不同剂量托吡酯对癫癎大鼠临床发作与脑电活动的影响

目的:观察不同剂量托吡酯对癫癎大鼠临床发作及脑电活动的影响。方法:选取雄性健康Wistar大鼠60只制作杏仁核点燃模型,然后用托吡酯(分20、40、80 mg／kg三组)进行灌胃,记录用药后杏仁核后放电阈值、皮层及杏仁核后放电持续时间及大鼠双前肢抽动时间。结果:托吡酯灌胃后相同强度电刺激点燃大鼠所需刺激次数明显增加;托吡酯(40、80 mg／kg)灌胃后4 h,杏仁核后放电阈值升高、杏仁核及皮层后放电时程缩短、双前肢抽动时间缩短。结论:托吡酯可明显缩短杏仁核点燃大鼠癫 癎发作时间,缩短杏仁核及皮层后放电持续时间,升高杏仁核后放电阈值。     

Different Patterns of Induction of Fibroblast Growth Factor-2 and Brain-Derived Neurotrophic Factor Messenger RNAs During Kindling Epileptogenesis, and Development of a Herpes Simplex Vector for Fibroblast Growth Factor-2 Gene Transfer in Vivo

Summary: Purpose : To investigate the gene expression patterns of brain-derived neurotrophic factor (BDNF) and fibroblast growth factor-2 (FGF-2) in the kindling model, and to construct a replication-defective herpes simplex virus vector to induce expression of FGF-2 in vivo.
Methods : RNase protection assay and herpes simplex virus vector (TH FGF-2) deleted in the immediate-early genes ICP4, ICP22, and ICP27, with FGF-2 inserted in tk under the control of the human cytomegalovirus immediate-early promoter.
Results : A single kindling stimulation did not modify BDNF gene expression, whereas it increased FGF-2 messenger RNA (mRNA) levels in the hippocampus, the cortex, and the hypothalamus. BDNF and FGF-2 gene expression were not altered in kindled animals left unstimulated for 1 week. In contrast, kindled seizures produced a great increase in hippocampal and cortical BDNF mRNA levels, but FGF-2 mRNA was increased only in the ipsilateral cortex. Infection of Vero cells with TH FGF-2 resulted in a long-lasting increase in FGF-2 levels. Protein extracts of infected cells induced neuronal differentiation of PC12 cells, indicating that the newly synthesized FGF-2 was biologically active. Robust transient transgene expression was observed in the rat hippocampus after inoculation with TH FGF-2 in the absence of significant toxicity.
Conclusions : BDNF and FGF-2 are recruited at different stages of kindling and, accordingly, may play different roles in the adaptive changes taking place during epileptogenesis. TH FGF-2 is suitable for studies of FGF-2 involvement in kindling epileptogenesis.     

A study of the action of valproic acid on the kindling effect.

The effect of an antiepileptic drug, valproic acid (VPA), on an experimental form of epilepsy, the kindling phenomenon, is described. In cat, 50 mg/kg i.p. per day is sufficient to block the progressive establishment of generalized seizures produced normally by repetitive electrical stimulation of the amygdala. However, a focal afterdischarge persists during the entire treatment. Higher doses (75-150 mg/kg) are necessary to protect the animal against the generalized tonic-clonic seizure when the kindling phenomenon is established. These effects and the action of barbiturates, which was also tested, seem to attribute to VPA a complex role in the mechanism of this action.     

难治性癫痫大鼠脑内多药耐药相关蛋白1表达的研究

目的 研究杏仁核电刺激点燃的难治性癫痫大鼠脑内多药耐药相关蛋白1（multidrug resistant-associated protein 1 MRP1）表达的情况.方法 建立杏仁核电刺激点燃的难治性癫痫大鼠模型,用免疫组织化学及免疫蛋白印记（western blot）的方法,分析比较MRP1蛋白在癫痫模型组与正常对照组的表达.结果 药物难治性癫痫大鼠组脑内多药耐药相关蛋白的表达显著高于正常对照组（P〈0.01）.在癫痫大鼠脑内广泛分布的MRP1免疫阳性细胞主要为毛细血管内皮细胞和星形胶质细胞.结论 癫痫大鼠脑内高表达的MRP1参与了难治性癫痫的耐药机制.     

Epileptogenesis and the Immature Brain

Summary: Epidemiological studies indicate that the incidence of seizures is highest early in life. This report discusses the experimental data derived from studies of focal epileptogenesis of the immature brain in tandem with ongoing maturational changes. During development, neurons have characteristic neurophysiological properties. Local interictal discharges are long in duration, lack a stereotypic morphology, and have limited fields. Yet the immature brain is very susceptible to the development of bilateral, although asynchronous, seizures and status epilepticus induced by amygdala kindling or by convul-sant drugs. This increased seizure susceptibility may be due to a functional immaturity of a substantia nigra, GABA-sensitive output system. The morbidity of convulsions occurring early in life may not be as grave as previously thought in terms of subsequent acquisition of "normal" developmental milestones. The propensity to develop recurrent convulsions in adulthood is not related to the severity of a single seizure in infancy. Although multiple severe seizures may predispose animals to the development of seizures later in life, this is not a unique feature of the immature brain, since it also occurs in the adult brain. Finally, there is evidence that the immature brain may respond to anticonvulsant drugs differently from its mature counterpart; these findings emphasize the need to develop new antiepileptic therapies that take into account the maturational state of the brain.     

Behavioral depression induced by an amygdala seizure and the opioid fentanyl was mediated through the nucleus accumbens

Purpose:  To study the behavioral depression induced by a generalized limbic seizure and by an opioid. The hypothesis that an opioid fentanyl and an amygdala-evoked seizure induced behavioral depression through the nucleus accumbens was tested.
Methods:  The behavioral depression induced by an amygdala-kindled seizure was studied in fully kindled rats, with or without prior injection of fentanyl (0.05 mg/kg, s.c.). Local infusion of a nonspecific opioid antagonist, naloxone, or saline, was made bilaterally in the nucleus accumbens. The durations of loss of righting reflex (LORR), loss of tail-pinch response, and catalepsy were assessed.
Results:  Fentanyl induced an LORR following a generalized kindled seizure. The combination of fentanyl and a generalized seizure, as compared to fentanyl alone or a generalized seizure alone, resulted in a prolonged duration of LORR, catalepsy, and loss of tail pinch response. Infusion of naloxone as compared to saline in the nucleus accumbens reduced the duration of catalepsy and LORR induced by fentanyl, with or without a generalized seizure.
Conclusions:  Postictal depression that follows a generalized kindled seizure enhanced the behavioral effects of the opioid fentanyl. Network synaptic depression induced by the seizure acted synergistically with fentanyl to produce analgesia, catalepsy, and LORR, in part through the nucleus accumbens.     

The anticonvulsant effects of progesterone and 5alpha-dihydroprogesterone on amygdala-kindled seizures in rats

PURPOSE: Progesterone has been shown to be anticonvulsant in several animal seizure models. The purpose of the present study was to investigate the anticonvulsant actions of progesterone and its primary metabolite 5alpha-dihydroprogesterone in the amygdala kindling model. METHODS: Female Wistar rats were implanted in the right basolateral amygdala with a long-term, bipolar electrode. The subjects were kindled to 30 stage 5 seizures and stability tested. Multiple doses of progesterone and 5alpha-dihydroprogesterone were then tested for anticonvulsant activity against focal electrographic and generalized convulsive kindled seizures. The time course of progesterone's anticonvulsant action also was examined. RESULTS: Progesterone had a median effective dose (ED50) of 103 mg/kg against generalized convulsions at 15 min after injection. Subjects were not sedated at the time of seizure testing, although sedation developed later (40-60 min after injection). In time-course experiments, it was found that 120 mg/kg of progesterone caused complete suppression of the generalized convulsion from 20 to 160 min after injection. Suppression of the focal discharge also was seen in some animals between 20 and 160 min. 5alpha-dihydroprogesterone had an ED50 of 2.9 mg/kg against generalized kindled convulsions and an ED50 of 4.3 mg/kg against focal afterdischarge 15 min after injection. 5alpha-dihydroprogesterone did not produce sedation 15 min after injection, or at any later time interval. CONCLUSIONS: Progesterone is anticonvulsant only at high doses when tested against amygdala kindled seizures. 5alpha-dihydroprogesterone is considerably more potent than progesterone. At low, nonsedative doses, it was effective against both the kindled amygdala focal afterdischarge and the generalized convulsion.     

An animal model of generalized nonconvulsive status epilepticus: immediate characteristics and long-term effects

Absence seizures are traditionally believed to have no significant long-term neurological consequences, but few basic scientific studies have examined the effects of absence seizures on neuronal function, especially regarding absence status epilepticus. We developed a model of generalized nonconvulsive status epilepticus (GNCSE) in rats to study behavioral, functional, and histological effects of GNCSE. Using repetitive timed injections of low-dose pentylenetetrazol (PTZ), a state of prolonged behavioral arrest and immobility associated with frequent generalized spike-wave discharges on EEG could be induced for hours, consistent with GNCSE. GNCSE occurred reproducibly in adult rats, but surprisingly not in juvenile rats or adult mice. There was no evidence of pathological damage following GNCSE using Fluoro-Jade B and Cresyl Violet histological methods. Although a transient, subtle deficit in place learning occurred in PTZ-treated rats, there were no long-term behavioral effects of GNCSE on spatial learning or sensorimotor function. However, 1 week after a single episode of GNCSE, there was an increase in absence seizures in response to a repeat dose of PTZ compared to controls. These results indicate that an animal model of GNCSE can be generated and that even in the absence of overt neuronal damage, GNCSE may produce functional changes in neurons that alter electrical excitability of neural circuits.     

Glutamatergic activation of the amygdala differentially mimics the effects of audiogenic seizure kindling in two substrains of genetically epilepsy-prone rats

Comparisons of neuronal network mechanisms in closely related inherited seizure models are providing novel insights into epileptogenic pathophysiology. Genetically epilepsy-prone rats (GEPRs) exist in two substrains that inherit long-term susceptibility to behaviorally distinct audiogenic seizures (AGS). GEPR-3s exhibit generalized clonic AGS, while GEPR-9s exhibit generalized tonic AGS. After AGS kindling the tonic AGS of GEPR-9s is followed by generalized posttonic clonus (PTC), while the generalized clonic AGS is followed by facial and forelimb (F&F) clonus in GEPR-3s. PTC and F&F clonus are very rare in GEPRs before AGS kindling. The neuronal network subserving AGS in GEPR-9s lies exclusively in brainstem sites, but amygdala (AMG) and other sites are recruited into the network after AGS kindling. The present study attempted to mimic the effects of AGS kindling by bilaterally microinjecting subconvulsive doses of N-methyl-D-aspartate (NMDA) into the AMG of nonkindled GEPRs. NMDA (10 nmol/side) microinjected into AMG reversibly induced susceptibility to F&F clonus immediately following generalized clonic AGS in most nonkindled GEPR-3s. NMDA (7.5 nmol/side), microinjected into AMG temporarily induced susceptibility to generalized PTC immediately following tonic AGS in most nonkindled GEPR-9s. No seizures were induced in normal rats by these treatments, and no seizures were seen in GEPRs with these NMDA doses except those induced by acoustic stimuli. These findings support a critical role in AGS kindling for the AMG in the neuronal networks for both forms of AGS. However, the behavioral effect of the treatment was different in the two AGS substrains, suggesting interrelated but not identical pathophysiological mechanisms in these closely related epilepsy models.