胚基底前脑和胚大脑皮质植入老年性痴呆模型鼠大脑皮质的研究

本文取15～17天胚龄的SD大鼠胚基底前脑和胚大脑皮质分别制成悬液植入老年性痴呆同种模型鼠的大脑额、顶叶皮质,存活10个月后进行主动和被动迷宫学习和记忆行为的测试以及组织学检查。结果表明移植入的胆碱能神经元在模型鼠脑中发挥功效,为脑移植治疗老年性痴呆提供一定的实验和理论依据。     

BDNF和神经干细胞联用对穹隆海马伞切割鼠基底前脑p75NGFR阳性神经元数及其形态学的影响

目的研究神经干细胞（NSC）和脑源性神经营养因子（BDNF）联合治疗对穹隆海马伞切割鼠基底前脑p75^NGFR阳性神经元厦其形态学的影响。方法切断SD大鼠左侧穹隆海马伞模拟AD大鼠模型，利用无血清培养技术获得新生SD鼠的海马NSC。基底前脑注射NSC，同时侧脑室注射BDNF,4周后行免疫组化结合图象分析技术观察各组大鼠基底前脑p75^NGFR阳性神经元厦其形态学变化。结果损伤组大鼠p75^NGFR阳性神经元数在内侧隔核（MS）和斜角带（VDB）较正常组明显下降（P〈0．01）；移植组细胞数较损伤组有改善（P〈0．05）；与正常组相比较，联合组免疫阳性神经元数无显著下降（P〉0．05）。形态学参数测试结果显示，p75^NGFR阳性神经元的面积、周长在4组中的改变类似p75^NGFR阳性神经元数。结论NSC和BDNF联用较单独使用BDNF或NSC更好地增加p75^NGFR阳性神经元数及其形态学参数。     

神经干细胞移植对192-IgG-saporin阿尔茨海默病模型鼠基底前脑神经元p75NGFR阳性神经元和行为学的影响

神经干细胞能够在体外持续扩增,具有较强的增殖能力和较强的可塑性,能够在成年宿主中枢神经系统中存活、迁移、分化以及与宿主组织整合较好。 目的：分析神经干细胞移植对侧脑室注射192-IgG-saporin 老年性阿尔茨海默病模型鼠基底前脑神经元p75NGFR阳性神经元和行为学的影响。 方法：24只SD大鼠随机数字表法均分为3组：对照组、模型组、移植组。10只新生SD鼠(<24 h)用于神经干细胞分离培养。模型组及移植组192-IgG-saporin侧脑室注射SD大鼠建立阿尔茨海默病模型。造模后,移植组行基底前脑神经干细胞移植。4周后行Y迷宫检测,结合图像分析技术观察大鼠基底前脑p75NGFR阳性神经元数目和形态学参数的变化。 结果与结论：注射192-IgG-saporin 1个月,模型组损伤侧基底前脑内侧隔核和斜角带垂直支p75NGFR阳性神经元数明显减少(P < 0.01),移植组分别恢复到对照组的74.85%和71.66%,与模型组损伤侧相比较,差异显著(P < 0.01)。Y迷宫测试结果显示,移植组大鼠的空间学习能力和记忆能力有改善(P < 0.05),基底前脑p75NGFR阳性神经元细胞数与大鼠的空间学习记忆能力呈正相关。提示,神经干细胞移植对注射192-IgG-saporin致阿尔茨海默病鼠基底前脑胆碱能神经元有明显的补充和保护作用,可改善大鼠的学习记忆能力。     

神经生长因子在老年痴呆动物模型中的作用

将老年大白鼠(24个月)左侧海马繖部分切断,建立基底前脑胆碱能损害的老年痴呆动物模型。予侧脑室注射神经生长因子(NGF),分别在用药后15天和30天测隔区和海马胆碱乙酰转移酶(ChAT)活性。以正常鼠组和细胞色素C注射组作为对照。损害后隔区和同侧海马ChAT活性显著减少;NGF15天治疗组,隔区和损害对侧海马酶活性显著增加,是正常组的130％;30天治疗组,同侧海马酶活性比细胞色素C组增加48％。结果表时,NGF对老年鼠基底前脑胆碱能系统损害的治疗是有效的。本文还讨论了NGF在损害后急、慢性期的作用机制。     

神经干细胞移植对AD鼠基底前脑NOS阳性神经元的影响

目的 探讨神经干细胞（neural stem cells,NSCs）移植对老年性痴呆鼠基底前脑一氧化氮合酶（NOS）阳性神经元的影响.方法 切断成年SD大鼠左侧穹窿海马伞（fimbria-fornix,FF）,于基底前脑行神经干细胞移植,4周后行组织化学染色结合图像分析技术观察各组大鼠基底前脑NOS阳性神经元数量和形态学参数的变化. 结果 损伤后大约1个月,损伤侧基底前脑内侧隔核（MS）和斜角带垂直支（VDB）内可观察到NOS阳性神经元明显减少,分别为正常组的35.5%和55.8%,（与正常组相比P＜0.01）;移植组NOS阳性神经元数恢复到正常组的74.7%和95.7%,（与损伤组相比P＜0.01）.细胞形态学参数提示移植组NOS阳性神经元中含部分中等大小的未成熟细胞.结论 神经干细胞移植治疗,对AD模型鼠基底前脑MS、VDB的NOS阳性神经元有明显的补充和保护作用。     

阿尔茨海默病中神经生长因子及其受体的变化

阿尔茨海默病(Alzheimer’s disease,AD)又称老年性痴呆,是一种原因未明以记忆力下降和认知功能减退为主要临床表现的神经系统退行性疾病。神经生长因子(NGF)是最早发现且在脑内广泛分布的神经营养因子类物质。研究发现阿尔茨海默病中靶脑区NGF受体TrkA表达减少导致NGF逆向运输减少,以致Meynert基底核NGF减少,从而使基底前脑胆碱能神经元缺乏足够的NGF供应,促使基底前脑胆碱能神经元退变。有关动物实验研究表明神经生长因子能够在一定程度上缓解神经元变性。     

BDNF,NT-3对体外培养的胚鼠脊髓AChE和NADPH-d阳性神经元生长发育的影响

利用AChE和NADPH-d酶组织化学染色法研究了脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)和神经营养因子-3(neurotrophin-3,NT-3)对离体培养的胚胎大鼠脊髓胆碱能神经元和一氧化氮能神经元生长发育的影响.结果显示:BDNF处理组和NT-3处理组AChE阳性神经元数和NADPH-d阳性神经元数均显著高于对照组(P＜0.05).BDNF组AChE阳性神经元和NADPH-d阳性神经元胞体平均直径、每细胞突起数和最长突起长度均显著高于对照组(P＜0.05).NT-3组NADPH-d阳性神经元的生长发育与对照组无明显差异,仅AChE阳性神经元的每细胞突起数和最长突起长度显著高于对照组(P＜0.05),对胞体发育无影响.结果提示:BDNF,NT-3促进脊髓神经元的存活和生长发育,二者的作用具有选择性和特异性.     

Meynert核注射β-淀粉样蛋白后大鼠脑NGF、BDNF神经元的表达变化及其机制

目的:探讨Meynert核注射β-淀粉样蛋白(Aβ)后大鼠脑神经生长因子(nerve growth factor，NGF)和脑源性神经营养因子(brain derived neurotropic factor，BDNF)免疫反应性神经元的表达变化及其可能机制。方法将1μL Aβ1-40(10μg／μL)在立体定向仪下注入大鼠右侧Meynert核，分别于1、4周时测定其学习记忆能力和脑组织中NGF、BDNF免疫反应阳性神经元的表达。结果：Aβ1-40注射1周后，实验组出现学习记忆障碍，呈渐进性加重，4周时更为显著。在Meynert核及其周边、海马区和额、顶部皮层区，对照组有少量NGF、BDNF免疫反应阳性神经元分布，染色较浅；而实验组在1周时，较对照组无明显变化，4周时实验组NGF、BDNF免疫反应阳性神经元表达数量显著增加，以海马区最为显著，皮层区次之。结论：皮层和海马至基底前脑神经元的NGF、BDNF运输障碍，使基底前脑的神经元缺乏神经营养，致神经元变性及死亡，可能是阿尔茨海默病(Alzlaeimer disease，AD)学习记忆障碍和痴呆形成的重要因素之一。     

BDNF，NT—3对体外培养的胚鼠脊髓AChE和NADPH—d阳性神经元生长发育的影响

利用AChE和NADPH d酶组织化学染色法研究了脑源性神经营养因子 (brain derivedneurotrophicfac tor ,BDNF)和神经营养因子 3(neurotrophin 3,NT 3)对离体培养的胚胎大鼠脊髓胆碱能神经元和一氧化氮能神经元生长发育的影响。结果显示 :BDNF处理组和NT 3处理组AChE阳性神经元数和NADPH d阳性神经元数均显著高于对照组 (P <0 .0 5 )。BDNF组AChE阳性神经元和NADPH d阳性神经元胞体平均直径、每细胞突起数和最长突起长度均显著高于对照组 (P <0 .0 5 )。NT 3组NADPH d阳性神经元的生长发育与对照组无明显差异 ,仅AChE阳性神经元的每细胞突起数和最长突起长度显著高于对照组 (P <0 .0 5 ) ,对胞体发育无影响。结果提示 :BDNF ,NT 3促进脊髓神经元的存活和生长发育 ,二者的作用具有选择性和特异性。     

β-淀粉蛋白脑室内注射建立阿尔茨海默病大鼠模型

目的　观察β淀粉样蛋白(Aβ)脑室内注射建立阿尔茨海默病(AD)大鼠模型及其对大鼠行为、胆碱乙酰转移酶(ChAT)活性、细胞凋亡、神经生长因子(NGF)水平等影响。方法　将Aβ1 -42注射入大鼠侧脑室,于第1周、2周、4周观察Morris水迷宫逃避潜伏期、测定脑内ChAT活性、进行原位末端标记凋亡染色及NGF免疫组化染色。结果　Aβ1- 42注射后第2周大鼠Morris水迷宫逃避潜伏期延长,4周时更明显。2周后海马、皮层ChAT活性下降,4周后脑内ChAT活性广泛下降,以海马最为显著。2周后基底前脑Meynert核区凋亡细胞较其他脑区增多,NGF阳性细胞明显减少。结论　Aβ脑室内注射可以模拟AD行为改变,使脑内ChAT活性降低,基底前脑NGF含量减少,胆碱能神经元凋亡,可以作为AD研究模型。     

Cerebrolysin modulates pronerve growth factor/nerve growth factor ratio and ameliorates the cholinergic deficit in a transgenic model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by degeneration of neocortex, limbic system, and basal forebrain, accompanied by accumulation of amyloid‐β and tangle formation. Cerebrolysin (CBL), a peptide mixture with neurotrophic‐like effects, is reported to improve cognition and activities of daily living in patients with AD. Likewise, CBL reduces synaptic and behavioral deficits in transgenic (tg) mice overexpressing the human amyloid precursor protein (hAPP). The neuroprotective effects of CBL may involve multiple mechanisms, including signaling regulation, control of APP metabolism, and expression of neurotrophic factors. We investigate the effects of CBL in the hAPP tg model of AD on levels of neurotrophic factors, including pro‐nerve growth factor (NGF), NGF, brain‐derived neurotrophic factor (BDNF), neurotropin (NT)‐3, NT4, and ciliary neurotrophic factor (CNTF). Immunoblot analysis demonstrated that levels of pro‐NGF were increased in saline‐treated hAPP tg mice. In contrast, CBL‐treated hAPP tg mice showed levels of pro‐NGF comparable to control and increased levels of mature NGF. Consistently with these results, immunohistochemical analysis demonstrated increased NGF immunoreactivity in the hippocampus of CBL‐treated hAPP tg mice. Protein levels of other neurotrophic factors, including BDNF, NT3, NT4, and CNTF, were unchanged. mRNA levels of NGF and other neurotrophins were also unchanged. Analysis of neurotrophin receptors showed preservation of the levels of TrKA and p75^NTR immunoreactivity per cell in the nucleus basalis. Cholinergic cells in the nucleus basalis were reduced in the saline‐treated hAPP tg mice, and treatment with CBL reduced these cholinergic deficits. These results suggest that the neurotrophic effects of CBL might involve modulation of the pro‐NGF/NGF balance and a concomitant protection of cholinergic neurons. © 2012 Wiley Periodicals, Inc.     

Region-specific neurotrophin imbalances in Alzheimer disease: decreased levels of brain-derived neurotrophic factor and increased levels of nerve growth factor in hippocampus and cortical areas

BACKGROUND: Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and neurotrophin 4/5 (NT-4/5) are members of the neurotrophin gene family that support the survival of specific neuronal populations, including those that are affected by neurodegeneration in Alzheimer disease (AD). OBJECTIVE: To determine whether neurotrophin protein levels are altered in the AD-affected brain compared with control brains. METHODS: We quantitated protein levels of NGF, BDNF, NT-3, and NT-4/5, and calculated neurotrophin/NT-3 ratios in AD-affected postmortem hippocampus, frontal and parietal cortex, and cerebellum, and compared them with age-matched control tissue (patients with AD/controls: hippocampus, 9/9 cases; frontal cortex, 19/9; parietal cortex, 8/5; and cerebellum, 5/7, respectively). We applied highly sensitive and specific enzyme-linked immunosorbent assays in rapid-autopsy-derived brain tissue (mean+/-SD postmortem interval, 2. 57+/-1.75 h, n=71) to minimize postmortem proteolytic activity. RESULTS: Levels of BDNF were significantly reduced in hippocampus and parietal cortex (P<.001, and P<.01) as well as BDNF/NT-3 ratios in frontal and parietal cortices (P<.05, and P<.01) in the group with AD compared with the control group. Levels of NGF and NGF/NT-3 ratio were significantly elevated in the group with AD compared with the control group in the hippocampus and frontal cortex (P<.001). Levels of NT-4/5 and the NT-4/NT-3 ratio were slightly reduced in hippocampus and cerebellum in the group with AD compared with the control group (P<.05). In contrast, the levels of NT-3 were unchanged in all brain regions investigated. CONCLUSION: Decreased levels of BDNF may constitute a lack of trophic support and, thus, may contribute to the degeneration of specific neuronal populations in the AD-affected brain, including the basal forebrain cholinergic system. Arch Neurol. 2000.     

Brain-derived neurotrophic factor administration protects basal forebrain cholinergic but not nigral dopaminergic neurons from degenerative changes after axotomy in the adult rat brain.

Cell culture studies with dissociated primary cultures from embryonic rat brain revealed that brain-derived neurotrophic factor (BDNF) promotes the developmental differentiation of both basal forebrain cholinergic and mesencephalic dopaminergic neurons. These studies suggested that, in the adult brain, BDNF may be able to protect cholinergic and dopaminergic neurons from degenerative changes induced by axotomy, similar to the known protective action of NGF in cholinergic neurons. Testing this hypothesis, we found that intraventricular administration of recombinant human BDNF (rhBDNF) to adult rats with transections of the fimbria significantly reduces axotomy-induced degenerative changes of the cholinergic cells in the basal forebrain. No such effect was seen on the dopaminergic neurons of the ventral mesencephalon after transection of their axons ascending in the medial forebrain bundle. Injected in equal amounts, rhBDNF and recombinant human NGF had quantitatively different effects on the cholinergic neurons. BDNF sustained only part of the population of cholinergic neurons affected by the lesion, whereas the entire population was protected by NGF treatment.     

Synergistic Trophic Actions on Rat Basal Forebrain Neurons Revealed by a Synthetic NGF/BDNF Chimaeric Molecule

Basal forebrain cholinergic neurons, which degenerate in Alzheimer's disease, respond to multiple trophic factors, including the neurotrophins, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). This dual responsiveness prompted us to investigate the effects of a synthetic chimaeric molecule, containing the active domains of both NGF and BDNF. The NGF/BDNF chimaeric factor exhibited synergistic actions, and was 100-fold more potent than wild-type BDNF in enhancing survival of cultured dissociated basal forebrain cholinergic neurons. This effect was apparently due to true BDNF/NGF synergy, since addition of the two wild-type trophins simultaneously reproduced the effect of the chimaera. Synergy was selective for neurons which respond to both factors; substantia nigra dopaminergic neurons, which respond to BDNF but not NGF, exhibited no potentiation. The chimaeric factor thus revealed a synergy that may normally occur in the brain, and constitutes a potentially novel therapeutic agent with greater potency than naturally occurring individual trophins.     

Highly selective effects of nerve growth factor,brain-derived neurotrophic factor,and neurotrophin-3 on intact and injured basal forebrain magnocellular neurons

Cholinergic neurons of the basal nucleus complex (BNC) respond to nerve growth factor (NCF), the first member of a polypeptide gene family that also includes brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5), NGF, BDNF, and NT-3 are enriched in hippocampus. In addition, NGF and, more recently, BDNF have been shown to stimulate the cholinergic differentiation and enhance the survival of BNC cells in vitro. The present investigation was designed to test, in a comparative fashion, the in vivo effects of human recombinant NGF, BDNF, and NT-3 with confirmed activities in vitro on cholinergic and γ-aminobutyric acid (GABA)-ergic BNC neurons. The specific questions asked were whether and, to what extent, biologically active recombinant neurotrophins stimulate the transmitter phenotypes of intact cholinergic and GABAergic neurons of the BNC, and whether, and to what extent, recombinant neurotrophins protect the transmitter phenotypes of axotomized cholinergic and GABAergic neurons of the BNC following complete transections of the fimbria-fornix (measured by ChAT mRNA hybridization). Our results confirm the profound stimulatory and p^75NGFR expression in both intact and axotomized cholinergic neurons and to exert minor effects on some cholinergic markers (e.g., ChAT immunoreactivity). NT-3 had no influence on GABAergic neurons. Taken together, these results indicate that, despite their significant sequence homologies and their shared abundance in target fields of BNC neurons, NGF, BDNF, and NT-3 show striking differences in their efficacies as cholinergic trophic factors. GABAergic neurons of the BNC are resistant to neurotrophins. The result of the present investigation establish that NGF excels among neurotrophins as a trophic factor for intact and injured basal forebrain cholinergic neurons. © 1994 Wiley-Liss, Inc.     

Loss of Developing Cholinergic Basal Forebrain Neurons Following Excitotoxic Lesions of the Hippocampus: Rescue by Neurotrophins

Previous studies have demonstrated that the viability of developing cholinergic basal forebrain neurons is dependent upon the integrity of neurotrophin-secreting target cells. In the present study, we examined whether infusions of nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) could prevent the loss of cholinergic septal/diagonal band neurons following excitotoxic lesions of their target neurons within the hippocampus. Postnatal Day 10 rat pups received unilateral intrahippocampal injections of ibotenic acid. Rats then received intracerebroventricular (icv) injections of nerve growth factor (30 μg/injection), brain-derived neurotrophic factor (60 μg/injection), or saline immediately following the lesion and continuing every third day for 27 days. Both saline- and BDNF-treated rats displayed a significant loss of septal/diagonal band neurons expressing the protein and mRNA for choline acetyltransferase (ChAT) and p75 low-affinity nerve growth factor receptor ipsilateral to the lesion. The magnitude of this loss was significantly attenuated in BDNF-treated rats. Many remaining neurons were atrophic with stunted dendritic processes. In contrast, NGF treatment completely rescued these cells and prevented the shrinkage of remaining cholinergic septal neurons. In addition, both NGF and BDNF induced a sprouting of cholinergic processes within the residual hippocampal remnant ipsilateral to the infusions. The present study demonstrates that icv injections of NGF, and to a lesser extent BDNF, prevent the loss of developing basal forebrain neurons which occurs following removal of normal target cells. Diffusion studies revealed relatively poor penetration of BDNF into brain parenchyma. Thus, it remains to be determined whether the failure of BDNF to provide optimal trophic support for these cells is biological or due to restricted bioavailability of this trophic factor.     

Cultured basal forebrain cholinergic neurons from postnatal rats show both overlapping and non-overlapping responses to the neurotrophins

Basal forebrain cholinergic neurons respond in vitro and in vivo to nerve growth factor (NGF) and to brain-derived neurotrophic factor (BDNF). It is not clear to what extent the neurons that respond to these two factors, or to neurotrophin-3 or−45 (NT-3;NT-45) are identical or only partially overlapping populations. We have addressed this issue in cultures of basal forebrain neurons derived from 2-week-old postnatal rats, using choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) as cholinergic markers. Cholinergic neuron survival was enhanced in the presence of NGF, BDNF andNT-45.NT-45 was as effective as BDNF. NT-3 was without effect at this age, although in cultures derived from embryonic forebrain, cholinergic differentiation was induced by NT-3. Cotreatment with NGF and BDNF resulted in small, but consistent, increases in the number of ChAT-positive neurons, compared with either factor alone.NT-45 was also found to be additive with NGF, whereas cotreatment with BDNF andNT-45 showed no addivity. NT-3 had no additive effects with any other neurotrophin on any cholinergic parameters in postnatal cultures. Taken together, the results indicate the existence in postnatal rat brain of a large overlapping population of cholinergic neurons that are responsive to ligands for the neurotrophin receptors TrkA (NGF) and TrkB (BDNF andNT-45), but not TrkC (NT-3), and small distinct populations that show specificity for NGF or BDNF but not both. We hypothesize that cholinergic neurons projecting into different regions of the hippocampus may derive trophic support from distinct neurotrophins.     

Serum brain-derived neurotrophic factor, nerve growth factor and neurotrophin-3 levels in dementia

The aim of this study is to measure serum levels of neurotropic factor (NF) in patients with dementia. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) were determined in Alzheimer's dementia patients without medication (AD; n: 22), Alzheimer's dementia patients receiving cholinesterase inhibitor (CEI) treatment (AD?+?CEI; n: 32) and vascular dementia patients receiving CEI treatment (VaD?+?CEI; n: 27) and the age-matched control group (n: 20). NGF levels were detected to be significantly higher in the control group than in AD group (P?相似文献   

Positive Feedback between Acetylcholine and the Neurotrophins Nerve Growth Factor and Brain-derived Neurotrophic Factor in the Rat Hippocampus

In the rat hippocampus, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are synthesized by neurons in an activity-dependent manner. Glutamate receptor activation increases whereas GABAergic stimulation decreases NGF and BDNF mRNA levels. Here we demonstrate that NGF and BDNF mRNA and NGF protein are up-regulated in the rat hippocampus by the activation of muscarinic receptors. Conversely, NGF and BDNF enhance the release of acetylcholine (ACh) from rat hippocampal synaptosomes containing the nerve endings of the septal cholinergic neurons. NGF also rapidly increases the high-affinity choline transport into synaptosomes. The reciprocal regulation of ACh, NGF and BDNF in the hippocampus suggests a novel molecular framework by which the neurotrophins might influence synaptic plasticity.     

Differential expression of mRNAs for the NGF family of neurotrophic factors in the adult rat central olfactory system.

The cellular localization of mRNAs for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT3), in the rat central olfactory system was evaluated with in situ hybridization of 35S-labeled cRNA probes. In the main olfactory bulb, low levels of NGF and BDNF mRNA expression were detected. NGF mRNA was restricted to the glomerular region while BDNF mRNA was predominantly localized to the granule cell layer. No cellular hybridization to NT3 cRNA was seen. The accessory olfactory bulb did not express detectable levels of mRNA for any of the three related neurotrophic factors. Areas which receive olfactory bulb afferents expressed comparatively high levels of both NGF and BDNF mRNA. Cell labeling with cRNAs for NGF and BDNF occurred throughout the cellular layers of the anterior olfactory nucleus and in layers 2 and 3 of rostral piriform cortex. BDNF mRNA expression in these areas appeared more robust than that of NGF mRNA, while NT3 mRNA was not detectable. In contrast, tenia tecta exhibited dense labeling with the cRNAs for all three neurotrophic factors. The localization of NGF mRNA to primary target neurons of the olfactory nerve in the periglomerular region of the main olfactory bulb suggests that bulb cells may influence the ingrowth and continual turnover of olfactory sensory afferents. However, as there is a strong correlation between the distribution of neurotrophic factor mRNAs within rostral olfactory structures and the distribution of centrifugal cholinergic afferents, it is more likely that bulb-derived NGF, and possibly BDNF, act on the cholinergic neurons of the basal forebrain.