POSSIBLE PARTICIPATION OF NMDA AND GLYCINE RECEPTORS BUT NOT GABAA RECEPTORS IN ENFLURANE-INDUCED OPISTHOTONUS IN MICE

1. We previously reported that volatile anaesthetics produce incidences of a transient opisthotonus in mice, a sign of CNS stimulation. This study was performed to investigate mechanisms by which enflurane-induced opisthotonus (EIO) occurs. 2. The effects of pretreatment of N-methyl-d-aspartate (NMDA) antagonists dizocilpine (MK-801; DIZ) and ketamine (KET), GABA_A antagonists picrotoxin (PIC), pentylenetetrazol (PTZ) and glycine antagonist strychnine (STR) on the incidence of EIO were determined. Prior to exposure to 2.0% enflurane in air, male ddN mice were given intraperitoneal injections of 0.2 mL saline (control), 0.5–5.0 mg/kg DIZ, 20–80 mg/kg KET, 2.9 mg/kg PIC, 40.0 mg/kg PTZ and 0.75 mg/kg STR. After the injection, the behavioural state of the mice was observed for 20 min (the pre-enflurane period). During the exposure to enflurane the time for immobilization, that is, anaesthetic induction time (IT), and the incidence of EIO were measured. 3. Dizocilpine (1.0–5.0 mg/kg) and KET (80 mg/kg) significantly (P<0.01) reduced both the incidence of EIO and IT in a dose-dependent manner. During the pre-enflurane period DIZ produced incidences (5–40%) of transient seizures in a dose-dependent manner, while KET did not induce them at all. The two GABA_a antagonists had no detectable effect on the EIO. Strychnine significantly enhanced the EIO. These CNS stimulants resulted in a 3–10% incidence of transient seizure and/or opisthotonus during the pre-enflurane period, but there was no correlation between DIZ-induced seizure and EIO. 4. These results suggest that the EIO is mediated by the NMDA and the STR-sensitive glycine receptors, but not the GABA_A receptor. We speculate that DIZ acts on the NMDA-receptor and/or disrupts the balance between the inhibitory and the excitatory systems.     

Vagus Nerve Stimulation Induces a Sustained Anticonvulsant Effect

Summary: Purpose: Stimulation of the vagus nerve can effectively abort several types of experimentally induced seizures in animals when administered near the time of seizure onset. Indirect evidence from human trials and animal studies suggests that the anticonvulsant effects of vagus nerve stimulation (VNS) extend beyond the duration of stimulation. We used the pentylenetetrazol model to determine whether VNS exerts a persistent anticonvulsant effect.
Methods: VNS (1 mA, 30 Hz, 500 μs pulse width) was administered continuously for 0, 1, or 60 min, or intermittently (30 s on, 5 min off) for 60 min, to awake and freely moving animals. After the end of stimulation, pentylenetetrazol (50 mg/kg i.p.) was administered to induce seizures. Time-course studies were also performed, consisting of 60 min of VNS followed by pentylenetetrazol injection after 0, 3-, 5-, and 10-min intervals.
Results: The greatest anticonvulsant effect occurred after 60 min of continuous VNS, which prevented convulsions in four of 12 rats and reduced significantly seizure duration, the total number of seizures, and number of tonic seizures. Intermittent VNS was less effective than continuous stimulation for 60 min, but more effective than that for 1 min. The anticonvulsant effect declined in a time-dependent fashion after discontinuation of VNS, with return to nonstimulated control values by 10 min.
Conclusions: The results of this study verify a persistent VNS-induced anticonvulsant effect and indicate that its efficacy is dependent on the cumulative stimulus duration.     

戊四氮诱发大鼠全身强直-阵挛性癫痫发作诱导丘脑c-fos癌基因表达

首次运用Fos癌蛋白抗体免疫组化法详细研究了戊四氮诱发大鼠全身强直-阵挛性癫痫发作诱导丘脑c-fos癌基因表达的动态分布。主要结果是:腹腔内注入戊四氮诱导大鼠癫痫发作后0.5h,丘脑室旁核出现低密度的Fos-免疫阳性(Fos-ir)细胞核标记;3h时,中等密度的Fos-ir标记扩布至大部分丘脑中线和板内核群及网状核;6h时,所有上述丘脑核群的Fos-ir标记普遍增为中等至高密度。结合文献报道,上述结果提示:丘脑室旁核很可能是戊四氮诱发大鼠全身强直-阵挛性癫痫发作的重要起源部位之一;丘脑中线和板内核群及网状核很可能在此种癫痫发作的病理生理机制中起重要作用。     

Pharmacodynamics of Phenobarbital Anesthesia and Pentylenetetrazol-Induced Maximal Seizures in a Rat Model of Neoplastic Spinal Cord Compression

The purpose of this investigation was to determine whether paraplegia induced by neoplastic cord compression affects the pharmacodynamics of phenobarbital general anesthesia or of pentylenetet-razol (PTZ)-induced convulsions. Paraplegic rats harboring a thora-columbar epidural tumor, or an identical hindlimb tumor mass, received an i.v. infusion of phenobarbital until the onset of anesthesia. At that point, the phenobarbital concentrations in the CSF and serum were measured. Similarly, PTZ was infused until the onset of maximal seizures. It was found that changes related to systemic tumor growth and newly developed paraplegia due to neoplastic spinal cord compression did not attenuate the pharmacodynamics of phenobarbital. However, sustained paraplegia of 4 days duration reduced CNS sensitivity to the hypnotic action of the barbiturate as evidenced by the higher cerebrospinal fluid phenobarbital concentration required to induce anesthesia (170 ± 31 vs 125 ± 20 mg/L; P < 0.05). On the other hand, sustained paraplegia did not affect brain threshold concentration for PTZ-induced seizures.     

Cocaine and "pharmacological kindling" in the rat

The concept of "pharmacological kindling" has been used to explain the behavioral sensitization to cocaine produced by repeated administration of subconvulsive doses. This idea was tested by the repeated administration of cocaine to rats followed by electrical kindling of the olfactory bulb (a site at which cocaine has prominent electrophysiologic effects). No significant effect of cocaine on kindling was found. The relationship of this finding to studies using other drugs is discussed.     

鼠神经生长因子对癫痫幼鼠脑保护作用的研究

目的探讨鼠神经生长因子(m NGF)对癫痫(EP)幼鼠海马金属硫蛋白Ⅰ/Ⅱ(MTⅠ/Ⅱ)和细胞色素C(Cyt C)表达的影响。方法 50只日龄19 d的SD大鼠,随机分为对照组,EP组,m NGF低、中、高剂量组,每组10只。对照组每日予生理盐水注射;EP组腹腔注射戊四氮40 mg/(kg·d),连续21 d;m NGF低、中、高剂量组给予等剂量戊四氮21 d后,分别予m NGF 500 AU/(kg·d)、1 000 AU/(kg·d)、2 000 AU/(kg·d)肌肉注射,连续7 d。观察幼鼠体质量及行为学表现,免疫组织化学法检测海马MTⅠ/Ⅱ和Cyt C阳性细胞表达,实时荧光定量PCR法检测MTⅠ和Cyt C m RNA表达。结果对照组、EP组以及m NGF低、中、高剂量组幼鼠海马的MTⅠ和Cyt C m RNA表达以及MTⅠ/Ⅱ和Cyt C阳性细胞数的差异有统计学意义(F=15.98~105.76,P均=0.000)。两两比较发现,EP组的MTⅠ和Cyt C m RNA表达明显升高,MTⅠ/Ⅱ和Cyt C阳性细胞数明显增多,均分别高于对照组和m NGF低、中、高剂量组,差异有统计学意义(P均0.05);低剂量组的MTⅠ和Cyt C m RNA表达高于中、高剂量组,而MTⅠ/Ⅱ和Cyt C阳性细胞数高于高剂量组,差异有统计学意义(P均0.05);中剂量与高剂量组间MTⅠ和Cyt C m RNA表达以及MTⅠ/Ⅱ和Cyt C阳性细胞数的差异无统计学意义(P均0.05)。结论 MTⅠ/Ⅱ作为一种应激性蛋白,与Cyt C共同参与了癫痫的过程。m NGF对癫痫后的海马有保护作用,且有剂量依赖。     

迷走神经刺激对戊四氮癫痫大鼠海马区γ-GABA、Glu和脑电变化

目的 观察VNS对正常大鼠和戊四氮(PTZ)致癫痫大鼠的脑电图的影响,以及测定海马区GABA,GLU的变化.进一步探讨迷走神经刺激(VNS)的抗癫痫机制.方法 随机分为对照组、刺激A组、刺激B1组、刺激B2组、刺激B3组、刺激C组,各10只.分别观察脑电图和测定海马GABA、GLU的变化.结果 VNS可明显延长致病大鼠癫痫发作和痫波释放的潜伏期(P<0.05),减轻癫痫发作的严重程度,并能抑制皮层及海马癫痫波的释放,VNS对正常人鼠脑电图无影响.刺激各组海马GABA升高,GLU下降,组与组之间有明显差异P<0.05.结论 VNS可明显抑制PTZ诱导的大鼠癫痫.     

高频电刺激丘脑网状核对戊四氮致癫痫大鼠的作用

目的 研究高频电刺激丘脑网状核（TRN）对戊四氮致癫痫大鼠的作用.方法 通过立体定向仪在大鼠TRN埋置刺激电极,于腹腔注射1%戊四氮（65mg/kg）的同时,电刺激TRN（刺激频率分别为60Hz、80Hz及100Hz）,观察并记录癫痫发作程度和持续时间.结果 高频电刺激TRN,戊四氮致大鼠癫痫的平均发作程度、重度发作个数以及持续时间都明显减少.结论 高频电刺激TRN能够明显抑制戊四氮诱导的大鼠癫痫发作.     

托吡酯对戊四氮点燃慢性癫(癎)大鼠海马神经细胞黏附分子的影响

目的:探讨神经元活化在癫发生、发展中的作用及托吡酯对其的影响。方法:采用戊四氮制备慢性癫模型,利用托吡酯干扰,选取不同时间点,观察大鼠行为学变化及神经细胞黏附分子在海马回的表达(免疫组织化学染色)。结果:托吡酯组点燃率在27d明显低于模型组;模型组及托吡酯组神经细胞黏附分子表达增加,并随时间延长明显;而不同时间点该表达的增加程度,托吡酯组均低于模型组。结论:神经细胞黏附分子表达的增加,说明出现了神经元活化及脑可塑性变化,而托吡酯明显地抑制了该表达的增加。     

Non-canonical amino acid labeling in vivo to visualize and affinity purify newly synthesized proteins in larval zebrafish

Protein expression in the nervous system undergoes regulated changes in response to changes in behavioral states, in particular long-term memory formation. Recently, methods have been developed (BONCAT and FUNCAT), which introduce non-canonical amino acids bearing small bio-orthogonal functional groups into proteins using the cells' own translational machinery. Using the selective 'click reaction', this allows for the identification and visualization of newly synthesized proteins in vitro. Here we demonstrate that non-canonical amino acid labeling can be achieved in vivo in an intact organism capable of simple learning behavior, the larval zebrafish. We show that azidohomoalanine is metabolically incorporated into newly synthesized proteins, in a time- and concentration-dependent manner, but has no apparent toxic effect and does not influence simple behaviors such as spontaneous swimming and escape responses. This enables fluorescent labeling of newly synthesized proteins in whole mount larval zebrafish. Furthermore, stimulation with a GABA antagonist that elicits seizures in the larval zebrafish causes an increase in protein synthesis throughout the proteome, which can also be visualized in intact larvae.