制作癫癎大鼠模型,将造模成功大鼠分为戊四氮急性发作组（PTZ 1组）和戊四氮慢性点燃组（PTZ 2组）,同时设立对照组（腹腔注射生理盐水）。在体微透析取样,观察大鼠行为、脑电图（EEG）和海马5-HT能神经递质的变化。结果：PTZ 1组癫癎发作时EEG自发放电逐级加重;癫癎发作时海马5-HT水平与对照组、发作前和发作后比较显著升高（P〈0.05）;海马5-羟吲哚乙酸（5-HIAA）水平差异无统计学意义;5-HT转化率（5-HIAA/5-HT）降低,差异有统计学意义（P〈0.05）。PTZ 2组点燃后大鼠出现自发癫癎发作,EEG在发作间期出现自发放电;5-HT和5-HIAA水平在点燃期、维持点燃期、对照组间比较差异有统计学意义（P〈0.05）。结论：大鼠癫癎发作时海马5-HT水平显著升高,发作后恢复正常;在癫癎形成过程中,早期5-HT水平一过性升高、PTZ点燃后和发作间期海马5-HT水平逐渐降低。     

粉防已碱对戊四唑致癫大鼠脑透析液中Glu、Asp的影响

目的:探讨钙拮抗剂粉防已碱(Tet)的抗癫痫作用机制。方法:健康SD大鼠随机分为4组:对照组、Tet组3个剂量组(15mg/kg、30mg/kg、60mg/kg)。将大鼠制成微透析模型,并收取其腹腔注射戊四唑(Pentylenetetrazol,PTZ)前后的透析液,采用高效液相色谱和荧光检测相结合的方法测定大鼠海马细胞外谷氨酸(Glu)及天冬氨酸(Asp)的浓度。结果:对照组腹腔注射PTZ后海马细胞外Glu浓度明显升高(p<0.01),Tet三个剂量组腹腔注射PTZ后同对照组比较Glu、Asp浓度明显降低(p<0.01),且似具剂量依赖性。结论:Tet的抗癫痫作用与其降低癫痫大鼠海马细胞外Glu及Asp浓度有关,对Glu的作用更为显著。     

Consequences of pilocarpine-induced recurrent seizures in neonatal rats

Accumulated evidence have shown that a series of morphological alternations occur in patients with epilepsy and in different epileptic animal models. Given most of animal model studies have been focused on adulthood stage, the effect of recurrent seizures to immature brain in neonatal period has not been well established. This study was designed to observe the certain morphological changes following recurrent seizures occurred in the neonatal rats. For seizure induction, neonatal Wistar rats were intraperitoneally injected with pilocarpine on postnatal day 1 (P1), P4 and P7. Rat pups were grouped and sacrificed at 1d, 7d, 14d and 42d after the last pilocarpine injection respectively. Bromodeoxyuridine (BrdU) was intraperitoneally administered 36h before the rats were sacrificed. BrdU single and double labeling with neuronal markers were used to analyze cell proliferation and differentiation. Nissl and Timm staining were performed to evaluate cell loss and mossy fiber sprouting. Rats with neonatal seizures had a significant reduction in the number of Bromodeoxyuridine-(BrdU) labeled cells in the dentate gyrus compared with the control groups when the animals were killed either 1 or 7 days after the third seizure (P<0.05) but there was no difference between two groups on P21. On the contrary, BrdU-labeled cells significantly increased in the experimental group compared with control group on P49 (P<0.05). The majority of the BrdU-labeled cells colocalized with neuronal marker-NF200 (Neurofilament-200). Nissl staining showed that there was no obvious neuronal loss after seizure induction over all different time points. Rats with the survival time of 42 days after neonatal seizures developed to increased mossy fiber sprouting in both the CA3 region and supragranular zone of the dentate gyrus compared with the control groups (P<0.05). Taken together, the present findings suggest that synaptic reorganization only occurs at the later time point following recurrent seizures in neonatal rats, and neonatal recurrent seizures can modulate neurogenesis oppositely over different time window with a down-regulation at early time and up-regulation afterwards.     

Spatiotemporal analysis of Fos expression associated with cocaine- and PTZ-induced seizures in prenatally cocaine-treated rats.

We previously reported that prenatal cocaine exposure (40 mg/kg s.c., E10-E20) increased susceptibility to convulsant-induced seizures later in life, with female rats becoming more sensitive to seizures induced by cocaine and pentylenetetrazol (PTZ), and males more sensitive to PTZ-induced seizures (Snyder-Keller and Keller, 1995, 2000). In order to determine the locus of enhanced seizure susceptibility in the brains of prenatally cocaine-treated rats, we examined the distribution and density of Fos-immunoreactive cells after cocaine- and PTZ-induced seizures in mature rats. Subconvulsive cocaine doses induced c-fos in cortical areas as well as densely dopamine-innervated regions such as striatum and nucleus accumbens. Following cocaine-induced seizures, intense c-fos induction was observed in piriform cortex, amygdala, and hippocampus. Quantification of the number of Fos-immunoreactive cells in the brains of prenatally cocaine-treated versus prenatally saline-treated rats revealed differences in piriform cortex and amygdala that were indicative of a lower threshold in prenatally cocaine-treated female rats. Following PTZ-induced seizures, the same pattern of limbic structures were recruited with increasing seizure severity. Only females exhibited changes in the number of Fos-immunoreactive cells as a result of prenatal cocaine treatment. Pretreatment with the noncompetitive NMDA antagonist MK-801 blocked both cocaine- and PTZ-induced seizures, and Fos expression in limbic areas was also blocked. The dopamine D1 antagonist SCH 23390 blocked cocaine-induced seizures and associated c-fos induction, but not PTZ-induced seizures or Fos. Examination of the pattern of Fos expression at 15-20 min postseizure revealed that the initial site of c-fos induction associated with PTZ-induced seizures appeared to be the piriform cortex, whereas cocaine-induced seizures induced early expression in both piriform cortex and lateral amygdala. These findings suggest that neural alterations residing in the piriform cortex and amygdala are likely to account for the increased seizure susceptibility of prenatally cocaine-treated rats.