Altered expression of voltage-gated potassium channel 4.2 and voltage-gated potassium channel 4-interacting protein, and changes in intracellular calcium levels following lithium-pilocarpine-induced status epilepticus

The A-type voltage-gated potassium channels (Kv4) have been proved to play a major role as modulators of somatodendritic excitability. Recent studies indicate that neuronal hyperactivity in epilepsy is associated with changes in Kv4. However, the precise regulation of Kv4 in the development of epilepsy and its underlying mechanism remain unclear. In this study, we investigated whether the expression of the Kv4.2 channel and of its major modulator, voltage-dependent potassium channel-interacting protein (KChIP1), is altered following lithium-pilocarpine induced status epilepticus (SE) and the chronic-epilepsy phase in the rat model. We found that Kv4.2 and KChIP1 expression was transiently up-regulated following SE, whereas it was down-regulated during the chronic phase: this was most prominent in the CA1 and CA3 regions. The time-course analysis of the protein expression level showed that the peak Kv4.2 up-regulation was between 6 and 24 h after SE, whereas KChIP1 expression was increased earlier and for a shorter period. The temporospatial changes in Kv4.2 were very similar to those of its major modulator KChIP1. We compared the difference in 4-aminopyridine (4-AP)-induced intracellular calcium ([Ca(2+)]i) elevation between model and control brain slices. The results showed that the [Ca(2+)]i elevation induced by the Kv4 channel blocker 4-AP was aggravated and prolonged in the model slice after SE. The functional relevance of these changes in Ca(2+) homeostasis and Kv4.2 and KChIP1 expression may be associated with intrinsic neuronal excitability regulation and epileptogenesis.     

Status epilepticus induces a TrkB to p75 neurotrophin receptor switch and increases brain-derived neurotrophic factor interaction with p75 neurotrophin receptor: an initial event in neuronal injury induction

In neuronal cultures it has been demonstrated that neurotrophins can elicit neuronal death through the p75 neurotrophic receptor (p75ntr) in the absence of concomitant Trk signaling. However, it was suggested that p75ntr induces neuronal death after status epilepticus (SE) in neuronal populations that express relatively high quantities of tropomyosin receptor kinase B (TrkB). Here, using Western blot and immunohistochemistry analyses in the hippocampus, we found that 3-h SE caused a remarkable decrease in TrkB expression and phosphorylation, and a significant increase in p75ntr. TrkB modification occurs before the overexpression of the tumor suppressor protein p53, accompanies the cell damage taking place in the dentate gyrus, and precedes the CA1 neuronal injury as assessed by Fluoro-Jade B and Nissl staining. Co-immunoprecipitation of brain-derived neurotrophic factor (BDNF) or its immature form proBDNF showed increased interaction with p75ntr after its binding to TrkB was reduced. Interestingly, proBDNF also increases its binding with p75ntr after seizures that do not cause neuronal death (animals injected with pilocarpine that fail to enter SE). However, in those animals, TrkB protein levels remained unchanged and its phosphorylation increased. Our results indicate an intrinsic capacity of neurons in vivo to modify final neurotrophin output by changing the proportion of their receptors' expression and the receptors' interaction with their ligands. These early events support the idea that neurotrophins may be involved in the induction of neuronal death in vivo under pathological conditions.     

Vascular endothelial growth factor is up-regulated after status epilepticus and protects against seizure-induced neuronal loss in hippocampus

Vascular endothelial growth factor (VEGF) is a protein factor which has been found to play a significant role in both normal and pathological states. Its role as an angiogenic factor is well-established. More recently, VEGF has been shown to protect neurons from cell death both in vivo and in vitro. While VEGF's potential as a protective factor has been demonstrated in hypoxia-ischemia, in vitro excitotoxicity, and motor neuron degeneration, its role in seizure-induced cell loss has received little attention. A potential role in seizures is suggested by Newton et al.'s [Newton SS, Collier EF, Hunsberger J, Adams D, Terwilliger R, Selvanayagam E, Duman RS (2003) Gene profile of electroconvulsive seizures: Induction of neurotrophic and angiogenic factors. J Neurosci 23:10841-10851] finding that VEGF mRNA increases in areas of the brain that are susceptible to cell loss after electroconvulsive-shock induced seizures. Because a linear relationship does not always exist between expression of mRNA and protein, we investigated whether VEGF protein expression increased after pilocarpine-induced status epilepticus. In addition, we administered exogenous VEGF in one experiment and blocked endogenous VEGF in another to determine whether VEGF exerts a neuroprotective effect against status epilepticus-induced cell loss in one vulnerable brain region, the rat hippocampus. Our data revealed that VEGF is dramatically up-regulated in neurons and glia in hippocampus, thalamus, amygdala, and neocortex 24 h after status epilepticus. VEGF induced significant preservation of hippocampal neurons, suggesting that VEGF may play a neuroprotective role following status epilepticus.     

氯化锂-重复低剂量匹罗卡品致大鼠癫痫模型制作

目的:建市氯化锂一重复低剂量匹罗卡品致痫大鼠模型.方法:雄性成年sD大鼠173只.随机分为对照组、非药物干预组和药物干预组.氯化锂3mEq/kg腹腔注射(IP),19h后给予低剂量匹罗卡品10mg/kg,每隔30min 1次,重复2-4次.观察大鼠行为、脑电、模型成功率、死亡率、自发性癫痫发作及其潜伏期和发作的严重程度.结果:氯化锂-重复低剂量匹罗卡品大鼠癫痫模型在匹罗卡品1～4剂后发生癫痫持续状态,痫性发作距离注射时间平均为16min,成功率73%,匹罗卡品用量平均25.9mg/kg,持续90min被终止者死亡率低于10%.自发性癫痫发作平均每天2.4～5.7次,潜伏期平均40天.发作程度均达到Ⅲ级以上的痫性发作,绝大多数为Ⅳ/Ⅴ级,脑电类似人类颞叶癫痫.对照组大鼠均为0级发作.结论:氯化锂-重复低剂量匹罗卡品诱导的大鼠癫痫模型具有制作方便、致痫成功率高和动物死亡率低特点,同人类癫痫持续状态和颞叶癫痫有相似的行为和脑电图改变.     

Pilocarpine-induced cholinergic sweat secretion compared with emotional sweat secretion in atopic dermatitis

We studied pilocarpine-induced cholinergic sweating, emotional sweating and sympathetic reflex sweating in atopic dermatitis (AD) patients. Secreted sweat was measured both with equipment that continuously records sweat rate and with a filter paper method that measures sweat weight absorbed. Comparison of the two methods revealed that the filter paper method underestimated the sweat secretion in AD patients. While AD patients showed no significant abnormalities in emotional sweating and sympathetic reflex sweating, the duration of pilocarpine-induced sweating was prolonged. The time from the maximal sweat rate until the sweat rate fell to half of the maximal rate was significantly longer in AD patients than in control subjects. In contrast, the time from the beginning of sweat secretion until the maximal sweat rate was not significantly different between AD patients and control subjects. There was no significant difference between AD patients and control subjects in sweat volume secreted in 20 min after pilocarpine iontophoresis. In AD patients, the total sweat volume secreted after pilocarpine iontophoresis was greater than in control subjects, although not significantly. These results suggest that the system of deactivation of pilocarpine-induced sweat secretion is impaired in AD patients whereas the activation system is not altered.     

参蒲汤抗癫痫效应及其与氨基酸水平相关性的研究

[目的]观察参蒲汤的抗癫痫效应,并初步探讨了抗癫痫效应与脑组织氨基酸水平之间的关系。[方法]利用匹罗卡品致癫痫动物模型,并通过高效液相色谱法测定脑组织氨基酸水平,比较行为学和生化学两方面变化。[结果]参蒲汤具有较好的抗匹罗卡品诱导的顽固性癫痫作用和较强的终止癫痫持续状态(SE)发作的作用;并可抑制致惊厥条件下谷氨酸的升高,提高致惊厥条件下和惊厥条件下脑组织的GABA水平。[结论]参蒲汤有较好的抗癫痫效应,其发挥抗癫痫效应与谷氨酸水平的降低和GABA水平升高密切相关。     

Neurogenesis in the epileptic brain: a brief overview from temporal lobe epilepsy

Dentate granule cell neurogenesis persists throughout life in the hippocampus of mammals. Alterations in this process occur in many neurological diseases, including epilepsy. Among the different types of epilepsy, the most frequent is temporal lobe epilepsy (TLE). Therefore, a number of laboratory studies use animal models of TLE to observe the fate of neuronal cells after seizures. Hippocampal neurogenesis is very sensitive to physiological and pathological stimuli. Seizures, as pathological stimuli, alter both the extent and the pattern of neurogenesis, which is associated with cognitive function. Various alterations in neurogenesis are observed depending on the amount of time that has elapsed after the seizures. In acute seizures, neurogenesis generally increases, whereas in chronic epilepsy, neurogenesis decreases. Moreover, several methods currently used for the treatment of brain disorders such as TLE can also have significant impacts on cognitive functions. This review is focused on the recent findings regarding neurogenesis in animal models of TLE.