NGF对新生大鼠隔神经元的神经营养作用

本实验观察了神经生长因子（ＮＧＦ，２．５ｓ）对无血清培养新生大鼠隔神经元生长发育的作用。结果证明，ＮＧＦ能促进新生大鼠隔神经元的存活，增加神经元胞体面积和直径，增加隔培养神经元中ＡＣｈＥ阳性神经元的数目。流式细胞分析显示，ＮＧＦ使神经元平均蛋白含量增加。以上结果表明：ＮＧＦ对新生大鼠隔神经元的生长发育具有促进作用。Ｐ＜０．０１３．ＮＧＦ增加隔培养神经元胞体面积、最长径和最短径图像分析结果可见：在前７ｄ，在神经元胞体面积、最长径和最短径等方面两组之间无明显差别，但在培养１４、２１和３０ｄ时，ＮＧＦ组培养神经元的平均胞体面积、最长径和最短径均大于对照组，经统计学处理有显著意义（表２）。表２对隔培养神经元胞体面积、最长径和最短径的影响（ｘ±ｓ）注：Ｎ＝３０与同时期对照组相比＊Ｐ＜０．０５Ｐ＜０．０１４．ＮＧＦ促进新生大鼠隔细胞的总量白合成用ＦＡＣＳ４４０流式细胞仪测定隔细胞的平均蛋白含量，结果表明：在培养３、７、１４和２１ｄ时，ＮＧＦ组培养细胞的平均蛋白含量均显著高于对照组（表３，Ｆｉｇ．１）。表３ＮＧＦ对隔神经元蛋白合成的影响（ｘ±ｓ）往：Ｎ＝５与同时期对照组相比　＊Ｐ＜０．０５５．ＮＧＦ提高隔神经元的ＡＣｈＥ?     

运动对小鼠海马结构和大脑皮质胆碱能纤维的影响

用组织化学方法结合体视学测量研究小鼠海马结构和大脑皮质胆碱能纤维的年龄变化以及长期适量运动（跑转笼）对胆碱能纤维的影响。以同年龄对照组心重／体重比率均值的２倍标准差作为运动有效标准。结果显示，老年鼠（２４月龄）海马ＣＡ１区、ＣＡ３区，齿状回分子层和运动、体感皮质第Ⅲ和Ⅴ层乙酰胆碱酯酶（ＡＣｈＥ）阳性纤维密度明显低于成年鼠（１３月龄）和青年鼠（５月龄）（Ｐ＜０．０１），后两者间除海马ＣＡ３区分子层纤维密度成年鼠稍低外Ｐ＜０．０５），其它各区无显著差异（Ｐ＞０．０５）；５月龄小鼠经过８和１９个月运动后，被检各区ＡＣｈＥ阳性纤维密度均显著高于同年龄对照组（Ｐ＜０．０１）。结果表明从青年开始的长期适量运动能够促进海马和皮质内胆碱能纤维的增生，延缓衰老时胆碱能纤维的丢失。     

大鼠中央杏仁核向迷走背核复合体的直接投射──HRP逆向追踪和形态计量学研究

依据细胞大小、形态和密度的不同，把中央杏仁核分为５个亚区：即内侧亚区（ＣＭ）、腹侧亚区（ＣＶ）、中间亚区（ＣＩ）、外侧亚区（ＣＬ）和外侧囊亚区（ＣＬＣ）。ＣＬ体积最大（０．１０３ｍｍ３），细胞总数最多（８７１１个），细胞中等大小，细胞密度最高（８．６４ｘ１０４个／ｍｍ３）；ＣＩ体积最小（０．０１６ｍｍ３）、细胞总数最少（１０７５个），但细胞最大；ＣＬＣ细胞密度最低（４．５４×１０４个／ｍｍ３），细胞也最小；ＣＭ和ＣＶ的各项参数介于上述最高和最低参数之间。将ＨＲＰ注入一侧迷走背核复合体的上部后，在同侧中央杏仁核各亚区内标记细胞的平均数及与其神经元总数的百分比为：ＣＭ：３７２１个，７０％；ＣＶ：１４１２个，３５％；ＣＩ：８３个，８％；ＣＬ：３９１个，５％。ＨＲＰ注射入闩下部后，数据为：ＣＭ：１８２２个，３４％；ＣＶ：６０６个，１５％；ＣＩ：６８个，６％；ＣＬ：２９５个，３％。本研究表明：向迷走背核复合体直接投射的神经元是中央杏仁核内较小的细胞。投射的主要亚区为ＣＭ和ＣＶ，两亚区向闩上部的纤维投射明显多于向闩下部的投射。     

Cholinergic medial septum neurons do not degenerate in aged 129/Sv control or p75(NGFR)-/-mice

Cholinergic medial septum neurons express TrkA and p75 nerve growth factor receptor (p75(NGFR)) and interactions between TrkA and p75(NGFR) are necessary for high-affinity binding and signaling of nerve growth factor (NGF) through TrkA. In adult p75(NGFR)-deficient (-/-) mice, retrograde transport of NGF and other neurotrophins by these neurons is greatly reduced, however, these neurons maintain their cholinergic phenotype and size. Reduced transport of NGF has been proposed to play a role in Alzheimer's disease. Here, we investigated whether chronic and long-term absence of p75(NGFR) (and possibly reduced NGF transport and TrkA binding) would affect the cholinergic septohippocampal system during aging in mice. In young (6-8 months), middle aged (12-18 months), and aged (19-23 months) 129/Sv control mice the total number of choline acetyltransferase-positive medial septum neurons and the mean diameter and cross sectional area of the cholinergic cell bodies were similar. The cholinergic hippocampal innervation, as measured by the density of acetylcholinesterase-positive fibers in the outer molecular layer of the dentate gyrus was also similar across all ages. These parameters also did not change during aging in p75(NGFR) -/- mice and the number and size of the choline acetyltransferase-positive neurons and the cholinergic innervation density were largely similar as in control mice at all ages. These results suggest that p75(NGFR) does not play a major role in the maintenance of the number or morphology of the cholinergic basal forebrain neurons during aging of these mice. Alternatively, p75(NGFR) -/- mice may have developed compensatory mechanisms in response to the absence of p75(NGFR).     

Human amnion membrane matrix as a substratum for axonal regeneration in the central nervous system

Summary Human Amnion Membrane Matrix (HAMM) was used as a substratum for the regeneration of neuronal axons in the central nervous system. A large piece of HAMM was bound to nitrocellulose paper (NCP) as a supporting material, and cut into small strips. Aspirative lesions of the fimbria-fornix were made in adult rats leaving a cavity separating the septum from the hippocampus. In the same operation a small piece of HAMM-NCP was placed into the cavity with one end abutting the axotomized septum and the other end abutting the denervated hippocampus. At times between 2 weeks and 3 months after surgery the brains of the animals were examined histologically for 1) host response to the implant; 2) maintenance of HAMM-NCP in the originally implanted orientation; 3) growth of acetylcholinesterase (AChE)-positive fibers on the HAMM; 4) growth of the AChE-positive fibers into the denervated hippocampus; and 5) non-neuronal cells on the HAMM. The NCP remained in place over the 3-month period. In most cases the HAMM and NCP remained apposed and caused no greater reaction in the brain beyond that created in response to the aspirative lesion alone. AChE-positive fibers grew out from the septum onto the HAMM by 2 weeks, and by 8 weeks more extensive growth was observed on the HAMM. By 8-weeks, AChE fibers could be clearly seen coming off the membrane and entering the host hippocampus. By double-labelling for the basement membrane side of the HAMM (using anti-human laminin antibodies) and for cholinergic fibers (using AChE histochemistry) in the same sections, it was possible to see fibers clearly growing on the laminin-positive side of the HAMM but little or no growth on the opposing laminin-negative stromal side. The most important variables for extensive growth appeared to be the accurate placement of the implant and the amount of time following the lesions. The placement of the matrix on NCP prior to implantation in the brain made it easier to orient the membrane between the septum and the hippocampus, and seemed to assist in maintaining the membrane in that orientation. The HAMM represents a useful, regeneration-promoting grafting material for central nervous system repair studies.     

The distribution of acetylcholinesterase(AChE)-positive nerves in chicken pancreas demonstrated by light and electron microscopy

The distribution of acetylcholinesterase (AChE)-positive nerve fibers in the chicken pancreas was investigated with histochemical methods at the light and electron microscopic level. AChE-positive nerve bundles were found to run along the pancreaticoduodenal artery and their branches proceed into interlobular connective tissue, form a plexus around the interlobular secretory ducts and small arteries, and penetrate the exocrine parenchyma. Intrapancreatic ganglia showing a strong AChE activity were detected within the interlobular connective tissue or between acini. The exocrine pancreas was richly innervated with AChE-positive terminals which contained a few large dense-cored vesicles (about 100 nm in diameter) and many small clear vesicles (about 50 nm in diameter). Such terminals made contact with intercalated ductular cells and the smooth muscles of larger blood vessels. The endocrine pancreas was supplied with fewer nerves than the exocrine pancreas. A different distribution of AChE-positive fibers was noticed between A- and B-islets which were distinguished immunohistochemically. B- and D-cells were richly innervated by AChE-positive nerves, whereas A-cells, only poorly. These observations make clear that the cholinergic system relates to the regulation of both exocrine and endocrine tissues, except A-cells, in the chicken pancreas.     

Impairment of the septal cholinergic neurons in MPTP-treated A30P α-synuclein mice

Dementia in Parkinson's disease (PDD) and dementia with Lewy bodies (DLB) are characterized by loss of acetylcholine (ACh) from cortical areas. Clinical studies report positive effects of acetylcholine esterase (AChE) inhibitors in PDD and dementia with Lewy bodies. We here report that the number of neurons expressing a cholinergic marker in the medial septum-diagonal band of Broca complex decreases in A30P α-synuclein-expressing mice during aging, paralleled by a lower AChE fiber density in the dentate gyrus and in the hippocampal CA1 field. After inducing dopamine depletion by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP), no acute but a delayed loss of cholinergic neurons and AChE-positive fibers was observed, which was attenuated by L-3,4-dihydroxyphenylalanine (DOPA) treatment. Expression of nerve growth factor (NGF) and tyrosine receptor kinase A (TrkA) genes was upregulated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride-treated wild type mice, but not in A30P α-synuclein expressing animals. In contrast, upregulation of sortilin and p75^NTR genes was found in the A30P α-synuclein-expressing mice. These results suggest that dopamine deficiency may contribute to the impairment of the septohippocampal system in patients with PDD and that L-3,4-dihydroxyphenylalanine may not only result in symptomatic treatment of the akinetic-rigid syndrome but may also alleviate the degeneration of basal forebrain cholinergic system and the cognitive decline.     

Nerve growth factor prevents cell death and induces hypertrophy of basal forebrain cholinergic neurons in rats withdrawn from prolonged ethanol intake

We have previously reported that the hippocampal cholinergic fiber network is severely damaged in animals withdrawn from ethanol, and that a remarkable recovery in fiber density occurs following hippocampal grafting, a finding that we suggested to be underpinned by the graft production of neurotrophic factors, which are known to be decreased after ethanol exposure. It is widely accepted that nerve growth factor (NGF) signals the neurons of the brain cholinergic system, including those of the medial septum/vertical limb of the diagonal band of Broca (MS/VDB) nuclei, from which the septohippocampal projection arises. Because neurons in these nuclei are vulnerable to ethanol consumption and withdrawal we thought of interest to investigate, in withdrawn rats previously submitted to a prolonged period of ethanol intake, the effects of intraventricular delivery of NGF upon the MS/VDB cholinergic neurons. Stereological methods were applied to estimate neuron numbers and neuronal volumes in choline acetyltransferase (ChAT)-immunostained and Nissl-stained material. We have found that in ethanol-fed rats there was a significant reduction in the total number of Nissl-stained and cholinergic neurons in the MS/VDB, and that the suppression of ethanol intake further decreased neuron numbers. In addition, the somatic size of ChAT-IR neurons was reduced by ethanol intake, and withdrawal further aggravated neuronal atrophy. NGF treatment prevented the withdrawal-associated loss, and induced hypertrophy, of cholinergic neurons.These findings show that exogenous NGF protects the phenotype and prevents the withdrawal-induced degeneration of cholinergic neurons in the MS/VDB. These effects might be due to the trophic action of NGF upon the basal forebrain cholinergic neurons, including the hippocampal fiber network that conveys this neurotrophin retrogradely to the MS/VDB, and/or upon their targets, that is, the hippocampal formation neurons.     

Ultrastructural localization of acetylcholinesterase in the guinea pig pineal gland

The ultrastructural localization of acetylcholinesterase (AChE) activity in guinea pig pineal gland was studied using the copper-glycine procedure. A small number of pinealocytes and bundles of unmyelinated nerve fibers were labeled by the AChE reaction. The AChE-positive pinealocytes were located near blood vessels and distributed in small groups. The AChE reaction product was localized in the perinuclear cistern, in the cisternae of the endoplasmic reticulum (ER), and in the saccules of the Golgi apparatus. These findings suggest that the AChE-positive pinealocytes synthesize AChE. The AChE reaction product was also seen in the intercellular space between pinealocyte processes. Besides pinealocytes, AChE activity was localized on the axolemma of myelinated and unmyelinated nerve fibers and in the basement membrane surrounding unmyelinated nerve fibers. Pseudocholinesterase activity was confined to Schwann cells, which showed the reaction product in their perinuclear cistern, in the cisternae of the ER, and on the plasmalemma.     

老年性学习记忆减退大鼠新皮质和海马结构胆碱能纤维的定量研究

用Ｍｏｒｒｉｓ水迷宫行为检测方法以青年组平均逃避潜伏期９５％和９９％正常值范围上限值为界将老年大鼠分为学习记忆正常组（老年正常组）和学习记忆减退组（老年减退组）,以Ｈｅｄｒｅｅｎ等推荐的ＡＣｈＥ组织化学染色方法结合形态计量方法对各组大鼠的额、枕、内嗅皮质、海马ＣＡ１区多形层、腔隙分子层和齿状回分子层外带的胆碱能纤维密度进行分析,结果显示老年减退组较老年正常组、青年组各层（除枕叶外）ＡＣｈＥ阳性纤维数量均明显减少（Ｐ０．０５,Ｐ＜０．０１）。老年正常组与青年组相比各层阳性纤维数量有所减少,但除海马ＣＡ１区腔隙分子层差异显著外,其余差异均无显著性。相关分析结果表明大鼠各层ＡＣｈＥ阳性纤维数量与其平均逃避潜伏期呈负相关关系,与原平台象限游泳距离占总距离百分比呈正相关关系。本研究提示老年性学习记忆能力减退与新皮质、海马结构胆碱能纤维溃变密切相关。     

神经生长因子促进老年鼠大脑皮质胆碱能纤维损伤后再生

目的：探讨神经生长因子（nerve growth factor,NGF)对老年鼠大脑皮质胆碱能神经纤维损伤后再生的影响。方法：老年SD大鼠顶皮质切一宽2mm的冠状切口,侧脑室注射NGF,AChE纤维染色结合体视系分析正常组,损伤对照组和NGF用药组切口嘴,尾侧区的胆碱能纤维的再生情况。结果：损伤对照组损伤1个月后,嘴侧AChE阳性纤维增生至正常111．44％,尾侧纤维减少至正常67．14％;NGF用药组嘴侧纤维密度比损伤对照组增多,为正常145．93％,尾侧纤维为正常127．95％,结论：提示NGF对老年乳类皮质胆碱能纤维后损伤再生具有一定促进作用。     

NGF treatment promotes development of basal forebrain tissue grafts in the anterior chamber of the eye

Summary The effects of nerve growth factor (NGF) on developing central cholinergic neurons were studied using intraocular grafts of rat fetal (E17) basal forebrain tissue. Prior to grafting, grafts were incubated in NGF or saline. Transplants were allowed to mature for six weeks, receiving weekly intraocular injections of NGF or saline. Measurements of NGF levels in oculo after one single injection showed that NGF slowly decreases in the anterior chamber fluid, and after one week, low but significant levels were still present in the eye. Following pretreatment with diisopropylfluorophosphate (DFP), the cholinergic neurons in the grafts were analyzed using three morphological markers: antibodies to cholineacetyltransferase (ChAT), antibodies to acetylcholinesterase (AChE Ab) and acetylcholinesterase histochemistry (AChE). The transplants grew well and became vascularized within the first week. The growth of the NGF-treated basal forebrain grafts was significantly enhanced as compared to the growth of the saline-treated grafts evaluated with repeated stereomicroscopical observations directly through the cornea of the etheranaesthetized hosts. The NGF-treated grafts contained almost twice as many cholinergic neurons seen with all the cholinergic markers used, as the salinetreated grafts. However, there was no difference in cholinergic cell density between the two groups. The morphology and size of an individual cholinergic neuron was similar in the two groups. The fiber density as evaluated with AChE-immunohistochemistry did not change after NGF-treatment. The DFP-treatment did not seem to affect the AChE-immunoreactivity since an extensive fiber network was found, whereas almost no fibers were seen using conventional AChE histochemistry. We have demonstrated that in oculo transplantation of basal forebrain is a useful model for examining in vivo effects of NGF on central cholinergic function. The marked volume increase of NGF-treated grafts and the unchanged density of cholinergic cells and terminals suggests, that NGF increases the survival of not only developing cholinergic neurons, but possibly other non-cholinergic neurons and non-neuronal cells as well. These results support the notion that NGF acts as a neurotrophic factor on cholinergic and possibly non-cholinergic cells in the central nervous system     

Basal forebrain cholinergic cell attachment and neurite outgrowth on organotypic slice cultures of hippocampal formation

Distributions of somata and neurites of cholinergic neurons were studied after seeding dissociated cells onto organotypic slice cultures. Slice cultures were made from hippocampal formation and adjacent cortical regions from rats or mice. Dissociated cell suspensions of basal forebrain tissue from rat or mouse fetuses were seeded onto the slice cultures. Combined cultures were maintained for 1-21 days in vitro. Cultures processed for acetylcholinesterase (AChE) histochemistry demonstrated non-random patterns of cholinergic cells and their neurites. Labeled cells appeared most frequently in the molecular layer of the dentate gyrus, and in the deeper layers of cortical regions adjacent to the hippocampus. Neurites extending from these labeled cells appeared to target the dentate molecular layer and the cortical subplate layer. By 4 days in vitro, AChE-positive basal forebrain cells display several short and thick neurites that appear to be dendrites, and one long process that appears to be an axon. By 5 days in vitro, dendrites are well developed; by 7 days the presumed axon has extended widely over the cortical target zone. These neurites are maintained through 3 weeks in culture. Distributions of cells varied with the age of the slice. AChE-labeled cells were not seen overlying hippocampal tissue when dissociated cells were seeded on slice cultures made from day 0 rats, but a few labeled cells were seen when seeded on slices from day 2 rats. Clear non-random patterns of labeled cells and neurite outgrowth were seen on slice cultures from day 5 or older pups. The non-random distribution seen with AChE-positive neurons was not seen using other techniques that labeled all cells (non-selective fluorescent labels) or all neurons; these techniques resulted in labeled cells scattered apparently homogenously across the slice culture.These studies demonstrate a non-random pattern of attachment or differentiation of basal forebrain cholinergic neurons when these cells are seeded onto cultured cortical slices; this pattern mimics the normal patterns of basal forebrain cholinergic projections to these cortical regions. These data suggest that the factors that normally guide basal forebrain-derived cholinergic axons to their target cells in vivo are present and detectable in this model system.     

Nerve growth factor-induced excitation of selected neurons in the brain which is blocked by a low-affinity receptor antibody

We have investigated the electrophysiological effects of nerve growth factor (NGF) on single-neuron activity in central nervous system (CNS) grafts of septum, spinal cord, and hippocampus in oculo. NGF was found to have slow-onset, long-lasting excitatory effects on the spontaneous firing of neurons in septal grafts, while no such effects were found in neurons of either hippocampal or spinal cord grafts. Pretreatment with an antibody against the p75 low-affinity NGF receptor blocked the NGF-induced excitations. A second NGF application caused much stronger excitatory responses in sensitive neurons. Our data suggest that forebrain cholinergic neurons may be selectively sensitive to NGF also at the neurophysiological level, responding by excitations, and that NGF upregulates these responses within less than an hour.     

Experimental studies on the acetylcholinesterase-positive nerves in the ovary of the rat

Adrenergic and acetylcholinesterase (AChE)-positive nerves were studied in the rat ovary four days after various experimental denervation procedures. Ablation of pelvic parasympathetic nerves (pelvic neurectomy [PN]) or abdominal vagotomy (AV) had no obvious affect on the adrenergic or AChE-positive nerves in the ovary. Section of the mesovarium resulted in the loss of all histochemically demonstrable adrenergic and AChE-positive nerves. Chemical sympathectomy with 6-hydroxydopamine (6-HD) resulted in the loss of all histo-chemically demonstrable adrenergic nerves. A few AChE-positive nerves remained in the hilar and medullary regions following chemical sympathectomy. When the presumptive parasympathectomy procedures (AV and PN) were combined with chemical sympathectomy, again no adrenergic nerves remained, however a few hilar and medullary AChE-positive fibers persisted after sympathec-tomy plus PN, but no AChE-positive fibers were demonstrable in the AV plus 6-HD group. These findings show that most of the AChE in ovarian nerves is localized in adrenergic nerves. It is suggested that the few AChE-positive fibers remaining in the ovarian hilar area after 6-HD treatment or 6-HD plus PN are derived from the vagus. These few AChE-positive nerves may be postganglionic vagal parasympathetic or they may be sensory fibers.     

Does the release of acetylcholine in septal slices originate from intrinsic cholinergic neurons bearing p75(NTR) receptors? A study using 192 IgG-saporin lesions in rats

In previous studies electrically-evoked release of acetylcholine in septal slices was demonstrated. The present experiment aimed at verifying if this release involved intrinsic neurons bearing p75(NTR) receptors. Long-Evans rats sustained injections of 192 IgG-saporin into the medial septum/diagonal band of Broca (0.8 microg). Sham-operated rats served as controls. Two to 3.5 weeks later, the electrically-evoked release of acetylcholine ([(3)H]ACh) was measured in slices from the lateral septum (LS), medial septum (MS) and diagonal band of Broca (DBB). Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity, and monoamine concentrations were measured in the septum, cortex and hippocampus. The lesion extent was also assessed by ChAT immunostaining in a separate series of rats. In the septum, the number of ChAT-positive neurons was depleted dramatically (>90% at the level of the injection site). In the hippocampus, the lesions reduced ChAT and AChE activity by 91% and 84%, respectively. In the cortex, this reduction was weaker (-55% and -47%). In the septal region, the reduction was either weak or not significant. The evoked release of acetylcholine in septal slices was not reduced, except in the slices from the LS (-64%). The effects of physostigmine and atropine confirmed the presence of autoreceptors. Our data exclude that a major part of the acetylcholine released by MS and DBB slices derived from intrinsic neurons bearing p75(NTR) receptors. In the LS, part of the released acetylcholine might be from projections of such neurons located in the LS, MS and/or DBB. These data also suggest that the MS and the DBB may be the target of extrinsic cholinergic innervation that does not bear p75(NTR) receptors.     

BDNF、NGF对体外培养的胚胆碱能神经元生长发育的影响

本文用AChE组化方法，研究了BDNF、NGF对培养的胚鼠基底前脑胆碱能神经元的作用及BDNF和NGF的协同作用。结果表明BDNF和NGF都具有增加AChE阳性神经元数量的作用，二者的不同在于BDNF作用出现的时间较早、强度较小；而NGF作用出现的时间较迟但强度较大。并发现BDNF对体外培养的胚胆碱能神经元胞体早期的生长发育作用比较明显，而NGF的作用则不甚显著。BDNF对胚胆碱能神经元发出突起和突起的延伸作用较NGF强。BDNF和NGF的联合作用较单独使用BDNF或NGF为好。本文的结果提示在体外培养中两种营养因子联合应用较只用一种因子有益。     

Urea enhances the nerve growth factor-induced neuroprotective effect on cholinergic neurons in organotypic rat brain slices

Cholinergic neurons degenerate in Alzheimer's disease and dementia and neuroprotective substances are of high interest to counteract this cell death. The aim of the present study was to test the effect of urea and the nitric oxide synthetase inhibitor l-thiocitrulline on the survival of cholinergic neurons. Organotypic brain slices of the basal nucleus of Meynert were cultured for 2 weeks in the presence of 1-100 microM urea with or without NGF or other growth factors or with or without 1-10 microM of the NOS inhibitor L-thiocitrulline. A high number of cholinergic neurons survived in the presence of 0.1-100 ng/ml NGF. Urea or L-thiocitrulline alone did not exhibit neuroprotective activity; however, when brain slices were incubated with urea or L-thiocitrulline together with NGF there was a significant potentiating survival effect. Incubation of brain slices with NGF + urea + L-thiocitrulline did not further enhance the number of cholinergic neurons. NGF as well as urea did not stimulate expression of the enzyme choline acetyltransferase pointing to survival promoting effects. Urea did not modulate the NGF binding in PC12 cells indicating that this effect was indirect. It is concluded that urea may play a role as an indirect survival promoting molecule possibly involving the nitric oxide pathway.     

Acetylcholinesterase activity of primary sensory neurons and dorsal root fibers in the cat

Dorsal roots and spinal ganglion cells of adult cats were studied for acetylcholinesterase (AChE) content. An inverse correlation exists between cell size and AChE activity; large neurons are AChE-negative whereas small ones are intensely AChE-positive. A few AChE-positive fibers were demonstrated in the dorsal roots. A possible correlation between AChE activity and substance P content of primary sensory neurons is discussed.     

Neurotrophic effect of brain-derived neurotrophic factor on basal forebrain cholinergic neurons in culture from postnatal rats.

We examined the effect of brain-derived neurotrophic factor (BDNF) on cholinergic neurons in culture from postnatal rat basal forebrain by assay of choline acetyltransferase (ChAT) activity and cytochemical staining for acetylcholinesterase (AChE). BDNF was found to increase the ChAT activities but failed to promote the survival of AChE-positive neurons in cultures from neonatal (P3) rats, suggesting that its main role is cholinergic differentiation. In contrast, an enhancement of the survival of AChE-positive neurons and of ChAT activity was observed in cultures from P15-16 rats, suggesting that BDNF's main action is the maintenance of cholinergic neurons. Our results indicate a similarity between BDNF and nerve growth factor effects on the responses of cholinergic neurons of postnatal rat basal forebrain in culture.