Place cells recorded in the parasubiculum of freely moving rats

Previous studies have identified neurons in the hippocampus, subiculum, and entorhinal cortex which discharge as a function of the animal's location in the environment. In contrast, neurons in the postsubiculum and anterior thalamic nucleus discharge as a function of the animal's head direction in the horizontal plane, independent of its behavior and location in the environment. Because the parasubiculum (PaS) has extensive connections, either directly or indirectly, with these structures, it is centrally located to influence the neuronal activity in these areas. This study was therefore designed to determine the types of behavioral and spatial correlates in neurons from the PaS. Single unit recordings were conducted in the PaS of freely moving rats trained to retrieve food pellets thrown randomly into a cylindrical apparatus. A total of 10.3% of the cells were classified as place cells because they discharged in relation to the animal's location in the cylinder. A large percentage of cells (41.4%) were classified as theta cells. The remaining cells had nondiscernable behavioral correlates. Quantitative analysis of the firing rate maps for the place cells showed they had higher levels of background activity and contained larger firing fields than values reported previously for hippocampal place cells. Directional analysis showed that only three out of 16 cells contained a secondary directional correlate; the firing rate for the remaining cells was not affected by the animal's directional heading within the firing field. A time shift analysis, which shifted the spike time series relative to the animal location series, was conducted to determine whether the quality of the location-specific firing could be improved. The time shifts for three different spatial parameters were optimal when cell discharge led the animal's position. Furthermore, the optimal time shifts for two of these parameters (firing area and information content) were less than the optimal shift reported for hippocampal place cells and suggested that PaS cell discharge lagged behind hippocampal place cell activity. Rotation of the cue card with the animal out of view led to near equal rotation of the firing field when the animal was returned to the apparatus. These results indicate that a small population of cells in the PaS encode the animal's location in its environment, although the representation of space encoded by these cells is different from the type of representation encoded by hippocampal place cells. © 1995 Wiley-Liss, Inc.     

Place units in the hippocampus of the freely moving rat.

Single units were recorded from the CA1 field of the hippocampus in the freely-moving rat. They were classified as place units, displace units or others. Place units were defined as those for which the rat's position on the maze was a necessary condition for maximal unit firing. Some of these place units (misplace units) fired maximally when the animal sniffed in a place, either because it found something new there or failed to find something which was usually there. Displace units increased their rates during behaviors associated with theta activity in the hippocampal slow waves. In general these were behaviors which changed the rat's position relative to the environment. The influence of various environmental manipulations (e.g., turning off the room lights) on the firing pattern of the place units was tested and the results suggest that they were not responding to a simple sensory stimulus nor to a specific motor behavior. Nor could the unit firing be due purely to motivational or incentive factors. The results are interpreted as strong support for the cognitive map theory of hippocampal function.     

Deficits in parvalbumin and calbindin immunoreactive cells in the hippocampus of isolation reared rats

Summary Post-mortem studies have provided evidence for abnormalities of the γ-aminobutyric acid (GABA)-ergic system in schizophrenia. The calcium-binding proteins (CBPs), parvalbumin (PV), calbindin (CB) and calretinin (CR) can be used as markers for specific subpopulations of GABAergic neurons in the brain. Isolation rearing of rats is a non-pharmacological, non-lesion manipulation that leads to deficits in prepulse inhibition of the startle reflex (PPI) and other behavioural and neurochemical alterations reminiscent of schizophrenia. Female rats were reared in social housing (groups of three) or singly for 11 weeks post weaning and PPI was measured. Brains were removed and hippocampal CBP – containing neurons determined following immunocytochemical staining. Compared to socially housed rats, isolated rats exhibited PPI deficits and reductions in PV and CB-immunoreactive cells in the hippocampus, with no significant change in CR. These findings demonstrate selective abnormalities of sub-populations of GABAergic interneurons in the hippocampus of isolation reared rats, which resemble the neuronal deficits seen in this region in schizophrenia.     

脑卒中后抑郁大鼠海马原位增殖的新生细胞存活和分化状态

目的 观察脑卒中后抑郁(post-stroke depression,PSD)大鼠海马原位增殖新生细胞的存活和分化.方法 采用左侧大脑中动脉阻塞(MCAO)联合慢性不可预见温和应激刺激(chronicmild stress,CMS)及孤养法建立PSD模型,将雄性SD大鼠分为假手术、脑卒中、CMS和PSD组.每组均为18只.采取免疫组织化学、荧光双标染色及共聚焦成像动态检测,比较各研究组大鼠左侧海马齿状回溴脱氧尿苷嘧啶(BrdU)及其与神经元特异性核蛋白(NeuN)或胶质纤维酸性蛋白(GFAP)共表达.结果 与脑卒中组(232.2±8.6、123.7±2.6、136.2±2.6)相比,PSD组大鼠左侧(伤侧)海马齿状回BrdU+细胞数在脑梗死后第21(156.2±2.5)、30(70.2±2.0)和45天(81.2±1.1)均明显减少(t=28.83、52.2、62.08,均P<0.01),但仍高于假手术组.与脑卒中组(79.3%±2.8%、87.7%±4.6%)相比,PSD组大鼠左侧(伤侧)海马齿状回BrdU+/NeuN+细胞比例在脑梗死后第30(69.0%±3.4%)和45天(78.3%±2.4%)均明显减少(t=5.871、4.403,均P<0.01).BrdU+/GFAP+细胞比例在脑梗死后30和45 d均明显增加(t=4.226、8.945,P<0.01).结论 PSD大鼠脑卒中后海马齿状回原位增殖的新生细胞存活降低,分化为神经元的比例下降,胶质细胞比例增加.     

State-dependent columnar organization of dorsal hippocampal activity in the freely-behaving cat

We examined reflected light images from the dorsal hippocampus in freely-behaving cats to assess the topographical organization of neural activity expressed during sleep-waking states. Reflectance patterns, organized as columns along the CA3-CA1 axis which appeared during rapid eye movement sleep (REM) and waking states, were compared to baseline periods collected during quiet sleep (QS). The columns were not static across states or behaviors within a state, but showed inversion in activation/inactivation patterns, and narrowed or widened over time. A correlation between state-dependence and reflectance patterns emerged, with transitions to active waking and REM most likely exhibiting enhanced columnar patterning, relative to QS. No columnar patterns appeared in overlying neocortical areas or in control media. The columnar patterns suggest a highly structured functional state-dependent organization in the dorsal hippocampus, as has been previously predicted by anatomical studies.     

Morphology and migration of cultured schwann cells transplanted into the fimbria and hippocampus in adult rats

Schwann cells cultured from neonatal rat peripheral nerve were injected into the fimbria and hippocampus of syngeneic adult rats by a microtransplantation technique which causes minimal disturbance to the host brain structure at the site of implantation, and thus allows the grafted cells to come into immediate contact with intact host tissue. Numerous Schwann cells could be identified for up to 6 weeks (and with decreasing frequency for up to 3 months) by intense immunoreactivity for low affinity nerve growth factor receptor. The transplanted cells adopted a distinctive elongated form, with a central, ovoid nucleus flanked by processes which were up to 300 μm long, and which ranged from swollen segments with a diameter as large as 12 μm down to thread-like fibres of 1 μm or less. This morphology is different from that of any of the host cells. The transplanted Schwann cells migrated freely into the host tissue along blood vessels and according to the position of the grafts, they either entered the hippocampal neuropil, or migrated (for distances of up to 2 mm) along the longitudinal axis of the fimbria, where they were interspersed in parallel with the interfascicular glial rows and axons. The host astrocytes did not appear to impede the migration of the donor Schwann cells. Although the host astrocytic processes became hypertrophic, with increased glial fibrillary acidic protein and vimentin expression, the predominant longitudinal orientation of the astrocytic tract processes was maintained. The transplanted Schwann cells did not form peripheral myelin (as detected by P_o immunoreactivity), and it is not clear whether they survive beyond the period at which we detect them. © 1993 Wiley-Liss, Inc.     

柴胡总皂甙对戊四氮慢性点燃大鼠海马谷氨酸细胞的影响

目的研究柴胡总皂甙对戊四氮(PTZ)慢性点燃癫痫模型大鼠海马区谷氨酸(Glu)阳性细胞表达的影响。方法48只健康SD大鼠被随机分为6组,即空白组(A组)、生理盐水组(B组)、丙戊酸钠(VPA)组(C组)和柴胡总皂甙高、中、低三种剂量组(D组、E组、F组),每组8只,除A组不做处理外,其他各组采用腹腔注射PTZ慢性点燃造模,造模同时给予VPA、柴胡总皂甙等不同处理因素,连续4周后取脑组织切片进行Glu免疫组化染色,从阳性细胞数、灰度值分析结果。结果在CAl区,B组海马阳性细胞数高于A、C、D、E、F组,有显著性差异(P＜0．05),B组海马各区阳性细胞灰度值低于其他各组,与A、C、D各组比较,有显著性差异(P＜0．05)；而在CA2区和DG区,B组阳性细胞数、灰度值与各组差异无统计学意义。结论柴胡总皂甙可以影响PTZ点燃大鼠海马CA1区的Glu表达水平,从而抑制PTZ慢性点燃大鼠的痫性发作。     

Long-term survival of fetal porcine lateral ganglionic eminence cells in the hippocampus of rats.

Embryonic porcine brain tissue from the lateral ganglionic eminence was transplanted into the adult rat hippocampus to determine whether fetal striatal cells could survive, differentiate, and integrate in a heterotopic site. The hippocampus, a common site of epileptic seizure activity, was chosen to determine if fetal striatal cells could supply inhibitory GABAergic neurons that may serve to block seizures. Cells were either implanted with a single deposit using a standard metal cannula or by five smaller disseminated deposits with a glass micropipette. At 20-24 weeks, animals immunosuppressed with cyclosporin showed long-term survival of porcine cells in the adult hippocampus. Analysis by immunohistochemistry and in situ hybridization showed that the grafts contained glial and neuronal cell types, including GABAergic neurons within graft core and networks of porcine neuronal fibers extending from the graft into the host parenchyma. In addition, a marker of porcine presynaptic terminals, synaptobrevin, was abundant within the grafts and was found associated with hippocampal structures and cell layers suggesting functional integration of grafted cells within the host. The survival of xenografts in the hippocampus and potential integration of inhibitory components provides evidence that these grafts may serve as an internal negative feedback mechanism to quench epileptiform activity.     

RAGE is expressed in pyramidal cells of the hippocampus following moderate hypoxic-ischemic brain injury in rats

The receptor for advanced glycation end products (RAGE) is a multi-ligand member of the immunoglobulin superfamily of cell surface molecules. The RAGE-ligand interaction has a putative role in a range of chronic disorders and is also known to contribute to both inflammatory/degenerative processes as well as regeneration in peripheral nerve injury. We have investigated the expression of RAGE in the moderate hypoxic-ischemic (HI) rat brain injury model in order to determine if this receptor is involved in the cellular perturbation mediated by ischemic stress. RAGE mRNA levels were detected by in situ hybridization using a DIG-labelled 48 mer oligonucleotide probe. Results showed a high level of expression of RAGE mRNA in the CA1/2 pyramidal cell layer of the hippocampus on the lesioned side of the brain 72 h after a moderate hypoxic-ischemic insult. RAGE was not expressed on the control side of the hippocampus. The RAGE-positive cells had a unique morphology, being angular in shape and atrophied with a condensed cell nucleus. They were NeuN-positive and were identified as dying cells by staining with thionin/acid fuchsin. A subset of cells was positive for cleaved Caspase-3, a marker for apoptosis. Together these data show that RAGE is expressed in dying neurons and suggest that RAGE may have a role in neuronal cell death mediated by ischemic stress. Identification of the ligand for RAGE in the ischemic brain may lead to a better understanding of RAGE-mediated cellular dysfunction in the CNS.     

维甲酸诱导胚胎大鼠脑海马神经干细胞向神经元的分化

背景：目前认为直接进行神经干细胞移植后细胞虽能存活,但是只分化成神经胶质细胞,并不能分化成有功能的神经元。 目的：探讨维甲酸诱导对胚胎大鼠脑海马神经干细胞向神经元分化的作用。 设计、时间及地点：细胞学体外实验,于2008-09/2009-02在辽宁医学院科技实验楼完成。 材料：胚龄13.5 d的SD大鼠由辽宁医学院实验动物中心提供。 方法：分离胎鼠脑海马组织,胰蛋白酶消化法体外培养获得神经干细胞。将原代和传代细胞以1×107 L-1接种到培养孔中,分别进行常规贴壁分化培养和维甲酸诱导分化培养。 主要观察指标：神经干细胞的鉴定,光镜及免疫组化检测神经干细胞诱导分化结果。 结果：免疫组织化学检测结果显示,原代和传代后得到的神经干细胞团均呈巢蛋白阳性。常规贴壁分化培养7 d后,神经元多呈椭圆型和近似三角形,胞体大,细胞边缘清楚,胞体上有多个突起;而维甲酸诱导分化培养后,神经元数量增加,形态清楚,但细胞胞体上突起较少。与常规贴壁分化培养比较,维甲酸诱导分化培养后神经干细胞向神经元分化率明显升高(P < 0.01),神经干细胞向神经胶质细胞分化率明显降低(P < 0.01)。 结论：从大鼠胚胎脑海马组织中分离得到可自我复制和多向分化的神经干细胞,维甲酸体外诱导后可以增加其向神经元方向分化的比例。     

凋亡诱导因子在戊四氮致痫大鼠海马组织中的表达

目的研究凋亡诱导因子(AIF)mRNA在戊四氮(PTZ)点燃癫痫持续状态(SE)大鼠海马组织中的表达情况。方法通过腹腔注射戊四氮建立急性点燃大鼠模型,运用逆转录聚合酶链反应技术(RT-PCR)分析AIFmRNA在大鼠癫痫发作后的表达情况。结果癫痫发作后海马组织AIFmRNA的表达水平早期即出现升高(6h组与对照组相比,P<0.05),且持续较长一段时间(48h组与对照组相比,P<0.01)。结论AIF可能参与了戊四氮致痫大鼠海马神经元的凋亡过程。     

发育期大鼠海马氨基酸类神经递质的研究

目的用高效液相色谱法检测大鼠海马组织中氨基酸类神经递质,研究它们在发育期大鼠海马中含量的变化.方法采用安捷伦反相高效液相色谱柱(ZORBAX,XDB,C18,4.6mm×250mm,5μm,Agilent),异硫氰酸苯酯为柱前衍生剂,在柱温38℃下采用二元梯度洗脱,于254 nm波长处用VARIAN-Prostar 325紫外检测器和LC-WORKSTATION-V6.2色谱数据处理系统检测和处理对照品和大鼠海马样品的氨基酸色谱数据,并计算乳鼠、幼鼠和成鼠海马氨基酸含量.结果氨基酸含量在Asp0.036～0.586 mg/ml、Glu0.027～0.4336 mg/ml、Gly0.053～0.8438 mg/ml、Tau0.039～0.6312 mg/ml和GABA0.0268～0.4288 mg/ml时,其峰面积与氨基酸含量的线性相关系数均大于0.9995;五种氨基酸回收率在96.0%～106%之间.三组样品间五种氨基酸含量的差别均有极显著性意义(P<0.01).结论该法检测大鼠海马组织中氨基酸类神经递质灵敏,特异性好,且分析时间短.氨基酸类神经递质含量随大鼠海马的发育而增高.     

Domoic acid-induced neurotoxicity in the hippocampus of adult rats

Domoic acid (DA), an agonist of non-N-methyl-D-aspartate (non-NMDA) receptor subtype including kainate receptor, was identified as a potent neurotoxin showing involvement in neuropathological processes like neuronal degeneration and atrophy. In the past decade evidence indicating a role for excitatory amino acids in association with neurological disorders has been accumulating. Although the mechanisms underlying the neuronal damage induced by DA are not yet fully understood, many intracellular processes are thought to contribute towards DA-induced excitotoxic injury, acting in combination leading to cell death. In this review article, we report the leading hypotheses in the understanding of DA-induced neurotoxicity, which focus on the role of DA in neuropathological manifestations, the formation of the retrograde messenger molecule nitric oxide (NO) for the production of free radicals in the development of neuronal damage, the activation of glial cells (microglia and astrocytes) in response to DA-induced neuronal damage and the neuroprotective role of melatonin as a free radical scavenger or antioxidant in DA-induced neurotoxicity. The possible implications of molecular mechanism underlying the neurotoxicity in association with necrosis, apoptosis, nitric oxide synthases (nNOS and iNOS) and glutamate receptors (NMDAR1 and GluR2) related genes and their expression in DA-induced neuronal damage in the hippocampus have been discussed.     

Morphofunctional interrelationships between the hippocampus and hypothalamus in rats]

Evoked reactions of the hypothalamic arcuate and medial preoptic nuclei neurons were recorded when the hippocampus was stimulated by single stimuli in anaesthetized rats. In the arcuate nucleus phasic responses and primary inhibition were found to be dominant and in the medial preoptic nucleus--both phasic and nonspecifical responses. After injection of the horseradish peroxidase into the stimulated hippocampal region stained cells were found in the nuclei of the mammillary complex, mediobasal hypothalamus and in the medial preoptic nucleus. Groups of stained neurons were observed in the periphery of ventro- and dorsomedial, lateral and mammillary nuclei of the hypothalamus. In all the studied structures, except the medial mammillary nucleus, reticular-like cells were found alongside with spindle-like and triangle neurons. The data obtained are discussed in connection with the problem of hypothalamo-hippocampal interaction.     

Granulovacuolar degeneration in pyramidal cells of the hippocampus

Summary We have shown that as the number of granulovacuolar bodies in affected pyramidal cells of the hippocampus increases so cytoplasmic RNA contant is reduced. Prior to its degeneration, the nucleolus is increased in volume while that of the nucleus remains unchanged in size throughout. The effects of these degenerative changes are to bring about a progressive decline in the capacity for nerve cell function, leading evenually to the death of the cell.     

老年大鼠脑出血后海马齿状回神经干细胞的增殖与分化

目的 观察老年大鼠脑出血后海马齿状回神经干细胞(NSCs)的增殖与分化,探讨脑出血后NSCs的变化规律.方法 制作老年大鼠脑出血模型,5-溴脱氧尿核苷(BrdU)腹腔注射标记增殖细胞,用免疫组化法检测大鼠海马齿状回BrdU、神经元核抗原(NeuN)、胶质纤维酸性蛋白(GFAP)阳性细胞数的变化.结果 正常组和假手术组老年大鼠海马齿状回均有少量BrdU阳性细胞,脑出血后大鼠各时间段的BrdU阳性细胞数目均较正常组和假手术组明显增加,7d组达到峰值后逐渐下降,28d组仍高于正常组和假手术组.正常老年大鼠海马齿状回可见少量BrdU/NeuN和BrdU/GFAP双标阳性细胞,脑出血后双标阳性细胞数较正常组明显增加.结论 脑出血后老年大鼠海马齿状回NSCs增殖明显,且可以向神经元和神经胶质细胞分化.     

神经元型一氧化氮合酶在血管性痴呆大鼠海马中的表达

目的 探讨神经元型一氧化氮合酶(nNOS)在血管性痴呆(VD)大鼠海马中的表达。方法 将60只大鼠随机分为：对照组、VD12h组、VD1d组、VD3d组、VD7d组。采用反复夹闭双侧颈总动脉方法建立VD大鼠模型，用HE染色观察各组大鼠海马CA1区神经元的数目；应用免疫组化染色和Western印迹方法检测nNOS在大鼠海马中的表达。结果 VD12h组、VD1d组、VD3d组、VD7d组大鼠海马CA1区神经元数均明显下降。nNOS在对照组大鼠海马CA1区中弱表达．在VD12h组表达增强．VD1d组进一步增强，VD3d和7d组表达逐渐减弱。结论 nNOS可能参与缺血早期海马神经元的损害，是VD的发病机制之一。