The expression, localization and functional significance of beta-nerve growth factor in the central nervous system

Morphogenetic theory of mental and cognitive disorders: the role of neurotrophic and guidance molecules

Mental illness and cognitive disorders represent a serious problem for the modern society. Many studies indicate that mental disorders are polygenic and that impaired brain development may lay the ground for their manifestation. Neural tissue development is a complex and multistage process that involves a large number of distant and contact molecules. In this review, we have considered the key steps of brain morphogenesis, and the major molecule families involved in these process. The review provides many indications of the important contribution of the brain development process and correct functioning of certain genes to human mental health. To our knowledge, this comprehensive review is one of the first in this field. We suppose that this review may be useful to novice researchers and clinicians wishing to navigate the field.

Fornix degeneration in risk factors of Alzheimer's disease, possible trigger of cognitive decline

Risk factors of late-onset Alzheimer's disease (AD) such as aging, type 2 diabetes, obesity, heart failure, and traumatic brain injury can facilitate the appearance of cognitive decline and dementia by triggering cerebrovascular pathology and neuroinflammation. White matter (WM) microstructure and function are especially vulnerable to these conditions. Microstructural WM changes, assessed with diffusion weighted magnetic resonance imaging, can already be detected at preclinical stages of AD, and in the presence of the aforementioned risk factors. Particularly, the limbic system and cortico-cortical association WM tracts, which myelinate late during brain development, degenerate at the earliest stages. The fornix, a C-shaped WM tract that originates from the hippocampus, is one of the limbic tracts that shows early microstructural changes. Fornix integrity is necessary for ensuring an intact executive function and memory performance. Thus, a better understanding of the mechanisms that cause fornix degeneration is critical in the development of therapeutic strategies aiming to prevent cognitive decline in populations at risk. In this literature review, i) we deepen the idea that partial loss of forniceal integrity is an early event in AD, ii) we describe the role that common risk factors of AD can play in the degeneration of the fornix, and iii) we discuss some potential cellular and physiological mechanisms of WM degeneration in the scenario of cerebrovascular disease and inflammation.

The Nerve Growth Factor Metabolic Pathway Dysregulation as Cause of Alzheimer's Cholinergic Atrophy

The cause of the loss of basal forebrain cholinergic neurons (BFCNs) and their terminal synapses in the cerebral cortex and hippocampus in Alzheimer's disease (AD) has provoked a decades-long controversy. The cholinergic phenotype of this neuronal system, involved in numerous cognitive mechanisms, is tightly dependent on the target-derived nerve growth factor (NGF). Consequently, the loss of BFCNs cholinergic phenotype in AD was initially suspected to be due to an NGF trophic failure. However, in AD there is a normal NGF synthesis and abundance of the NGF precursor (proNGF), therefore the NGF trophic failure hypothesis for the atrophy of BCNs was abandoned. In this review, we discuss the history of NGF-dependency of BFCNs and the atrophy of these neurons in Alzheimer's disease (AD). Further to it, we propose that trophic factor failure explains the BFCNs atrophy in AD. We discuss evidence of the occurrence of a brain NGF metabolic pathway, the dysregulation of which, in AD explains the severe deficiency of NGF trophic support for the maintenance of BFCNs cholinergic phenotype. Finally, we revise recent evidence that the NGF metabolic dysregulation in AD pathology starts at preclinical stages. We also propose that the alteration of NGF metabolism-related markers in body fluids might assist in the AD preclinical diagnosis.

Effects of intranasally-delivered pro-nerve growth factors on the septo-hippocampal system in healthy and diabetic rats

Pro-nerve growth factor (proNGF) is the predominant form of NGF in the brain and its levels increase in neurodegenerative diseases. The balance between NGF receptors may explain the contradictory biological activities of proNGF. However, the specific role of the two main proNGF variants is mostly unexplored. proNGF-A is prevalently expressed in healthy brain, while proNGF-B content increases in the neuro-degenerating brain. Recently we have investigated in vitro the biological action of native mouse proNGF variants. To gain further insights into the specific functions of the two proNGFs, here we intranasally delivered mouse-derived proNGF-A and proNGF-B to the brain parenchyma of healthy and diabetic rats, the latter characterized by dysfunction in spatial learning and memory, in the septo-hippocampal circuitry and by relative increase in proNGF-B hippocampal levels. Exogenous proNGF-B induces depression of hippocampal DG-LTP and impairment of hippocampal neurogenesis in healthy animals, with concomitant decrease in basal forebrain cholinergic neurons and cholinergic fibers projecting to the hippocampus. proNGF-A, while ineffective in healthy animals, rescues the diabetes-induced impairment in DG-LTP and hippocampal neurogenesis, promoting the concomitant recovery of the basal forebrain cholinergic phenotype. Our experimental evidences suggest that the balance between different proNGFs may influence the development and progression of neurodegenerative diseases.

Advances in ex vivo models and lab-on-a-chip devices for neural tissue engineering

The technologies related to ex vivo models and lab-on-a-chip devices for studying the regeneration of brain, spinal cord, and peripheral nerve tissues are essential tools for neural tissue engineering and regenerative medicine research. The need for ex vivo systems, lab-on-a-chip technologies and disease models for neural tissue engineering applications are emerging to overcome the shortages and drawbacks of traditional in vitro systems and animal models. Ex vivo models have evolved from traditional 2D cell culture models to 3D tissue-engineered scaffold systems, bioreactors, and recently organoid test beds. In addition to ex vivo model systems, we discuss lab-on-a-chip devices and technologies specifically for neural tissue engineering applications. Finally, we review current commercial products that mimic diseased and normal neural tissues, and discuss the future directions in this field.

Deep brain stimulation: potential for neuroprotection

Over the last two decades there has been an exponential rise in the number of patients receiving deep brain stimulation (DBS) to manage debilitating neurological symptoms in conditions such as Parkinson's disease, essential tremor, and dystonia. Novel applications of DBS continue to emerge including treatment of various psychiatric conditions (e.g. obsessive-compulsive disorder, major depression) and cognitive disorders such as Alzheimer's disease. Despite widening therapeutic applications, our understanding of the mechanisms underlying DBS remains limited. In addition to modulation of local and network-wide neuronal activity, growing evidence suggests that DBS may also have important neuroprotective effects in the brain by limiting synaptic dysfunction and neuronal loss in neurodegenerative disorders. In this review, we consider evidence from preclinical and clinical studies of DBS in Parkinson's disease, Alzheimer's disease, and epilepsy that suggest chronic stimulation has the potential to mitigate neuronal loss and disease progression.

Nucleus Basalis of Meynert Stimulation for Dementia: Theoretical and Technical Considerations

Deep brain stimulation (DBS) of nucleus basalis of Meynert (NBM) is currently being evaluated as a potential therapy to improve memory and overall cognitive function in dementia. Although, the animal literature has demonstrated robust improvement in cognitive functions, phase 1 trial results in humans have not been as clear-cut. We hypothesize that this may reflect differences in electrode location within the NBM, type and timing of stimulation, and the lack of a biomarker for determining the stimulation's effectiveness in real time. In this article, we propose a methodology to address these issues in an effort to effectively interface with this powerful cognitive nucleus for the treatment of dementia. Specifically, we propose the use of diffusion tensor imaging to identify the nucleus and its tracts, quantitative electroencephalography (QEEG) to identify the physiologic response to stimulation during programming, and investigation of stimulation parameters that incorporate the phase locking and cross frequency coupling of gamma and slower oscillations characteristic of the NBM's innate physiology. We propose that modulating the baseline gamma burst stimulation frequency, specifically with a slower rhythm such as theta or delta will pose more effective coupling between NBM and different cortical regions involved in many learning processes.

Nerve Growth Factor: Early Studies and Recent Clinical Trials

Since its discovery, nerve growth factor (NGF) has long occupied a critical role in developmental and adult neurobiology for its many important regulatory functions on the survival, growth and differentiation of nerve cells in the peripheral and central nervous system. NGF is the first discovered member of a family of neurotrophic factors, collectively indicated as neurotrophins, (which include brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin 4/5). NGF was discovered for its action on the survival and differentiation of selected populations of peripheral neurons. Since then, an enormous number of basic and human studies were undertaken to explore the role of purified NGF to prevent the death of NGF-receptive cells. These studies revealed that NGF possesses important therapeutic properties, after topical administration, on human cutaneous pressure ulcer, corneal ulcers, glaucoma, retinal maculopathy, Retinitis Pigmentosa and in pediatric optic gliomas and brain traumas. The aim of this review is to present our previous, recent and ongoing clinical studies on the therapeutic properties of NGF.

Nerve growth factor-potentiating benzofuran derivatives from the medicinal fungus Phellinus ribis

Four new benzofuran derivatives, ribisin A (1), ribisin B (2), ribisin C (3), and ribisin D (4), were isolated from the MeOH extract of the fruiting bodies of Phellinus ribis. Their structures including their absolute configurations were determined by NMR and CD exciton chirality methods. Compounds 1-4 were found to promote neurite outgrowth in NGF-mediated PC12 cells at concentrations ranging from 1 to 30 μM. The structure-activity relationships of these compounds are also discussed.

Spirocyclic nortriterpenoids with NGF-potentiating activity from the fruits of Leonurus heterophyllus

Four new spirocyclic nortriterpenoids, leonurusoleanolide A (1), leonurusoleanolide B (2), leonurusoleanolide C (3), and leonurusoleanolide D (4), were isolated from the MeOH extract of the fruits of Leonurus heterophyllus. Compounds 1 and 2, and compounds 3 and 4, were found to exist as equilibrium mixtures of trans and cis isomers. Mixtures of 1 and 2, and 3 and 4, significantly enhanced the neurite outgrowth of nerve growth factor-treated PC12 cells at concentrations ranging from 1 to 30 μM. Compound 8 was also found to have a neurite outgrowth-promoting effect at concentrations of 1 and 10 μM. The structure-activity relationship of these compounds is discussed.

Effect of Tremella fuciformis on the neurite outgrowth of PC12h cells and the improvement of memory in rats

We investigated the neuritogenic effects of Tremella fuciformis (TF), which has been valued in traditional Chinese medicine as a remedy with nutritive and tonic actions, on PC12h cells. The cognitive improving effects of TF on scopolamine-induced (2 mg/kg, s.c.) amnesia in rats were also evaluated with using the Morris water maze task and by performing choline acetyltransferase (ChAT) immunohistochemistry. The water extract of TF (0.01-1 microg/ml) promoted neurite outgrowth of the PC12h cells in a dose dependent manner. TF was highly efficient at the concentration range of 0.1-1 microg/ml. Oral daily treatment with TF (100 or 400 mg/kg) for 14 consecutive days significantly reversed the scopolamine-induced deficit in learning and memory, and it alleviated decrease in cholinergic immunoreactivity induced by scopolamine in the medial septum and hippocampus. The results demonstrate that the promotion of neuritogenesis in neuronal culture cells by TF water extract is related with its activity for improving the performance of rats on a spatial learning and memory task. Moreover, the impairments of spatial learning and memory may be attributable to the decrease in activation of the septohippocampal cholinergic system and that TF ameliorated learning and memory deficits partly through its increasing the central cholinergic activity. Therefore, TF could represent a potentially useful agent that is able to improve the function of impaired cognitive processes.

Beta-adrenoreceptor antagonists attenuate brain injury after transient focal ischemia in rats

Beta-adrenoreceptor antagonists experimentally reduce cardiac and renal injury after ischemia and are also clinically useful for myocardial infarction and severe burns. In addition, beta-adrenoreceptor antagonists provide neuroprotective effects after focal cerebral ischemia in experimental settings. We conducted the present study to compare the neuroprotective effects of several beta-adrenoreceptor antagonists in rat transient focal cerebral ischemia. Halothane-anesthetized normothermic adult male Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion using the intraluminal suture technique confirmed by laser Doppler flowmetry. Rats received an IV infusion of saline 0.5 mL/h, propranolol 100 microg x kg(-1) x min(-1), carvedilol 4 microg x kg(-1) x min(-1), esmolol 200 microg x kg(-1) x min(-1), or landiolol 50 microg x kg(-1) x min(-1) (n = 6 in each group). Infusion was initiated 30 min before middle cerebral artery occlusion and continued for 24 h. Additional rats received esmolol 50 microg x kg(-1) x min(-1) or landiolol 10 microg x kg(-1) x min(-1) intrathecally (IT) via the cisterna magna (n = 5 in each group), according to the same experimental protocol. The neurological deficit score was evaluated at 22 h after reperfusion, and the brains were removed and stained with triphenyltetrazolium chloride for evaluation of infarct volume. Additional rats that received saline, esmolol, and landiolol IV (n = 6 in each group) were allowed to survive for 7 days followed by measurement of infarct size. Neurological deficit scores were smaller in rats treated with propranolol-IV, carvedilol-IV, esmolol-IV, landiolol-IV, esmolol-IT, and landiolol-IT compared with saline-treated rats (P < 0.05). Cortical and striatum infarct volumes were less in the rats receiving beta-adrenoreceptor antagonists via either IV or IT than in saline-treated rats (P < 0.05). We conclude that beta-adrenoreceptor antagonists improve neurological and histological outcomes after transient focal cerebral ischemia in rats independent of administration route.

CAAT/enhancer-binding protein delta and cAMP-response element-binding protein mediate inducible expression of the nerve growth factor gene in the central nervous system

Nerve growth factor (NGF) synthesis in the rat cerebral cortex is induced by the beta2-adrenergic receptor agonist clenbuterol (CLE). Because NGF is a crucial neurotrophic factor for basal forebrain cholinergic neurons, defining the mechanisms that regulate its transcription is important for developing therapeutic strategies to treat pathologies of these neurons. We previously showed that the transcription factor CCAAT/enhancer-binding protein delta (C/EBPdelta) contributes to NGF gene regulation. Here we have further defined the function of C/EBPdelta and identified a role for cAMP response element-binding protein (CREB) in NGF transcription. Inhibition of protein kinase A in C6-2B glioma cells suppressed CLE induction of an NGF promoter-reporter construct, whereas overexpression of protein kinase A increased NGF promoter activity, particularly in combination with C/EBPdelta. A CRE-like site that binds CREB was identified in the proximal NGF promoter, and C/EBPdelta and CREB were found to associate with the NGF promoter in vivo. Deletion of the CRE and/or C/EBP sites reduced CLE responsiveness of the promoter. In addition, ectopic expression of C/EBPdelta in combination with CLE treatment increased endogenous NGF mRNA levels in C6-2B cells. C/EBPdelta null mice showed complete loss of NGF induction in the cerebral cortex following CLE treatment, demonstrating a critical role for C/EBPdelta in regulating beta2-adrenergic receptor-mediated NGF expression in vivo. Thus, our findings demonstrate a critical role for C/EBPdelta in regional expression of NGF in the brain and implicate CREB in CLE-induced NGF gene transcription.

Increased spinal cord NGF levels in rats with cobalamin (vitamin B12) deficiency

We have recently demonstrated that the neuropathological morphological alterations caused by cobalamin (Cbl) deficiency in the rat central nervous system are related to the vitamin's inability to modulate the synthesis of some neurotoxic and neurotrophic agents in opposite directions. In the present study, we measured nerve growth factor (NGF) levels in the spinal cord (SC) and cerebrospinal fluid (CSF) of rats made Cbl-deficient (Cbl-D) by means of total gastrectomy (TG) or a Cbl-D diet. In both cases, Cbl deficiency increased SC and CSF NGF levels after the appearance of myelinolytic lesions in the SC white matter (SCWM) (i.e. after the second post-TG month), and these changes were normalised by Cbl treatment in the 4-month-totally-gastrectomised (TGX) rats. Intracerebroventricular (i.c.v.) anti-NGF-antibody treatment prevented the onset of the myelinolytic SCWM lesions in the 2-month-TGX rats (i.e. when SC and CSF NGF levels are still normal) and normalised the ultrastructure of the SCWM in the 4-month-TGX rats, which was however worsened by the i.c.v. administration of NGF. These findings demonstrate that: (i) Cbl deficiency increases SC and CSF NGF levels; and (ii) endogenous NGF seems to play a noxious role in the progression of rat Cbl-D central neuropathy.

Effects of huperzine A on secretion of nerve growth factor in cultured rat cortical astrocytes and neurite outgrowth in rat PC12 cells

AIM

To study the effects of huperzine A (HupA) on neuritogenic activity and the expression of nerve growth factor (NGF).

METHODS

After being treated with 10 micromol/L HupA, neurite outgrowth of PC12 cells was observed and counted under phase-contrast microscopy. Mitogenic activity was assayed by [3H]thymidine incorporation. Cell cytotoxicity was evaluated by lactate dehydrogenase (LDH) release. AChE activity, mRNA and protein expression were measured by the Ellman method, RT-PCR, and Western blot, respectively. NGF mRNA and protein levels were determined by RT-PCR and ELISA assays.

RESULTS

Treatment of PC12 cells with 10 micromol/L HupA for 48 h markedly increased the number of neurite-bearing cells, but caused no significant alteration in cell viability or other signs of cytotoxicity. In addition to inhibiting AChE activity, 10 micromol/L HupA also increased the mRNA and protein levels of this enzyme. In addition, following 2 h exposure of the astrocytes to 10 micromol/L HupA, there was a significant up-regulation of mRNA for NGF and P75 low-affinity NGF receptor. The protein level of NGF was also increased after 24 h treatment with HupA.

CONCLUSION

Our findings demonstrate for the first time that HupA has a direct or indirect neurotrophic activity, which might be beneficial in treatment of neurodegenerative disorders such as Alzheimer disease.

Nerve growth factor and its functional receptor TrkA are up-regulated in murine decidual tissue of stress-triggered and substance P-mediated abortion

PROBLEM

Stress, elicited by environmental and social conditions, is known to affect the homeostasis of the nervous, endocrine and immune systems. In pregnancy, perceived stress results in a predomination of inflammatory abortion-associated Th1 cytokines over immunosuppressive, pregnancy-protective-associated Th2 cytokines, putatively via neuropeptide substance P (SP). Nerve growth factor (NGF), an important trophic factor for sympathetic neurons, has been implicated in the responsiveness of immune-competent cells through its functional receptor, tropomyosin receptor kinase (TrkA). Thus, the aim of the present study was to identify a cross-talk between distinct neurotrophic and immune mediators in pregnancy maintenance.

METHOD OF STUDY

Using immune fluorescence, we evaluated decidual and placental expression of NGF and TrkA on gestation day (gd) 13.5 in the abortion-prone mouse model CBA/J x DBA/2J in (1) CBA/J female control mice; (2) CBA/J mice exposed to stress on gd 5.5; and (3) CBA/J mice injected with SP on gd 5.5 to mimick stress perception.

RESULTS

Stress and SP injection significantly increased the abortion rate and up-regulated decidual NGF and TrkA expression compared with the control. Stress, but not SP injection down-regulated placental NGF, whereas no changes in placental TrkA were observed.

CONCLUSION

Our data suggest a functional role for NGF in stress-triggered, SP-mediated abortion.

Differences in the regulation of BDNF and NGF synthesis in cultured neonatal rat astrocytes

Using a new brain-derived neurotrophic factor (BDNF) specific enzyme-immunoassay, we determined the basal cellular content of BDNF protein in neonatal rat astrocytes in primary culture, thus confirming the ability of astrocytes to synthesize BDNF in addition to nerve growth factor (NGF). We subsequently monitored the influence of different pharmacological agents: neurotransmitter receptor agonists, cytokines, and second messenger up-regulators, on the synthesis of BDNF and NGF. Marked differences in the regulation of their synthesis by the above pharmacological agents were observed in our study. The basal cellular levels of BDNF protein in cultured neonatal rat cortical and cerebellar astrocytes were 15.9 +/- 0.3 and 18.7 +/- 0.4 pg BDNF/mg cell protein, respectively, and differ significantly between astrocytes from different brain regions, whereas NGF levels were the same (16.1 +/- 0.3 and 16.2 +/- 0.7 pg NGF/mg cell protein, respectively). Screening different neurotransmitter systems for their influence on BDNF and NGF synthesis in cortical astrocytes revealed that dopamine (0.15 mM) is a potent up-regulator of BDNF protein synthesis in astrocytes, while kainic acid (50 microM) and histamine (1 microM) did not raise the cellular level of BDNF protein. Dopamine had no influence on NGF synthesis, while kainic acid caused minor, and histamine marked, elevation of NGF cellular content. Tumor necrosis factor-alpha (30 ng/ml) and interleukin-1beta (10 U/ml) treatments did not influence BDNF synthesis, whereas they markedly increased NGF protein cellular level. We also confirmed (using forskolin (20 microM) and phorbol 12-myristate 13-acetate (TPA) (100 nM)) that adenylate cyclase and protein kinase C participate in the downstream signaling responsible for the stimulation of BDNF synthesis, whereas in the regulation of NGF synthesis only the participation of protein kinase C was confirmed. Our results indicate that astrocyte-derived neurotrophins could play a role in distinct brain functions under physiological conditions and in the pathogenesis as well as possible treatment of different neurodegenerative disorders.

Carnitine: a neuromodulator in aged rats

A wide range of morphological and biochemical changes occur in the central nervous system with increasing age. L-carnitine, a naturally occurring compound, plays a vital role in fatty acid transport across the mitochondrial membrane. L-carnitine (300 mg/kg body wt/day) was administered intraperitoneally to young and old male Wistar rats for 7, 14, and 21 days. Carnitine, dopamine, epinephrine, and serotonin levels were assayed in discrete regions of the brain. Carnitine supplementation increased the levels of dopamine, epinephrine, and serotonin in the experimental animals in our study. Response to carnitine supplementation varied among the brain regions that have been studied. The regions rich in cholinergic neurons such as the cortex, hippocampus, and striatum showed more response after 21 days of carnitine treatment. The results of the present study suggest the role of L-carnitine as a neuromodulator and antiaging medication.

Nerve growth factor attenuates hippocampal cholinergic deficits and operant learning impairment in rats with entorhinal cortex lesions

In the present study we investigated whether continuous intraventricular nerve growth factor (NGF) infusion could ameliorate hippocampal cholinergic deficits and learning impairment following entorhinal cortex lesions. Rats with such lesions received continuous intraventricular infusions of NGF or vehicle. Unlesioned rats with a sham operation were studied as controls. After learning sessions, a dialysis probe was implanted in the CA3 hippocampal region. In addition, brain sections were stained for synaptophysin immunoreactivity. In rats undergoing surgical procedures similar to those in the behavioral study, brains were processed for acetylcholinesterase (AChE) histochemistry. NGF-treated rats showed partial amelioration of lesion-associated hippocampal acetylcholine (ACh) efflux deficits and fixed-interval schedule learning impairment compared with vehicle-treated rats. Histochemical, immunohistologic, and microdensitometric analyses confirmed greater density of AChE-positive fibers and synaptophysin immunoreactivity in CA3, in NGF-treated rats relative to vehicle-treated rats, although not as great as in sham-operation rats, indicating partial recovery in NGF-treated rats. These results suggest that enhanced performance of the learning task with NGF treatment was related to improved hippocampal cholinergic function: specifically, increased cholinergic neurotransmission resulting from NGF effects on cholinergic neurons and presynaptic terminals.

NGF induces appearance of adult-like response to spatial novelty in 18-day male mice

We investigated the effects of Nerve Growth Factor (NGF) administration on the maturation of reactivity to spatial and non-spatial novelty in developing mice. CD-1 mice of both sexes received intracerebral administration of NGF on postnatal day (pnd) 15, and their response to object displacement (spatial novelty) and object substitution (object novelty) were assessed in a spatial open-field with four objects on pnd 18 or 28. On pnd 18, NGF induced only in males precocious appearance of spatial novelty discrimination, while increasing choline acetyltransferase activity in neocortex and hippocampus of both sexes. The behavioral and neurochemical effects disappeared by pnd 28. NGF triggers adult-like responding to spatial novelty in developing mice and such effect is gender-specific.

Prenatal choline supplementation increases NGF levels in the hippocampus and frontal cortex of young and adult rats

Female Sprague-Dawley rats received approximately 300 mg/kg per day of choline chloride through their drinking water on days 11 of pregnancy through birth and the level of nerve growth factor (NGF) in the hippocampus and frontal cortex of their male offspring was measured at 20 and 90 days of age. Prenatal choline supplementation caused significant increases in hippocampal NGF levels at 20 and 90 days of age, while levels of NGF in the frontal cortex were elevated in choline-supplemented rats at 20 days of age, but not 90 days of age. These results suggest that increases in NGF levels during development or adulthood may be one mechanism underlying improvements in spatial and temporal memory of adult rats exposed to elevated levels of choline chloride perinatally.

Nerve Growth Factor Regulates Expression of the Nerve Growth Factor Receptor Gene in Adult Sensory Neurons

Sensory neurons of the adult rat dorsal root ganglion (DRG) can be maintained in culture in the absence of nerve growth factor (NGF). We have thus used dissociated cultures of these neurons to study effects of NGF on the regulation of expression of mRNA encoding the nerve growth factor receptor (NGF-R). In the absence of NGF, levels of NGF-R mRNA remained constant for 7 days in cultures of adult rat DRG neurons. In the presence of NGF, NGF-R mRNA levels rose two - three-fold after 2 days, reaching plateau levels (five - six-fold elevation) after 5 days. This NGF-induced up-regulation could be demonstrated even after prior NGF-deprivation for 3 - 4 days. NGF had no effect upon NGF-R mRNA levels in DRG non-neuronal cells. Epidermal growth factor (EGF), fibroblast growth factor (FGF) and ciliary neurotrophic factor (CNTF) were without effect on NGF-R mRNA levels, but 8-bromo-cAMP decreased NGF-R mRNA levels by 65% after 2 days. NGF also induced a rapid (30 min) rise in expression of c-fos in DRG neurons, but not in non-neuronal cells. Our results suggest that endogenous levels of NGF may regulate the expression of NGF-R in vivo.

Regulation of Neurotrophin mRNA Expression in the Rat Brain by Glucocorticoids

Northern blot analysis was used to examine the effects of glucocorticoids on neurotrophin mRNA expression in the rat cerebral cortex and hippocampus. The results show that 3 days after adrenalectomy the mRNA levels for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) decreased significantly in both these regions. In adrenalectomized animals given dexamethasone replacement the mRNA levels for the three neurotrophins were restored to control levels. The effect of a single dose of dexamethasone (5 mg/kg) administered i.p. to intact animals on the expression of neurotrophins was also examined. NGF and NT-3 mRNAs showed a 2.5-fold and a 1.4-fold increase, respectively, during the first 4 h after the injection. The increase was followed by a decrease, with levels approximately 50% of control 24 and 48 h after the injection. In contrast, the level of BDNF mRNA did not change during the first 10 h after the injection, but decreased to 70% of control 48 h after the injection. These data indicate that glucocorticoids regulate neurotrophin mRNA expression both in the cortex and in the hippocampus, and suggest further that the known effects of glucocorticoids on neuronal survival in the brain could be due to changes in the levels of neurotrophins in the brain.

Amelioration of cholinergic neurons dysfunction in aged rats depends on the continuous supply of NGF

The present study was designed to examine whether NGF-induced improvement in morphology of senile basal forebrain cholinergic neurons persist after discontinuation of NGF treatment. Trophic effect of continuous intraventricular infusion of NGF was tested in the 4- and 28 months old male Wistar rats immediately after cessation of NGF and 3 or 6 weeks after termination of treatment. Immunohistochemical procedure for ChAT, TrkA, and p75(NTR) receptor has been applied to identify cholinergic cells in the basal forebrain structures. Using the quantitative image analyzer, morphometric and densitometric parameters of cholinergic cells were measured. In untreated 28-month-old rats a reduction in the number, size and intensity of staining of cholinergic neurons was observed in all basal forebrain structures. NGF significantly improved morphological parameters of ChAT- and TrkA-positive cells in aged rats. In 28-month-old rats tested within 3 and 6 weeks after discontinuation of infusion a renewed progressive deterioration of cholinergic phenotype of basal forebrain neurons was observed when compared with the NGF-treated immediately tested group. The parallel staining for p75(NTR) revealed normal morphology of the basal forebrain neurons, despite of the age of rats or the NGF treatment. Analysis of Nissl stained sections also showed that 28-month-old rats did not display significant losses of neurons in the basal forebrain when compared with the young animals. These findings demonstrate that senile impairment of cholinergic neurons is induced by a loss of cholinergic phenotype rather than an acute degeneration of cell bodies. NGF may be beneficial in enhancing cholinergic neurochemical parameters, but the protective effects seem to be dependent on the continuous supply of NGF.

NGF rescues human B lymphocytes from anti-IgM induced apoptosis by activation of PKCzeta

Nerve growth factor (NGF) is a neurotrophic factor acting on both the peripheral and central nervous systems. In addition, it has been shown to modulate B lymphocyte function through receptors consisting of both p75 and TrkA proteins. The low-affinity NGFR, p75, shares structural homology with the B cell antigen, CD40, tumor necrosis factor (TNF) receptor and Fas antigen (APO-1), which play a role in cell apoptosis. We studied the effect of NGF on anti-IgM-induced apoptosis in human B lymphocytes and the role of protein kinase C (PKC) in this effect. Incubation of Ramos cells with anti-IgM (10 microg/ml) induced apoptosis which was observed after 6 h and reached plateau levels after 24 h. Addition of NGF to anti-IgM-treated cells rescued cells from apoptosis. The NGF effect was blocked by anti-NGF antibody and by K252a, a specific inhibitor for the tyrosine kinase activity of TrkA. NGF induced translocation of PKCdelta and PKCalpha from the cytosol to the plasma membrane and translocation of PKCzeta to the nucleus. To examine the role of PKC in the inhibitory effect of NGF on anti-IgM-induced apoptosis, we used inhibitors of PKCalpha and PKCdelta and found that these treatments did not alter the NGF effect. In contrast, treatment of the cells with oligonucleotide antisense directed against the 5' coding sequence of PKCzeta reduced the expression of PKCzeta in the cells and abolished the protective effect of NGF on anti-IgM-induced apoptosis. The translocation of PKCzeta and the protective effect of NGF were inhibited by the phosphatidylinositol 3 (PI3)-kinase inhibitors wortmannin and LY294002. The results of this study indicate that NGF is involved in B cell survival and that this effect is mediated by PI3-kinase-dependent activation of PKCzeta.

Interleukin-1 beta, but not IL-1 alpha, mediates nerve growth factor secretion from rat astrocytes via type I IL-1 receptor

In astrocytes, nerve growth factor (NGF) synthesis and secretion is stimulated by the cytokine interleukin-1 beta (IL-1 beta). In the present study, the role of IL-1 receptor binding sites in the regulation of NGF release was evaluated by determining the pharmacological properties of astroglially localized IL-1 receptors, and, by comparing the effects of both the agonists (IL-1 alpha and IL-1 beta) and the antagonist (IL-1ra)-members of the IL-1 family on NGF secretion from rat neonatal cortical astrocytes in primary culture. Using receptor-binding studies, binding of [(125)I] IL-1 beta to cultured astrocytes was saturable and of high affinity. Mean values for the K(D) and B(max) were calculated to be 60.7+/-7.4 pM and 2.5+/-0.1 fmol mg(-1) protein, respectively. The binding was rapid and readily reversible. IL-1 receptor agonists IL-1 alpha (K(i) of 341.1 pM) and IL-1 beta (K(i) 59.9 pM), as well as the antagonist IL-1ra (K(i) 257.6 pM), displaced specific [(125)I] IL-1 beta binding from cultured astrocytes in a monophasic manner. Anti-IL-1RI antibody completely blocked specific [(125)I] IL-1 beta binding while anti-IL-1RII antibody had no inhibitory effect. Exposure of cultured astrocytes to IL-1 alpha and IL-1 beta revealed the functional difference between the agonists in influencing NGF release. In contrast to IL-1 beta (10 U/ml), which caused a 3-fold increase in NGF secretion compared to control cells, IL-1 alpha by itself had no stimulatory action on NGF release. The simultaneous application of IL-1 alpha and IL-1 beta elicited no additive response. IL-1ra had no effect on basal NGF release but dose-dependently inhibited the stimulatory response induced by IL-1 beta. We concluded that IL-1 beta-induced NGF secretion from cultured rat cortical astrocytes is mediated by functional type I IL-1 receptors, whereas IL-1 alpha and IL-1ra, in spite of their affinity for IL-1RI, have no effect on NGF secretion from these cells. Type II IL-1R is not present on rat neonatal cortical astrocytes.

Maternal glucocorticoid hormone influences nerve growth factor expression in the developing rat brain

Rat pups nursed from birth by mothers with increased plasma corticosterone show long-lasting biochemical and behavioral modifications. Here we have investigated nerve growth factor (NGF) concentrations in the basal forebrain, prefrontal cortex and hippocampus of both male and female offspring at 11 days of age. Maternal hypercorticosteronemia was achieved by giving corticosterone-enriched water (200 microg/ml) from delivery. There was a significant increase of NGF in the basal forebrain of both sexes and no changes in the prefrontal cortex. In the hippocampus, an increase in NGF was found in males. These results indicate that a moderate increase of corticosterone in the lactating mother modulates NGF in the developing rat. We propose that these effects contribute directly to the long-lasting behavioral and biochemical modifications in pups nursed by hypercorticosteronemic mothers.

Under one roof: the Miami Project to Cure Paralysis model for spinal cord injury research

Concentrating a wide range of spinal cord injury (SCI) research laboratories in a single location to accelerate progress and draw attention to the promise of SCI research has made The Miami Project to Cure Paralysis one of the most publicly recognized and often controversial research groups in the neurosciences. A "Center of Excellence" at the University of Miami School of Medicine, the Miami Project also serves as a model for SCI research programs being developed nationally and internationally. Founded in 1985, the Miami Project set out on an unprecedented path-to develop a research center dedicated to improving treatments for SCI by bridging basic and clinical science. In doing so, neurosurgeon Barth Green, M.D., enlisted not only a multidisciplinary team of scientists but also a devoted following of financial donors and volunteer research subjects, and support from the University of Miami and Florida legislature. Highly visible spokespersons, including cofounder ex-Miami Dolphin Nick Buoniconti and his son Marc, brought the issue of SCI paralysis and the promise of research before the public, the media, and sports communities. As progress in the neurosciences has raced ahead, public attention to medical research, and SCI research in particular, has grown exponentially. This review will assess the Miami Project as a model for disease-based research that unites academic, philanthropic, and patient communities in a common cause.

Perinatal opioids reduce striatal nerve growth factor content in rat striatum

Both human and animal models indicate that perinatal methadone exposure produces a variety of short- and long-term neurobehavioral consequences, including disruption of normal development of striatal cholinergic neurons. Despite this, methadone maintenance is a standard method of managing pregnant heroin addicts, and the opioid receptor partial agonist buprenorphine is under evaluation for the same use. We now report that perinatal administration of either methadone or buprenorphine reduces the content of the neurotrophic factor nerve growth factor (NGF) in rat striatum, which may explain the behavioral deficits observed. Furthermore, although NGF content is reduced, there are no corresponding reductions in striatal NGF mRNA.

Data and hypotheses on the role of nerve growth factor and other neurotrophins in psychiatric disorders

Nerve growth factor (NGF) was discovered and characterized for its role on the growth, differentiation and maintenance of specific neurons of the peripheral nervous system. Subsequent studies revealed that NGF is synthesized and released within the central nervous system and exerts a trophic and functional role on basal forebrain cholinergic neurons; it is involved in a protective role following brain insults induced by an epileptic status, seizure, as well as surgical and chemical lesions.More recently our collaborative studies provided evidence that NGF is implicated in neurobehavioral response including cerebral alterations associated with psychiatric disorders. In this brief review, ongoing and emerging data are presented and discussed.

Nerve growth factor brain concentration and stress: changes depend on type of stressor and age

In the relationship between the hippocampus and the hypothalamo-pituitary-adrenocortical axis, trophic and tropic actions of nerve growth factor are involved in parallel with those on the cholinergic nuclei of the basal forebrain. Here, we report the changes produced by stress activation of the hypothalamo-pituitary-adrenocortical axis on hippocampal and basal forebrain nerve growth factor concentrations in 3-month-old male Wistar rats. The stressors used were: restraint; cold exposure; foot-shock; and rotatory platform. Restraint stress tended to reduce nerve growth factor in the hippocampus and reduced it significantly in the basal forebrain. Nerve growth factor levels in the hippocampus were not modified by cold exposure. However, a single unrepeated exposure significantly increased nerve growth factor in the basal forebrain. Both acute and chronic foot-shock reduced nerve growth factor in the hippocampus, leaving the levels in the basal forebrain unmodified. Acute but not chronic rotatory platform reduced nerve growth factor in the hippocampus, while showing a tendency, more pronounced after chronic application, toward an increase in the basal forebrain. Since with aging both activity of the hypothalamus-pituitary-adrenal axis and nerve growth factor trophic and tropic functions change, we studied the effect of restraint and cold stress in the 24-month-old male rat. The variations in nerve growth factor concentrations in the basal forebrain following stress activation are no longer present in the aged rat. The picture that emerges is indicative of a complex relationship between stress and nerve growth factor which is influenced by the kind of stressor and by age. Lack of uniformity in the effects produced by different stressors might reside in different qualitative and/or quantitative degree of involvement of neurotransmitters and/or neurohormones for each of them.

Studies in animal models and humans suggesting a role of nerve growth factor in schizophrenia-like disorders

Neurotrophic factors, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are known to play a crucial role in growth, differentiation and function in a variety of brain neurons during development and in adult life. We have recently shown that environmental changes, aggressive behavior and anxiety-like responses alter both circulating and brain basal NGF levels. In the present review, we present data obtained using animal models which suggest that neurotrophic factors, particularly NGF and BDNF, might be implicated in mechanism(s) leading to a condition associated with schizophrenic-like behaviors. The hypothesis that neurotrophins of the NGF family can be implicated in some maldevelopmental aspects of schizophrenia is supported by findings indicating that the constitutive levels of NGF and BDNF are affected in schizophrenic patients.

Effect of prenatal opioid exposure on cholinergic development

Opioid drugs such as methadone or buprenorphine are often used in the management of pregnant addicts. These drugs are generally thought of as nonteratogenic and preferable to repeated cycles of withdrawal in utero. However, evidence exists that perinatal exposure to these opioids delays and disrupts cholinergic development, particularly in the striatum. Acetylcholine (ACh) content and the expression of choline acetyltransferase protein and mRNA are reduced in the early postnatal period by prenatal opioid exposure in the rat. Although these indicators of the cholinergic phenotype return to normal levels over time, the activity of the cholinergic neurons remains disrupted, with a large increase in ACh turnover rate. The mechanism of these effects is unknown, but may involve changes in the expression of nerve growth factor, which is reduced by opioid exposure.

Brief exposure to neurotrophins produces a calcium-dependent increase in choline acetyltransferase activity in cultured rat septal neurons

We demonstrate that brief (30-min) exposure of cultured embryonic rat septal neurons to neurotrophins (NTs) increases choline acetyltransferase (ChAT) activity by 20-50% for all tested NTs (nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4, each at 100 ng/ml). The increase in ChAT activity was first detected 12 h after NT exposure, persisted at least 48 h, and was not mediated by increased neuronal survival or action-potential activity. Under some conditions, the response to brief NT exposure was as great as that produced by continuous exposure. NT stimulation of ChAT activity was inhibited by inhibitors of p75- and Trk kinase-mediated signaling, by removal of extracellular Ca2+ during the period of NT exposure, and by buffering intracellular Ca2+ with BAPTA. Application of nerve growth factor and brain-derived neurotrophic factor transiently increased [Ca2+] within a subpopulation of neurons. NT stimulation of ChAT activity was not affected significantly by cyclic AMP agonists or antagonists. These findings suggest that brief exposure to NTs can have a long-lasting effect on cholinergic transmission, and that this effect requires Ca2+, but not cyclic AMP.

Differential regulation of neurotrophin expression by mitogens and neurotransmitters in mouse lymphocytes

In this study, we examined the expression of neurotrophins in mouse lymphocytes and the regulation of their expression by mitogens and neurotransmitters. We found that mixed splenocytes as well as T and B lymphocytes expressed mRNA for all the neurotrophins examined. Differential regulation of the neurotrophins was obtained upon stimulation of the cells. Thus, LPS increased the expression of NGF, BDNF and NT-3 in splenocytes and B cells, whereas Con-A increased the mRNA of NT-3 and NT-4 in T cells and NGF expression in splenocytes. The neurotransmitter substance P and the beta-adrenergic agonist, isoproterenol induced an increase in the expression of NGF. Our results suggest an important role for the different neurotrophins in the function of the immune system and point to a bi-directional interaction between neurotrophins and neurotransmitters in this system.

NGF treatment potentiates c-fos expression in the rat nucleus basalis upon excitotoxic lesion with quisqualic acid

The induction of the c-fos gene in the rat brain by NGF was studied in a model of acute cholinergic hypofunction, i.e., the lesion of the nucleus basalis magnocellularis (NBM) with quisqualic acid. Choline acetyltransferase and Fos immunoreactivity (IR) in the NBM were analyzed at different times after the excitotoxic lesion. NGF treatment induced a potentiation of Fos expression 4 and 24 h after lesion. The possibility is discussed that c-fos induction is one of the early mechanisms of the neuroprotective action of NGF.

Model for aging in the basal forebrain cholinergic system

A key component of the cognitive deficits associated with aging is the loss of function of cholinergic neurons in the basal forebrain due to neuronal losses and decreased cholinergic function of spared neurons. A model to mimic one aspect of this phenomenon is to kill cholinergic neurons selectively in the basal forebrain via administration of the immunotoxin IgG-192-saporin. Here we discuss apoptotic regulators, such as nerve growth factor, in age-associated changes present in the cholinergic system and the role of the NF-kappaB signaling system in cellular commitment to apoptosis. We also examine the age-associated decline in intrinsic response mechanisms, which may account for the age-associated reduction in recovery from both acute and chronic insults to the central nervous system.

Enhanced visuospatial memory following intracerebroventricular administration of nerve growth factor

The present work assessed the effects of intracerebroventricular injections of rh recombined human nerve growth factor (rh NGF) (5 micrograms/2.5 microl) at postnatal days 12 and 13 upon the development of spatial learning capacities. The treated rats were trained at the age of 22 days to escape onto an invisible platform at a fixed position in space in a Morris navigation task. For half of the subjects, the training position was also cued, a procedure aimed at facilitating escape and at reducing attention to the distant spatial cues. Later, at the age of 6 months, all the rats were trained in a radial-arm maze task. Treatment effects were found in both immature and adult rats. The injection of NGF improved the performance in the Morris navigation task in both training conditions. There was a significant reduction in the escape latency and an increased bias toward the training platform quadrant during probe trials. The most consistent effect was the precocious development of an adult-like spatial memory. In the radial-arm maze, the NGF-treated rats made significantly fewer reentries than vehicle rats and this effect was particularly marked in the treated female rats. Taken together, these experiments reveal that the development and the maintenance of an accurate spatial representation are tightly related to the development of brain structures facilitated by the action of NGF. Moreover, these experiments demonstrate that an acute pharmacological treatment that leads to a transient modification in the choline acetyltransferase activity can induce a behavioral change long after the treatment.

Ciliary neurotrophic factor enhances the expression of NGF and p75 low-affinity NGF receptor in astrocytes

A functional interactions between ciliary neurotrophic factor (CNTF) and NGF has recently been demonstrated. We found that the exposure of rat cortical astrocytes to human recombinant CNTF for 3 h increased the level of mRNA for NGF as determined by reverse transcription-polymerase chain reaction (RT-PCR). The increase in NGF message was followed by corresponding increase in NGF protein secreted from the astrocytes into the culture medium as determined 6 h later. C-fos seemed to be involved in the mechanism of NGF induction since the expression of c-fos gene preceded NGF mRNA elevation. Furthermore, we found that in cultured astrocytes exogenous CNTF increased the level of mRNA coding for p75(NTR), the low affinity receptor for NGF and other neurotrophins. CNTF is highly expressed in the lesioned brain and CNTF-induced upregulation of NGF synthesis could be involved in the endogenous repair mechanisms.

Neuroprotection mediated via neurotrophic factors and induction of neurotrophic factors

Neurotrophins and other neurotrophic factors have been shown to support the survival and differentiation of many neuronal populations of the central and peripheral nervous system. Therefore, administering neurotrophic factors could represent an alternative strategy for the treatment of acute and chronic brain disorders. However, the delivery of neurotrophic factors to the brain is one of the largest obstacles in the development of effective therapy for neurodegenerative disorders, because these proteins are not able to cross the blood-brain barrier. The induction of growth factor synthesis in the brain tissue by systemically administered lipophilic drugs, such as beta-adrenoceptor agonists, shown to increase endogenous nerve growth factor (NGF) synthesis in the brain, would be an elegant way to overcome these problems of application. Stimulation of beta-adrenoceptors with clenbuterol led to increased NGF synthesis in cultured central nervous system (CNS) cells and rat brain tissue. Clenbuterol-induced NGF expression was reduced to the control levels by coadministration of beta-adrenoceptor antagonist propranolol. Furthermore, clenbuterol protected rat hippocampal neurons subjected to excitotoxic damage. The neuroprotective effect of clenbuterol in vitro depended on increased NGF synthesis, since the neuroprotection was abolished by NGF antisense oligonucleotide as well as by antibodies directed against NGF itself. In vivo, clenbuterol protected rat hippocampus in a model of transient forebrain ischemia and reduced the infarct volume in a rat model of permanent middle cerebral artery occlusion (MCAo). The neuroprotective effect of clenbuterol in vivo was accompanied by enhanced NGF synthesis in brain tissue. These findings support our hypothesis that orally active NGF inducers may have a potential as therapeutic agents for the treatment of neurodegenerative disorders and stroke.

Ciliary neurotrophic factor protects hippocampal neurons from excitotoxic damage

The loss of neurons is responsible for many acute neurological disorders as well as chronic neurodegenerative diseases. This cell loss might be prevented by a direct delivery of neurotrophic factors. Therefore, we investigated the capacity of ciliary neurotrophic factor (CNTF) and nerve growth factor (NGF) as well as the combination of both growth factors on the glutamate-induced excitotoxic damage in hippocampal cultures. The exposure of hippocampal neuronal/glial co-cultures to 0.5 mM L-glutamate for 1 h induced pronounced neurotoxicity evaluated 18 h later by trypan blue staining and morphological criteria. The damaged neurons showed both apoptotic and necrotic features. However, CNTF (1-1000 pg/ml) reduced neuronal degeneration when administered 6 and 24 h before induction of injury and remained in contact with the cells until evaluation of neuronal damage. Furthermore, NGF (1 ng/ml) also rescued the hippocampal neurons under the same experimental conditions and with a similar to CNTF potency. However, the co-administration of NGF and CNTF (but not either factor alone) restored the neuronal survival to control levels. Our results support the hypothesis that administering neurotrophic factors could represent an alternative strategy for the treatment of acute and chronic brain disorders.

Organization of the secretory machinery in the rodent brain: distribution of the t-SNAREs, SNAP-25 and SNAP-23

Vesicular transport events appear to be facilitated by the VAMP/synaptobrevin family of membrane proteins in the vesicle (v-SNAREs) and a heterodimeric complex of syntaxin and SNAP-23/25 family members in the target membrane (t-SNAREs). In this manuscript we examine the tissue distribution and composition of the heterodimeric t-SNARE complexes in adult rodent brain. Analysis of protein extracts from brain regions shows that SNAP-25, syntaxin 1, and 4 are broadly distributed, while SNAP-23, syntaxin 3, and 7 show distinct patterns of expression. Further immunohistochemistry and fractionation studies show that while SNAP-25 is enriched in axons and nerve terminals, SNAP-23 is concentrated in cell bodies. Both SNAP-23 and SNAP-25 associate with the plasma membrane and can be metabolically labeled with [(3)H] palmitate in AtT-20 cells. Anti-SNAP-25 antibodies co-immunoprecipitate t-SNARE heterodimers from brain extracts that predominantly contain syntaxin 1 and 2. Contrary to results from in vitro binding assays, SNAP-23 was found predominantly associated with syntaxin 3. These observations suggest that t-SNARE, heterodimer composition is governed more by SNARE expression and localization than by simple protein-protein affinity.

TrkA expression in mouse olfactory tract following axotomy of olfactory nerves

The olfactory bulb is one of the brain regions that synthesizes the nerve growth factor (NGF). Functional roles of the bulbar NGF remain to be determined. The aim of the present study was, using an antibody specific to the high-affinity NGF receptor (trkA), to examine immunohistochemically the distribution of the NGF receptor in the mouse olfactory tract, under normal conditions and during regenerative processes. In normal mouse olfactory epithelia, trkA immunoreactive cell bodies were only seen in basal cells. Cell bodies of olfactory receptor cells did not express trkA immunoreactivity, but their neuronal processes (olfactory nerve fibres and bundles in the olfactory mucosa and the olfactory bulb) displayed trkA immunoreactivity. After axotomy of olfactory nerves, regenerating olfactory cells (basal cells and olfactory receptor cells) expressed trkA immunoreactivity in intramucosal and intrabulbar neuronal processes of olfactory receptor cells. These results suggest involvement of the bulbar NGF in the process of synaptogenesis and/or regeneration of the olfactory nervous system.

Effects of NGF, b-FGF, and cerebrolysin on water maze performance and on motor activity of rats: short- and long-term study

The effects of 14-day treatments with nerve growth factor (NGF), basic fibroblast growth factor (b-FGF), or the peptidergic drug Cerebrolysin on postlesion acquisition of a water maze task and on motor activity were evaluated. Rats were tested in the Morris water maze 14 days (early test) and 7 to 8 months (delayed test) after a bilateral lesion of the frontoparietal (sensorimotor) cortex. Only the rats treated with Cerebrolysin performed the water maze task at the level of the nonlesioned controls in the early test. No short-term effect of NGF (6.5 ng/14 days; 38 ng/ml) or b-FGF (17 ng/14 days; 100 ng/ml) treatment was found. The delayed test revealed that water maze performance was restored in rats treated with b-FGF in comparison with intact controls. The data showed that b-FGF can support or initiate processes in the CNS that lead to a delayed functional amelioration and/or compensation for a water maze performance deficit. NGF did not influence the acquisition impairment caused by a sensorimotor cortical lesion. Two-week administration of Cerebrolysin had a time-dependent influence: it attenuated the acquisition deficit and increased the motor activity of rats, both effects declined to the level of lesioned controls within 8 months.

Distribution and retrograde transport of trophic factors in the central nervous system: functional implications for the treatment of neurodegenerative diseases

Neurotrophins play a crucial role in the maintenance, survival and selective vulnerability of various neuronal populations within the normal and diseased brain. Several families of growth promoting substances have been identified within the central nervous system (CNS) including the superfamily of nerve growth factor related neurotrophin factors, glial derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF). In addition, other non-neuronal growth factors such as fibroblast growth factor (FGF) have also been identified. This article reviews the trophic anatomy of these factors within the CNS. Intraventricular and intraparenchymal injections of exogenous nerve growth factor result in retrograde labeling mainly within the cholinergic basal forebrain. Distribution of brain derived neurotrophic factor (BDNF) following intraventricular injection is minimal due to the binding to the trkB receptor along the ventricular wall. In contrast, intraparenchymal injections of BDNF results in widespread retrograde transport throughout the CNS. BDNF has also been shown to be transported anterogradely within the CNS. Infusion of GDNF into the CNS results in retrograde transport limited to the nigrostriatal pathway. Hippocampal injections of NT-3 retrogradely label mainly basal forebrain neurons. Retrograde transport of radiolabeled CNTF has only been observed in sensory neurons of the sciatic nerve. Following intraventricular and intraparenchymal infusion of radiolabeled bFGF, retrograde neuronal labeling was found in the telecephalon, diencephalon, mesencephalon and pons. In contrast retrograde labeling for aFGF was found only in the hypothalamus and midbrain. Since select neurotrophins traffic anterogradely and retrogradely within the nervous system, these proteins could be used to treat neurological diseases such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.