不同成熟期大鼠戊四氮反复惊厥模型与癫痫发病机制研究

目的：观察新生大鼠、成熟大鼠反复惊厥后海马结构的变化及NF-κB 表达，探索未成熟脑癫痫发病机制。 方法： 对生后10 d、60 d（P10、P60）两实验组大鼠用戊四氮(PTZ)反复腹腔注射5 d，设P10、P60生理盐水对照组；硫堇染色对CA1、CA3、DG及门区神经元进行细胞计数, 观察海马神经元坏死及凋亡；免疫组化技术检测NF-κB的表达；Timm组织化学染色观察苔藓纤维发芽并评分。 结果： (1) P10实验组与对照组比较，海马齿状回、CA1、CA3区无明显神经元丢失，DG区颗粒细胞数在实验组(23.25±3.06) 多于对照组（16.25±1.58）；P60实验组CA1、CA3区神经元计数（8.22±1.88、5.62±1.68）明显少于对照组（6.31±1.50、3.62±1.40），DG区无明显差异；（2）两实验组CA3区锥体层苔藓纤维发芽均多于对照组，但P60(3.25±1.03)较P10（1.50±0.92）更明显；（3）P10、P60实验组NF-κB 表达高于对照组，且P10组较P60组更为明显（P<0.05）。 结论： 新生大鼠致痫后海马神经元无明显丢失，脑内NF-κB 表达增加，可能是未成熟脑对惊厥性脑损伤具有耐受性的重要神经生物学基础。     

锌螯合剂对匹罗卡品致痫小鼠行为学及海马神经元的影响

目的:研究锌螯合剂氯碘羟喹对匹罗卡品致痫小鼠行为学及海马神经元的影响。方法:将CD1小鼠随机分成3组,对照组小鼠腹腔注射等量的生理盐水;癫痫组小鼠腹腔注射匹罗卡品300 mg/kg;氯碘羟喹治疗组(治疗组)小鼠腹腔注射匹罗卡品300 mg/kg,30 min之后腹腔注射氯碘羟喹15 mg/kg。观察各组小鼠的癫痫发作次数。Morris水迷宫实验测定逃避潜伏期和目标象限停滞时间。应用尼氏染色计数海马神经元数量;利用免疫组织化学方法、免疫印迹结合图像分析技术检测凋亡基因caspase-3在各组小鼠海马的表达变化。结果:与对照组相比,其他2组小鼠的癫痫发作次数明显增多,发作级别明显增高;其中,治疗组小鼠的发作次数和发作级别均低于癫痫组。水迷宫实验结果显示,与对照组相比,其他2组小鼠的逃避潜伏期明显延长,目标象限停滞时间明显缩短;其中,治疗组的逃避潜伏期比癫痫组短,目标象限停滞时间比癫痫组长。其他2组小鼠海马神经元数量明显少于对照组;治疗组的海马神经元数量比癫痫组多。其他2组小鼠海马caspase-3表达明显高于对照组,阳性细胞数量增多,光密度增加;治疗组海马caspase-3的表达低于癫痫组,阳性细胞数量减少,光密度降低。结论:锌螯合剂氯碘羟喹能抑制癫痫发作,保护海马神经元,提高癫痫小鼠的学习记忆能力。     

马桑内酯致痫大鼠海马神经元丢失及化学性质的研究

为观察癫痫发作过程海马神经元丢失细胞的主要死亡方式 ,用马桑内酯建立慢性致痫大鼠模型 ,以 Nissl染色、免疫组化、TUNEL法以及后二者相结合的技术 ,对海马神经元及其中的抑制性神经元的丢失进行了分区观察、统计、分析。结果发现 :致痫组海马各区神经元较对照组明显减少 ,不同区域减少程度不同 ,以齿状回减少最为明显 ;免疫组化结果显示 ,致痫组的抑制性神经元 GABA-IR神经元、PV-IR神经元、CB-IR神经元在海马各区有不同程度的减少 ,其中 GABA-IR神经元减少最明显。在海马各区所有丢失的神经元中 ,三种抑制性神经元所占的比例不同 ;并在海马各区均可见到 TUNEL -GABA、TUNEL-PV、TU NEL-CB双重反应阳性神经元。提示 :马桑内酯所致的癫痫发作 ,可引起海马神经元丢失 ,且不同区域丢失的程度不同 ,丢失的神经元可能以凋亡方式为主 ;海马抑制性神经元 GABA-IR、PV-IR、CB-IR神经元在癫痫发作过程中也有不同程度的丢失 ,丢失很可能也是以凋亡形式为主     

NF-κB在发育鼠戊四氮反复点燃癫痫形成中的作用

目的：用NF-κB阻滞剂吡咯烷二硫基甲酸盐(PDTC)阻断NF-κB的表达，探讨核因子κB(NF-κB)在发育鼠戊四氮(PTZ)点燃癫痫形成过程中的作用。方法:生后10 d（P10）Wistar大鼠72只，随机分为PTZ组、PDTC＋PTZ组及生理盐水对照组3组，制备戊四氮反复点燃癫痫模型。观察各组大鼠行为学改变、海马各区细胞形态及细胞计数、NF-κB表达、5-溴-2-脱氧尿嘧啶核苷(BrdU)阳性细胞数和苔藓纤维发芽等指标。结果:(1)NF-κB表达，PTZ组显著高于对照组及PDTC+PTZ组（P<0.01）；(2)海马神经细胞计数，PTZ组齿状回（DG）区颗粒细胞较对照组显著增加(P<0.05)；PDTC+PTZ组CA1、CA3和门区神经元数较PTZ组均明显减少（P<0.05）；(3)DG区BrdU阳性细胞数，PTZ组和PDTC+PTZ组均较对照组显著增加（P<0.01）；PDTC＋PTZ组DG区BrdU阳性细胞数目明显较PTZ组少（P<0.01）；NF-κB吸光度值与BrdU阳性细胞数/颗粒细胞数相关性分析呈正相关，具有统计学意义（P<0.01）；（4）苔藓纤维发芽，PDTC＋PTZ组和PTZ组均有苔藓纤维发芽，两组比较没有显著差异。结论:NF-κB在发育鼠癫痫中发挥重要作用，促进海马神经元发生，保护海马神经细胞，但对苔藓纤维发芽无明显作用。     

NF-KB在发育鼠戊四氮反复点燃癫痫形成中的作用

目的:用NF-KB阻滞剂吡咯烷二硫基甲酸盐(PDTC)阻断NF-KB的表达,探讨核因子KB(NF-KB)在发育鼠戊四氮(PTZ)点燃癫痫形成过程中的作用.方法:生后10 d(P10)Wistar大鼠72只,随机分为PTZ组、PDTC PTZ组及生理盐水对照组3组,制备戊四氮反复点燃癫痫模型.观察各组大鼠行为学改变、海马各区细胞形态及细胞计数、NF-KB表达、5-溴-2-脱氧尿嘧啶核苷(BrdU)阳性细胞数和苔藓纤维发芽等指标.结果:(1)NF-KB表达,PTZ组显著高于对照组及PDTC PTZ组(P<0.01);(2)海马神经细胞计数,PTZ组齿状回(DG)区颗粒细胞较对照组显著增加(P<0.05);PDTC PrZ组CAI、CA3和门区神经元数较PTZ组均明显减少(P(0.05);(3)DG区BrdU阳性细胞数,PTZ组和PDTC PTZ组均较对照组显著增加(P<0.01);PDTC PTZ组DG区BrdU阳性细胞数目明显较PTz组少(P<0.01);NF-KB吸光度值与BrdU阳性细胞数／颗粒细胞数相关性分析呈正相关,具有统计学意义(P<0.01);(4)苔藓纤维发芽,PDTC PTz组和PTZ组均有苔藓纤维发芽,两组比较没有显著差异.结论:NF-KB在发育鼠癫痫中发挥重要作用,促进海马神经元发生,保护海马神经细胞,但对苔藓纤维发芽无明显作用.     

听源性惊厥点燃诱导海马结构神经细胞死亡

目的　检测听源性惊厥单次发作及惊厥点燃发作后 ,易感大鼠海马结构内是否出现神经细胞死亡现象 ,并对细胞死亡的相关机制进行初步分析。　方法　建立听源性惊厥点燃模型 ,以HE染色和免疫细胞化学染色方法 ,检测单次发作大鼠和点燃发作大鼠海马结构内死亡细胞的分布 ,以及凋亡相关蛋白Bcl 2和Bax的表达情况。　结果　听源性惊厥单次发作后 ,海马内未见明显细胞死亡现象 ;点燃后 ,海马CA1 、CA2 、CA4 区锥体细胞层及齿状回颗粒细胞层出现大量核固缩、胞浆嗜酸性变的死亡神经元 ;点燃组海马CA2 区及CA4 区内Bax免疫阳性产物校正光密度 (CA)值较对照组显著增高。　结论　听源性惊厥点燃可诱导海马结构大量神经元死亡 ,凋亡可能是细胞死亡的形式之一     

体外切割损伤脊髓神经元对其Fos、ChAT及GAD表达的影响

目的:研究切割损伤对体外培养脊髓神经元Fos、胆碱乙酰转移酶(ChAT)及谷氨酸脱羧酶(GAD)表达的影响。方法:脊髓神经元纯化培养后分别计数碘化丙啶(PI)阳性细胞数和微管相关蛋白2(MAP2)阳性细胞数,决定脊髓神经元纯度。根据本实验室已建立的损伤模型,对原代纯化培养脊髓神经元进行切割损伤。通过免疫组化及WesternBlot方法比较神经元损伤前后Fos、ChAT和GAD表达的变化情况。结果:脊髓神经元纯化培养后纯度达到92%。免疫组化及WesternBlot显示,切割损伤组与正常组相比,Fos、GAD表达上调,而ChAT表达降低。结论:Fos、GAD和ChAT可能参与脊髓神经元急性损伤及随后的修复过程,其生物学意义有待进一步探讨。     

碱性成纤维细胞生长因子对局灶性脑缺血大鼠脑组织C/EBP同源蛋白表达的影响

目的:研究大鼠脑缺血再灌注后对C/EBP同源蛋白(C/EBP homogous protein,CHOP)表达的影响,探讨碱性成纤维细胞生长因子(bFGF)对脑组织缺血再灌注神经元CHOP的调节作用及机制.方法:应用线栓法制作大鼠局灶性脑缺血再灌注模型,大脑中动脉阻塞2h再灌注损伤12 h,采用TUNEL法、免疫组织化学方法检测海马及皮质内神经元凋亡和CHOP的表达.结果:Sham组海马及皮质偶见凋亡细胞,皮质及海马神经元内少见CHOP免疫反应阳性细胞;I/R组海马及皮质神经元凋亡增加,缺血再灌注损伤后皮质及海马神经元内CHOP阳性表达高于假手术组.bFGF组海马及皮质神经元凋亡减少,皮质及海马神经元内CHOP表达较I/R组减少.结论:bFGF减少缺血神经元凋亡,抑制脑缺血诱导的CHOP表达,对脑缺血再灌注海马及皮质神经元具有保护作用.     

记忆增强肽对去卵巢大鼠行为和海马神经元NT—3、NF表达的影响

研究记忆增强肽是否能提高去卵巢大鼠学习、记忆功能以及它对海马区神经营养素－3（NT－3）、神经丝蛋白（NF）神经元表达的影响。随机分三组,正常对照组,去卵巢对照组和去卵巢＋记忆增强肽防治组,进行水迷宫测试和NT－3、NF免疫组化染色。发现去卵巢＋记忆增强肽防治组游完全程的时间及错误反应次数均较去卵巢对照组少（P＜0．05）,海马区神经元NT－3、NF的表达与正常大鼠相似,阳性细胞计数显著高于去卵巢对照组,平均灰度（免疫组化染色深,平均灰度数值小）显著低于去卵巢对照组（P＜0．05）。均提示记忆增强肽具有防治神经元退变的作用。     

高血糖加重缺血性脑损伤

目的：探讨高血糖对脑缺血损伤的影响。方法：采用大鼠高血糖全脑缺血模型,用HE和TUNEL染色,对比检测脑细胞损伤和凋亡。结果：高血糖组在缺血再灌注后与血糖正常组相比,纹状皮质脑水肿和神经元变性、死亡明显加重;海马CA1区损伤神经元计数无显著性差异;海马CA3区损伤神经细胞数明显多于血糖正常组。TUNEL染色可见,在纹状皮质、海马CA1区和CA3区高血糖组和血糖正常组阳性细胞明显多于对照组;在缺血或再灌注后,正常血糖组和高血糖组的TUNEL阳性细胞数均无显著性差异。结论：高血糖可加重缺血引起的神经元损伤。     

难治性颞叶癫癎患者海马病理研究

目的:探讨海马硬化和难治性颞叶癫的因果关系。方法:对8例海马硬化患者和7例非海马硬化患者临床资料、手术疗效和海马病理改变进行对比和相关分析。结果:海马硬化组较非海马硬化组病程长,疗效显著,疗效分级与最初脑损伤发生年龄呈正相关。海马硬化组和非海马硬化组均有CA1,CA3锥体细胞和颗粒细胞脱失,海马硬化组更明显。门区神经元脱失仅在海马硬化组可见。海马神经元脱失与脑损伤发生年龄呈正相关。结论:生命早期的脑损害是海马硬化的成因。硬化海马是难治性癫的致灶。以海马结构齿状回门区神经元,颗粒细胞和海马CA3锥体细胞脱失为特点的海马硬化是难治性颞叶癫的主要病理特点和病因,门区细胞的脱失是海马硬化的特征性病理改变,可能在难治性癫的发病机理中起着重要作用。     

Decrease in GABA immunoreactivity and alteration of GABA metabolism after kindling in the rat hippocampus

Summary The kindling model of epilepsy, induced by tetanic stimulation of Schaffer collateral/commissural fibers, was studied in the rat hippocampus. Gamma-aminobutyric acid immunoreactivity was used to quantify the number of GABA-immunoreactive somata per mm² in CA1 region, 28 days after the last generalized seizure. Comparison of the numbers obtained from kindled animals with those from controls, showed a significant decrease (18%) on the ipsilateral stimulated side but none on the contralateral side. In control rats injection of the GABA-transaminase inhibitor, amino oxyacetic acid (AOAA), led to a 46% increase in the number of cell somata immunoreactive for GABA. This probably results from an accumulation of GABA, reflecting GABA synthesis by glutamate decarboxylase (GAD) activity, in somata of interneurons that had initially a GABA content below the immunocytochemical detection threshold. In kindled rats, 31 days after the last seizure, the number of GABA-immunoreactive cells that could be observed after AOAA-treatment was significantly lower (35% ipsilateral and 25% contralateral) when compared to AOAA-treated controls. This suggests that in kindled animals a GAD dependent increase in GABA content did not take place in a subpopulation of interneurons. The observations for kindled rats are interpreted as a long-term decrease in GABA content and as an alteration in GABA turnover in a subpopulation of interneuron somata, the latter possibly due to a decrease in GAD activity. The long-term enhanced seizure sensitivity, characteristic for kindled animals, may be due to a decreased GABAergic inhibitory control of the neuronal circuitry in the CA1 region of the hippocampus.     

Region specific neuron loss in the aged canine hippocampus is reduced by enrichment

Neuron loss within the hippocampus and entorhinal cortex occurs as a function of age in humans. We first tested the hypothesis that neuron loss occurs in the aged dog. The total unilateral number of neurons in the canine entorhinal cortex and subdivisions of the hippocampus from the left hemisphere were estimated using the optical fractionator. The brains from 5 old (13.0-15.0 years old) and 5 young (3.4-4.5 years old) beagle dogs were analyzed. The hilus of the hippocampus showed a significant loss of neurons (approximately 30%) in the aged dog brain compared to young. Differences were not detected in the remaining hippocampal subfields and entorhinal cortex. We further tested the hypothesis that an antioxidant fortified food or behavioral enrichment would reduce the age-related loss of hilar neurons. Behaviorally enriched aged dogs had more neurons in the hilus (approximately 18%) compared to aged controls. These results suggest that the aged canine hippocampus in the left hemisphere shows selective neuron loss and that behavioral enrichment may reduce this loss.     

戊四氮癫痫幼鼠海马内NF-κB与N-Cadherin定位与苔藓纤维发芽现象

目的:探讨单次癫痫发作后脑内NF-κB和N-Cadherin表达与海马结构中苔藓纤维发芽现象之间的关系与作用。方法:利用腹腔注射戊四氮(PTZ)制作发育期SD大鼠(14 d、28 d)单次惊厥发作模型,各日龄组随机分为生理盐水(NS)组、PTZ组、吡咯二硫氨基甲酸酯(PDTC)组和PDTC+PTZ组,采用免疫组化法检测NF-κB和N-Cadherin的表达,利用Timm染色法观察海马苔藓纤维发芽现象。结果:NS组在海马CA3区可见极少Timm染色颗粒;致惊后1周偶见Timm染色颗粒、3周可见Timm染色颗粒沿海马CA3区呈条带样分布(P<0.01);PDTC预处理组Timm染色颗粒较PTZ致惊组明显减少(P<0.05)。NS组大鼠海马CA1、CA3区无NF-κB p65核转位细胞,致惊后24 h各日龄组幼鼠海马CA1、CA3区NF-κB p65核转位细胞较NS组明显增加(P<0.01);PDTC预处理后NF-κB p65的核转位细胞较致惊组明显减少(P<0.05)。NS组海马CA1、CA3区可见少量N-Cadherin阳性细胞;致惊组海马CA3和齿状回门区的N-Cadherin的阳性细胞与NS组相比明显增多(P<0.01),PDTC预处理后相同区域内N-Cadherin阳性细胞较PTZ致惊组明显减少(P<0.05)。NF-κB p65、N-Cadherin及Timm染色颗粒的表达结果与惊厥鼠的日龄并无关联性。结论:幼鼠单次惊厥发作可以引起海马不同程度的苔藓纤维发芽,而NF-κB p65、N-Cadherin的分布位置与变化时相与苔藓纤维发芽相吻合,表明NF-κB p65、N-Cadherin可能参与或伴随着苔藓纤维的发芽。     

c-Fos, N-methyl-d-aspartate receptor 2C, GABA-A-alpha1 immonoreactivity, seizure latency and neuronal injury following single or recurrent neonatal seizures in hippocampus of Wistar rat

To evaluate the long-term effects of single or recurrent prolonged neonatal seizures on seizure threshold and neuronal activity in the brain, a novel "twist" seizure was induced by coupling early-life flurothyl-induced seizures with later exposure to pentylenetetrazol. The authors assigned six neonatal rats for each group: the single-seizure group (SS), the recurrent-seizure group (RS) and the control group. At postnatal day 46, seizure threshold was examined using pentylenetetrazol, and then the brain slices were evaluated with thionine staining, in situ end labeling and immunohistochemical studies. The Results showed that the rats in SS and RS groups all had reduced latencies to develop generalized tonic seizures induced by PTZ compared with controls (P<0.01). Morphologic changes, cell loss and apoptotic cells were observed only in those of RS group. Significant fos and NR2C-immunoreactive positive cells were seen in hippocampus of rats in both SS and RS groups compared with controls (P<0.01). A significant decrease in the number of GABA-A-alpha1 immunoreactive positive neurons was detected in hippocampus in rats of SS and RS groups compared with the controls (P<0.01). We conclude that neonatal rats subjected to prolonged seizures have pronounced long-term effects on seizure threshold and neuronal neurophysiological activity in the brain. Obvious neuronal injury, however, was only seen in rat with recurrent-seizures. Subtle brain damage might occur in rats experiencing single prolonged neonatal seizures.     

Hippocampal neurons and glia in epileptic EL mice

Reactive changes in hippocampal astrocytes are frequently encountered in association with temporal lobe epilepsy in humans and with drug or kindling-induced seizures in animal models. These reactive changes generally involve increases in astrocyte size and number and often occur together with neuronal loss and synaptic rearrangements. In addition to producing astrocytic changes, seizure activity can also produce reactive changes in microglia, the resident macrophages of brain. In this study, we examined the effects of recurrent seizure activity on hippocampal neurons and glia in the epileptic EL mouse, a natural model of human multifactorial idiopathic epilepsy and complex partial seizures. Timm staining was used to evaluate infrapyramidal mossy fiber organization and the optical dissector method was used to count Nissl-stained neurons in hippocampus of adult (about one year of age) EL mice and nonepileptic C57BL/6J (B6) and DDY mice. Immunostaining forglial fibrillary acidic protein (GFAP) and Iba1, an actin cross-linking molecule restricted to macrophages and microglia, was used to evaluate astrocytes and microglia, respectively. The EL mice experienced about 25–30 complex partial seizures with secondary generalization during routine weekly cage changing. No significant differences were found among the mouse strains for Timm staining scores or for neuronal counts in the CA1 and CA3 pyramidal fields or in the hilus. However, the number of GFAP-positive astrocytes was significantly elevated in the stratum radiatum and hilus of EL mice, while microglia appeared hyper-ramified and were more intensely stained in EL mice than in the B6 or DDY mice in the hilus, parietal cortex, and pyriform cortex. The results indicate that recurrent seizure activity in EL mice is associated with abnormalities in hippocampal astrocytes and brain microglia, but is not associated with obvious neuronal loss or mossy fiber synaptic rearrangements. The EL mouse can be a useful model for evaluating neuron-glia interactions related to idiopathic epilepsy.     

BMP4参与海人酸损伤后成年大鼠海马齿状回颗粒细胞增殖及胶质增生

目的探讨海人酸（KA）侧脑室注射致大鼠海马损伤后骨形成蛋白-4（BMP4）的表达变化及其与颗粒细胞增殖和胶质细胞增生的关系。方法将成年大鼠分为对照组与实验组。侧脑室注射KA7d后,用尼氏染色检测海马神经元丢失,用免疫组织化学与原位杂交的方法检测海马齿状回BMP4mRNA阳性细胞与BrdU标记细胞、GFAP阳性细胞数的变化。结果正常成年大鼠BMP4mRNA阳性细胞主要分布于海马齿状回的门区、颗粒下层、CA3、CAI区。BrdU标记细胞主要分布在齿状回颗粒下层。GFAP阳性细胞主要分布在齿状回、CA3区。在KA侧脑室注射致海马损伤后7d,海马CA3、CA4区神经元丢失明显,BMP4mRNA阳性细胞与BrdU、GFAP阳性细胞均明显增加。结论KA侧脑室注射致海马损伤后,成年大鼠海马齿状回颗粒细胞增殖增强和胶质增生可能与BMP4表达增加有关。     

Pentylenetetrazole kindling induces neuronal cyclin B1 expression in rat hippocampus

The purpose of the study was to explore the involvement of cell cycle events in the neuronal death induced by repeated seizures. Pentylenetetrazole (PTZ) kindling was used as a model of seizure-induced hippocampal neurodegeneration. Immunohistochemical approach was applied to detect cell cycle markers (cyclins and cycline-dependent kinases) in hippocampus. PTZ-kindling in rats induced moderate neuronal cell loss in hippocampal fields CA1, CA 3, CA 4, and dentate gyrus. The majority of damaged cells in hippocampi of PTZ-kindled rats were cycline B1 positive, while no expression of either other cell cycle markers or TUNEL-positive (apoptotic) nuclei could be revealed. Since cycline B1 expression has been described in hippocampal neurons of patients with temporal lobe epilepsy by [Z. Nagy, M.M. Esiri, Neuronal cyclin expression in the hippocampus in temporal lobe epilepsy, Exp. Neurol. 150 (1998) 240-247], it is suggested that PTZ-kindling may be a suitable model to study the mechanisms of seizure-induced neuronal death.     

戊四氮致癫癎状态对大鼠长期行为和脑电的影响

目的：建立一种戊四氮（ＰＴＺ） 致癫癎状态（ＳＥ） 模型,并探讨ＰＴＺ 致惊厥与癫癎形成之间的关系。方法：观察ＰＴＺ 致抽搐发作（ 抽搐组） 和ＰＴＺ致抽搐延长发作即癫癎状态（ＳＥ 组） 对大鼠长期行为和脑电（ＥＥＧ） 的影响,同时观察二者是否产生海马、皮质神经元损伤。结果：ＰＴＺ 致抽搐延长发作能够产生具有某些癫癎特征的长期效应,如自发癎样放电、惊厥阈下剂量ＰＴＺ 可诱导癫癎发作以及皮质和海马神经元损伤,而单次抽搐发作不具有这些长期效应。结论：ＰＴＺ 致抽搐延长发作模型更符合ＳＥ 模型特点,惊厥持续时间与癫癎形成密切相关。     

Stereological cell counts of GABAergic neurons in rat dentate hilus following transient cerebral ischemia

We have previously demonstrated a 60-80% ischemic loss of somatostatinergic neurons in the dorsal dentate hilus of the rat. However, several studies have failed to demonstrate ischemic loss of GABAergic neurons in hilus, although one study reports that 96% of the somatostatinergic neurons in the dorsal hilus colocalize GABA. In order to understand this paradox, we have now estimated, using unbiased stereology, the total number of neurons immunohistochemically stained against glutamic acid decarboxylase-65 (GAD65) and GAD67 in the dorsal dentate hilus. Rats were divided into groups subjected to either sham operation (n=8) or 8 min of transient global ischemia during systemic hypotension (n=8) and allowed to survive for 7-9 days. Results from cell counts (mean +/- SD) in sham rats demonstrated that the dorsal hilus contains 9,189+/-3,957 GAD65 neurons and 6,991+/-2,784 GAD67 neurons. After ischemia, corresponding cell counts demonstrated 10,216+/-4,866 GAD65 neurons and 10,119+/-5,906 GAD67 neurons, and these results were not significantly different (P>0.05) from results in sham rats. Power analysis of the t-test informs that losses less than 80% are not significant and reflects the excessive variance in our material. For comparison, we estimated a total of 21% ischemic neuron death in the dorsal hilus on cresyl violet-stained sections from other corresponding sham (n=7) and ischemic rats (n=7). This explains why ischemic loss of hilar GABAergic neurons can only be detected by counts of the vulnerable subpopulation colocalizing somatostatin. Our investigation has demonstrated a surprisingly high variation between rats in a number of GAD-immunopositive neurons located in the dorsal dentate hilus, which is related to variations between the individual rats and neurons in their endogenous GAD expression.