缺血性老年大鼠部分脑区及小脑内源性神经生长因子的变化

背景神经生长因子( nerve growth factor, NGF)在神经元的生长、存活、分化、保护神经元的退行性改变及神经损伤的自我保护与修复中具有重要作用,目前 NGF保护神经元的分子病理学机制还有许多需要深入探讨的. 目的观察脑缺血老年大鼠部分脑区及小脑内源性神经生长因子的变化. 设计 完全随机对照实验研究. 地点与材料本研究的地点为广州军区广州总医院实验科.材料为 36只 SD大鼠 2～ 2.5年龄,雌雄不限. 干预用夹闭两侧颈总动脉法建立不完全性脑缺血动物模型,将 SD大鼠随机分成正常对照组( A组)、假手术组( B组)、缺血 30 min再灌注 6 h( C组)、 12 h( D组)、 2 4h( E组)、 4 8h( F组)、 7 d( G组)和 14 d( H组),用免疫组织化学 ABC染色法检测部分脑区神经元及小脑 NGF的表达.在透射电镜下观察各组神经元超微结构变化. 主要观察指标各组神经元 NGF表达定性及定量观察. 结果除 A、 B组外,各组顶叶皮质神经元均有 NGF表达,其中 E组和 G组中量表达,神经元数量分别为( 58.4± 9.18) mm2和( 56.2± 10.87) mm2;除 A组、 B组、 F组和 H组外各组海马均有少量表达,神经元数量 C组为( 28.8± 6.42) mm2、 D组( 30.4± 12.12) mm2、 E组( 24.2± 5.18) mm2、 G组( 15.6± 4.39) mm2;小脑均没有表达;再灌注超过 48 h组海马神经元和小脑蒲肯野细胞损伤较重,顶叶皮质神经元轻度水肿. 结论老年大鼠在受到缺血性脑损伤时,内源性 NGF在大脑皮质和海马有部分表达,小脑始终没有表达.内源性 NGF对脑组织具有一定的保护作用,早期注射外源性 NGF可能对脑组织损伤后修复具有重要意义.     

神经生长因子预处理阿尔茨海默病大鼠海马神经原磷酸化Tau蛋白的变化

背景：神经生长因子能够促进胆碱能神经元的分化,决定轴突的生长,并可参与损伤神经的再生和功能修复。目的：进一步验证神经生长因子预处理对拟阿尔茨海默病模型大鼠脑内神经原纤维缠结和磷酸化Tau蛋白表达的影响。方法：将3-5月龄雄性Wistar大鼠随机分为3组：模型组将冈田酸微量注射至拟大鼠海马CA1区建立拟阿尔茨海默病大鼠模型;预处理组于造模前将神经生长因子注射至侧脑室;对照组用同样方法注入等体积的二甲亚砜作为对照。通过Morris水迷宫观察上述大鼠的行为学变化,分别用改进的Bielschowsky染色观察海马CA1区神经原纤维缠结,用免疫组织化学和免疫印迹法观察海马区磷酸化Tau蛋白表达的变化。结果与结论：拟阿尔茨海默病模型组大鼠出现认知、学习记忆能力减退;与对照组比较,模型组海马CA1区出现较多神经原纤维缠结,而且磷酸化的Tau蛋白表达增多;神经生长因子预处理组大鼠的上述症状明显改善。提示神经生长因子预处理可以显著改善拟阿尔茨海默病模型大鼠的学习记忆能力,抑制神经原纤维缠结的形成,减少磷酸化Tau蛋白的表达。     

促红细胞生成素对心肺复苏后大鼠海马神经元NGF、BDNF表达的影响

目的观察促红细胞生成素（EPO）对心肺复苏后大鼠海马神经生长因子（NGF）、脑源性神经营养因子（BDNF）表达的影响。方法采用窒息法制作大鼠呼吸心跳骤停模型,然后行心肺复苏术（CPR）。雄性Wistar大鼠60只,随机分3组：手术对照组（A组）、心肺复苏组（B组）、心肺复苏＋EPO（C组）。应用免疫组化法观察各组大鼠复苏后12 h海马神经元凋亡细胞、NGF及BDNF表达情况。结果与对照组（A组）相比心肺复苏组（B组）大鼠海马神经元NGF、BDNF表达明显降低（P〈0.05）,凋亡细胞明显增加（P〈0.01）;心肺复苏＋EPO（C组）NGF、BDNF表达明显增加,高于B组和A组（P〈0.01）,凋亡细胞明显降低（P〈0.05）,低于B组。结论 EPO能促进神经元NGF、BDNF的表达,减少神经细胞凋亡,对缺血、缺氧性神经元损伤有保护作用。     

Human neural progenitors deliver glial cell line-derived neurotrophic factor to parkinsonian rodents and aged primates

Glial cell line-derived neurotrophic factor (GDNF) has been shown to increase the survival and functioning of dopamine neurons in a variety of animal models and some recent human trials. However, delivery of any protein to the brain remains a challenge due to the blood/brain barrier. Here we show that human neural progenitor cells (hNPC) can be genetically modified to release glycosylated GDNF in vitro under an inducible promoter system. hNPC-GDNF were transplanted into the striatum of rats 10 days following a partial lesion of the dopamine system. At 2 weeks following transplantation, the cells had migrated within the striatum and were releasing physiologically relevant levels of GDNF. This was sufficient to increase host dopamine neuron survival and fiber outgrowth. At 5 weeks following grafting there was a strong trend towards functional improvement in transplanted animals and at 8 weeks the cells had migrated to fill most of the striatum and continued to release GDNF with transport to the substantia nigra. These cells could also survive and release GDNF 3 months following transplantation into the aged monkey brain. No tumors were found in any animal. hNPC can be genetically modified, and thereby represent a safe and powerful option for delivering growth factors to specific targets within the central nervous system for diseases such as Parkinson's.     

LY503430, a novel alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor potentiator with functional,neuroprotective and neurotrophic effects in rodent models of Parkinson's disease

Glutamate is the major excitatory transmitter in the brain. Recent developments in the molecular biology and pharmacology of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) subtype of glutamate receptors have led to the discovery of selective, potent, and systemically active AMPA receptor potentiators. These molecules enhance synaptic transmission and play important roles in plasticity and cognitive processes. In the present study, we first characterized a novel AMPA receptor potentiator, (R)-4'-[1-fluoro-1-methyl-2-(propane-2-sulfonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430), on recombinant human GLUA1-4 and native preparations in vitro and then evaluated the potential neuroprotective effects of the molecule in rodent models of Parkinson's disease. Results indicated that submicromolar concentrations of LY503430 selectively enhanced glutamate-induced calcium influx into human embryonic kidney 293 cells transfected with human GLUA1, GLUA2, GLUA3, or GLUA4 AMPA receptors. The molecule also potentiated AMPA-mediated responses in native cortical, hippocampal, and substantia nigra neurons. We also report here that LY503430 provided dose-dependent functional and histological protection in animal models of Parkinson's disease. The neurotoxicity after unilateral infusion of 6-hydroxydopamine into either the substantia nigra or the striatum of rats and that after systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice were reduced. Interestingly, LY503430 also had neurotrophic actions on functional and histological outcomes when treatment was delayed until well after (6 or 14 days) the lesion was established. LY503430 also produced some increase in brain-derived neurotrophic factor in the substantia nigra and a dose-dependent increases in growth associated protein-43 (GAP-43) expression in the striatum. Therefore, we propose that AMPA receptor potentiators offer the potential of a new disease modifying therapy for Parkinson's disease.     

Effect of dexamethasone on the expression of brain-derived neurotrophic factor and neurotrophin-3 messenger ribonucleic acids after forebrain ischemia in the rat

OBJECTIVE: To determine whether a large dose of dexamethasone affected brain damage induced by concurrent cerebral ischemia, we used in situ hybridization to examine the expression of brain-derived neurotrophic factor and neurotrophin-3 messenger ribonucleic acids (mRNAs) in rats with and without dexamethasone administration after transient forebrain ischemia. DESIGN: Prospective experimental study in rats. SETTING: Experimental laboratory in a teaching hospital and university. SUBJECTS: Eighty adult rats. INTERVENTIONS: Twenty minutes of transient forebrain ischemia was induced by occlusion of four vessels in lightly anesthetized rats. Thirty-six animals received dexamethasone (15 mg/kg, intraperitoneally) after initial reperfusion. Thirty-six dexamethasone-control rats were injected with saline, and the remaining animals underwent sham surgery but no ischemia or dexamethasone. MEASUREMENTS AND MAIN RESULTS: Using in situ hybridization, we determined hippocampal brain-derived neurotrophic factor and neurotrophin-3 mRNA expression 2, 4, 6, 12, and 24 hrs and 2, 3, 4, and 7 days after brain ischemia. Additionally, hippocampal CA1 region cell death was measured with Nissl stains. Both brain-derived neurotrophic factor and neurotrophin-3 mRNA exhibited a biphasic response after ischemia. Brain-derived neurotrophic factor mRNA showed two peaks of 4.07-fold and 2.84-fold increases relative to sham operation at 6 hrs and 2 days, respectively. Neurotrophin-3 mRNA initially decreased to 59% of sham levels at 4 hrs and then increased to 146% at 3 days before it returned to basal levels. When the ischemic rats were treated with dexamethasone, the elevation of brain-derived neurotrophic factor mRNA and the reduction of neurotrophin-3 mRNA level were prevented within the first 24 hrs, and hippocampal CA1 neurons were protected from ischemia-induced cell loss 7 days after brain ischemia. The protein levels of both brain-derived neurotrophic factor and neurotrophin-3 in general correspond to the mRNA levels in the hippocampal region. CONCLUSIONS: Dexamethasone modulates the intriguing temporal and spatial expression of brain-derived neurotrophic factor and neurotrophin-3 that predominantly supports neuronal innervation at different times after brain ischemia and also may provide specific trophic support for various neurons in the central nervous system.     

Beta adrenergic inhibition of capsaicin-induced, NK1 receptor-mediated nerve growth factor biosynthesis in rat skin

Excitation of primary afferent neurons stimulates the expression of cytokines and nerve growth factor (NGF) in innervated tissues. Since NGF is a neurotrophic and immunomodulatory factor contributing to inflammatory hyperalgesia and tissue response to injury, this study was conducted in order to investigate the mechanisms by which afferent neuron stimulation by topical application of capsaicin increases NGF in the rat skin. Thereby it was sought to identify possible targets for pharmacological modulation of NGF biosynthesis. Topical capsaicin (>1 mg/ml ethanol) caused a concentration- and time-dependent increase in the concentration of NGF in rat skin. The capsaicin-induced increase of NGF was not significantly affected by indomethacin administered at a dose (2 mg/kg) that abolishes prostaglandin E2 biosynthesis. The NGF increase was suppressed by treatment of rats with the selective tachykinin NK1 receptor antagonist SR140333 (0.1 mg/kg), and by the beta adrenergic agonist terbutaline (0.3 mg/kg). The effect of terbutaline was reversed by the beta adrenergic antagonist propranolol (1 mg/kg). Terbutaline also inhibited the increase in NGF caused by intraplantar injection of the NK1 receptor agonist substance P (SP), but did not significantly affect that caused by carrageenan. The results show that topical administration of capsaicin causes a primarily NK1 receptor-dependent increase in the NGF content of rat skin, which is susceptible to inhibition by beta adrenergic agonists. These observations not only suggest regulation of skin NGF biosynthesis by afferent neuronal and adrenergic mechanisms, but also indicate possible targets for pharmacological modulation of skin NGF biosynthesis.     

Comparison of galantamine and donepezil for effects on nerve growth factor, cholinergic markers, and memory performance in aged rats

This study was designed to determine 1) whether repeated exposures to the acetylcholinesterase inhibitors (AChEIs) galantamine (GAL) or donepezil (DON) resulted in positive effects on nerve growth factor (NGF) and its receptors, cholinergic proteins, and cognitive function in the aged rat, and 2) whether GAL had any advantages over DON given its allosteric potentiating ligand (APL) activity at nicotinic acetylcholine receptors. Behavioral tests (i.e., water maze and light/dark box) were conducted in aged Fisher 344 rats during 15 days of repeated (subcutaneous) exposure to either GAL (3.0 or 6.0 mg/kg/day) or DON (0.375 or 0.75 mg/kg/day). Forty-eight hours after the last drug injection, cholinergic receptors were measured by [(125)I]-(+/-)-exo-2-(2-iodo-5-pyridyl)-7-azabicyclo[2.2.1]heptane ([(125)I]IPH; epibatidine analog), (125)I-alpha-bungarotoxin ((125)I-BTX), [(3)H]pirenzepine ([(3)H]PRZ), and [(3)H]-5,11-dihydro-11-[((2-(2-((dipropylamino)methyl)-1-piperidinyl)ethyl)amino)carbonyl]-6H-pyrido(2,3-b)(1,4)-benzodiazepin-6-one methanesulfonate ([(3)H]AFDX-384, or [(3)H]AFX) autoradiography. Immunochemical methods were used to measure NGF, high (TrkA and phospho-TrkA)- and low (p75 neurotrophin receptor)-affinity NGF receptors, choline acetyltransferase (ChAT), and the vesicular acetylcholine transporter (VAChT) in memory-related brain regions. Depending on dose, both GAL and DON enhanced spatial learning (without affecting anxiety levels) and increased [(125)I]IPH, [(3)H]PRZ, and [(3)H]AFX (but decreased (125)I-BTX) binding in some cortical and hippocampal brain regions. Neither AChEI was associated with marked changes in NGF, NGF receptors, or VAChT, although DON did moderately increase ChAT in the basal forebrain and hippocampus. The results suggest that repeated exposures to either GAL or DON results in positive (and sustained) behavioral and cholinergic effects in the aged mammalian brain but that the APL activity of GAL may not afford any advantage over acetylcholinesterase inhibition alone.     

Hyperstimulation of striatal D2 receptors with sleep deprivation: Implications for cognitive impairment

Sleep deprivation interferes with cognitive performance but the mechanisms are poorly understood. We recently reported that one night of sleep deprivation increased dopamine in striatum (measured with [¹¹C]raclopride, a PET radiotracer that competes with endogenous dopamine for binding to D2 receptors) and that these increases were associated with impaired performance in a visual attention task. To better understand this association here we evaluate the relationship between changes in striatal dopamine (measured as changes in D2 receptor availability using PET and [¹¹C]raclopride) and changes in brain activation to a visual attention task (measured with BOLD and fMRI) when performed during sleep deprivation versus during rested wakefulness. We find that sleep induced changes in striatal dopamine were associated with changes in cortical brain regions modulated by dopamine (attenuated deactivation of anterior cingulate gyrus and insula) but also in regions that are not recognized targets of dopaminergic modulation (attenuated activation of inferior occipital cortex and cerebellum). Moreover, the increases in striatal dopamine as well as its associated regional activation and deactivation patterns correlated negatively with performance accuracy. These findings therefore suggest that hyperstimulation of D2 receptors in striatum may contribute to the impairment in visual attention during sleep deprivation. Thus, while dopamine increases in prefrontal regions (including stimulation of D1 receptors) may facilitate attention our findings suggest that hyperstimulation of D2 receptors in striatum may impair it. Alternatively, these associations may reflect a compensatory striatal dopamine response (to maintain arousal) that is superimposed on a larger response to sleep deprivation.     

Effect of tetrahydrocannabinols on 3H-acetylcholine biosynthesis in various rat brain slices.

The effects of delta8- and delta9-tetrahydrocannabinol on the biosynthesis of 3H-acetylcholine (ACh) from 3H-choline in cortical, hypothalamic and striatal rat brain slices were examined. The two cannabinols were found to inhibit the synthesis of 3H-ACh in the three brain regions. Treatment with cannabidiol did not alter ACh synthesis. Delta8-tetrahydrocannabinol was approximately twice as effective as the delta9-isomer. This effect was not associated with alterations in striatal and cortical choline acetyltransferase or with an impaired high-affinity uptake system for choline in the striatum. Treatment with delta8- and delta9-cannabinols, likewise, did not change striatal choline and ACh levels. Antagonism of the ACh biosynthesis inhibition occurred when slices from treated animals were incubated in depolarizing concentration of K+ ion. These results suggest that the inhibition of ACh synthesis observed in tetrahydrocannabinol-treated rats may be related to interference with the propagated action potential or with the depolarization process in cholinergic neurons.     

脑源性神经营养因子抗体对大脑中动脉阻塞大鼠缺血损伤的影响

AIM:To observe the effect of the antibody of brain derived neurotrophic factor(BDNF) by cortical microinjection on hippocampal ischemic injury rats.METHODS:Preparation of local cerebral ischemic reperfusion injury model: cortical stereostaxic approach, microinjection of BDNF antibody. Applied immunohistochemical method to observe distribution of BDNF in cortex after injection of the antibody,to observe the alteration of ischemic injury between control group and BDNF antibody group.RESULT: The volume of cerebral infarction in BDNF antibody group was larger than control group.CONCLUSION: BDNF has protection function for cerebral ischemia.     

Differential effects of glial cell line-derived neurotrophic factor (GDNF) in the striatum and substantia nigra of the aged Parkinsonian rat

Injection of an adenoviral (Ad) vector encoding human glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic (DA) neurons in the substantia nigra (SN) of young rats. As Parkinson's disease occurs primarily in aged populations, we examined whether chronic biosynthesis of GDNF, achieved by adenovirus-mediated delivery of a GDNF gene (AdGDNF), can protect DA neurons and improve DA-dependent behavioral function in aged (20 months) rats with progressive 6-OHDA lesions of the nigrostriatal projection. Furthermore, the differential effects of injecting AdGDNF either near DA cell bodies in the SN or at DA terminals in the striatum were compared. AdGDNF or control vector was injected unilaterally into either the striatum or SN. One week later, rats received a unilateral intrastriatal injection of 6-OHDA on the same side as the vector injection. AdGDNF injection into either the striatum or SN significantly reduced the loss of FG labelled DA neurons 5 weeks after lesion (P 相似文献   

In Vivo AAV1 Transduction With hRheb(S16H) Protects Hippocampal Neurons by BDNF Production

Recent evidence has shown that Ras homolog enriched in brain (Rheb) is dysregulated in Alzheimer''s disease (AD) brains. However, it is still unclear whether Rheb activation contributes to the survival and protection of hippocampal neurons in the adult brain. To assess the effects of active Rheb in hippocampal neurons in vivo, we transfected neurons in the cornu ammonis 1 (CA1) region in normal adult rats with an adeno-associated virus containing the constitutively active human Rheb (hRheb(S16H)) and evaluated the effects on thrombin-induced neurotoxicity. Transduction with hRheb(S16H) significantly induced neurotrophic effects in hippocampal neurons through activation of mammalian target of rapamycin complex 1 (mTORC1) without side effects such as long-term potentiation impairment and seizures from the alteration of cytoarchitecture, and the expression of hRheb(S16H) prevented thrombin-induced neurodegeneration in vivo, an effect that was diminished by treatment with specific neutralizing antibodies against brain-derived neurotrophic factor (BDNF). In addition, our results showed that the basal mTORC1 activity might be insufficient to mediate the level of BDNF expression, but hRheb(S16H)-activated mTORC1 stimulated BDNF production in hippocampal neurons. These results suggest that viral vector transduction with hRheb(S16H) may have therapeutic value in the treatment of neurodegenerative diseases such as AD.     

神经生长因子对大鼠脑缺血再灌注损伤的神经保护

目的探讨神经生长因子（NGF）对大鼠局灶性脑缺血再灌注损伤的保护作用。方法线栓法建立大鼠右侧大脑中动脉缺血-再灌注损伤模型,同时给予NGF治疗。检测肿瘤坏死因子-α（TNF-α）、自介素-1（IL-1）、白介素-6（IL-6）,丙二醛（MDA）及超氧化物歧化酶（SOD）含量及神经细胞的凋亡数。结果NGF组TNF-α、IL-1较缺血再灌注损伤（IR）组明显下降,差异有统计学意义。与IR组相比,NGF组SOD活性明显升高、MDA及IL-6含量明显下降,差异有统计学意义。神经细胞的凋亡检测发现,与IR组比较,NGF组凋亡细胞数明显降低,差异有统计学意义。结论NGF可以减轻炎症反应和改善氧自由基代谢,减少脑组织细胞的凋亡,对局灶性脑缺血再灌注损伤大鼠具有保护作用。     

Postischemic administration of Sendai virus vector carrying neurotrophic factor genes prevents delayed neuronal death in gerbils

Sendai virus (SeV) vector-mediated gene delivery of glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) prevented the delayed neuronal death induced by transient global ischemia in gerbils, even when the vector was administered several hours after ischemia. Intraventricular administration of SeV vector directed high-level expression of the vector-encoded neurotrophic factor genes, which are potent candidates for the treatment of neurodegenerative diseases. After occlusion of the bilateral carotid arteries of gerbils, SeV vector carrying GDNF (SeV/GDNF), NGF (SeV/NGF), brain-derived neurotrophic factor (SeV/BDNF), insulin-like growth factor-1 (SeV/IGF-1) or vascular endothelial growth factor (SeV/VEGF) was injected into the lateral ventricle. Administration of SeV/GDNF, SeV/NGF or SeV/BDNF 30 min after the ischemic insult effectively prevented the delayed neuronal death of the hippocampal CA1 pyramidal neurons. Furthermore, the administration of SeV/GDNF or SeV/NGF as late as 4 or 6 h after the ischemic insult also prevented the death of these neurons. These results indicate that SeV vector-mediated gene transfer of neurotrophic factors has high therapeutic potency for preventing the delayed neuronal death induced by transient global ischemia, and provides an approach for gene therapy of stroke.     

Aging does not alter brain muscarinic receptor-mediated phosphoinositide hydrolysis and its inhibition by phorbol esters, tetrodotoxin and receptor desensitization

The effects of aging on muscarinic receptor-mediated phosphoinositide (PI) hydrolysis in the brain were investigated in Fischer-344 rats. Oxotremorine-M stimulated this response to the same magnitude in young and old rats in the cerebral cortex, striatum, hippocampus, thalamus, hypothalamus and cerebellum, although maximal stimulation varied among brain regions within each age group. The PI response was also equally potentiated by elevated K+ or suppressed by tetrodotoxin in both age groups. In addition, a phorbol ester attenuated muscarinic receptor-mediated PI hydrolysis in the cerebral cortex to the same extent in young and aged rats. Moreover, preincubation with oxotremorine-M resulted in a similar down-regulation of cell-surface receptors and desensitization of receptor function regardless of age. Therefore, under our experimental conditions, PI hydrolysis in response to activation of brain muscarinic receptors does not appear to be sensitive to aging-related alterations.     

Chronic cold exposure affects the antioxidant defense system in various rat tissues

BACKGROUND: Chronic exposure to stress alters the normal body homeostasis and, hence, leads to the development of various human pathologies, which might involve alterations in the antioxidant defense system. We studied the effect of chronic cold exposure on oxidative stress and antioxidant defense system in various rat tissues. METHODS: Male albino rats (Wistar strain), 2-3 months old, were exposed to 3 weeks of cold treatment. Antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) were measured in addition to the antioxidants, ascorbic acid (AsA) and glutathione (GSH), and the prooxidants, lipid peroxides (LPO) and xanthine oxidase (XOD), in brain, heart, kidney, liver and small intestine using standard protocols. RESULTS: Chronic cold exposure resulted in a significant increase in LPO in all the tissues studied while XOD was increased in the brain and intestine. Total SOD activity was significantly decreased in all the tissues, whereas CAT activity was significantly increased in the kidney and decreased in heart, liver and intestine in the animals exposed to cold. GPx activity was increased only in the brain and intestine of stressed rats. Chronic cold exposure resulted in significant decrease in GR activity in heart, liver and intestine. GST activity was increased (except heart) and GSH was significantly decreased in all the tissues in treated rats. AsA was increased in kidney and intestine but decreased in heart of stressed animals. CONCLUSIONS: The observed changes in the antioxidant defense system are tissue specific, but it is evident that chronic exposure to cold leads to oxidative stress by displacing the prooxidant-antioxidant balance of this defense system by increasing the prooxidants while depleting the antioxidant capacities.     

Correlation between analgesia and the decrease of acetylcholine turnover rate in cortex and hippocampus elicited by morphine, meperidine, viminol R2 and azidomorphine.

In rats, an ED50 for analgesia of morphine, meperidine, viminol R2 or azidomorphine decreases the turnover rate of acetylcholine (TRACh) in cortex and hippocampus. These four analgetics fail to change to TRACh in striatum when given in a dose range from ED30 for analgesia up to a cataleptic dose. Viminol S2, a nonanalgesic stereoisomer of vimonol R2, fails to decrease the TRACh in cortex and hippocampus. Naltrexone, an opiate antagonist, also fails to change the cortical and hippocampal TRACh but it antagonizes the decrease in cortical and hippocampal TRACh elicited by the four analgetics. Since the ED50 of these four analgetics fails to change the TRACh in striatum which contains a high density of opiate receptors and intrinsic cholinergic neurons, but decreases the TRACh in hippocampus and cortex which contain a low density of opiate receptors, it can be inferred that opiate receptors are not exclusively involved in the regulation of TRACh. However, the results suggest that certain cholinergic pathways participate in the mediation of analgesia.     

Improvement of spatial learning and memory after adenovirus-mediated transfer of the nerve growth factor gene to aged rat brain

Adenovirus-mediated transfer of the nerve growth factor gene promotes significant recovery of age-related cholinergic neuronal deficits in aged rats, but the effects of such treatment on cognitive dysfunction remain unclear. Herein we report a beneficial effect of first-generation adenovirus-mediated nerve growth factor gene transfer (AdNGF) on the spatial learning and memory of aged rats. The NGF protein was detected by enzyme-linked immunosorbent assay in cerebrospinal fluid as early as 3 days after gene transfer and was expressed for at least 30 days. Escape latency in the Morris water maze hidden-platform test was significantly improved on day 8 postinoculation in memory-impaired rats treated with AdNGF as well as at later testing intervals. Ultimately, the escape latency values for the AdNGF group become indistinguishable from those for aged rats with normal learning capacity. Immunohistochemical analysis of septal cholinergic neurons for choline acetyltransferase (ChAT) showed significant increases in both the number and somal distribution of ChAT-positive cells after inoculation of memory-impaired rats with AdNGF. Improvement in memory performance was positively correlated with increases in both NGF concentration in cerebrospinal fluid (r = 0.73, p = 0.005) and the number of ChAT-staining cells (r = 0.77, p = 0.0022). We conclude that AdNGF can improve cognitive function in memory-impaired aged rats and, with refinements in vector-driven expression of the transgene, may prove suitable for use in humans.     

Selective vulnerability of glutathione metabolism and cellular defense mechanisms in rat striatum to manganese

The present findings provide experimental evidence for the hypothesis that compromised cellular defense mechanisms, i.e., glutathione (GSH), GSH-peroxidase and catalase in the brain may be involved in neuronal degeneration caused by manganese (Mn) neurotoxicity. Moreover, data are presented demonstrating that the striatum is particularly susceptible to the deleterious effects of Mn. Specifically, exposure to subchronic MnCl2 produced significant reductions in GSH-peroxidase activity in the cytosol and mitochondrial fractions of the whole brain and the striatum. The decrease in GSH-peroxidase was most pronounced in the mitochondrial fraction of the striatum where the activity was reduced to 35% of the control. Catalase activity was also decreased in the striatum of rats treated with Mn but not in the whole brain. GSH content was markedly depleted (20% of the control) in the striatum, although only modestly decreased in whole brain (80% of the control). The alterations in the above parameters were accompanied by depletion of dopamine and dopamine metabolites in the striatum. The treatment of rats with Mn also decreased the activity of oxidized glutathione-reductase; the same treatment increased the activity of gamma-glutamyltranspeptidase. The activity of gamma-glutamylcysteine synthetase was not altered by Mn. The possible relevancy of the findings of this study to understanding the mechanism of Mn neurotoxicity of dopamine systems is discussed.