Selective antibody-induced cholinergic cell and synapse loss produce sustained hippocampal and cortical hypometabolism with correlated cognitive deficits

The physiological interrelationships between cognitive impairments, neurotransmitter loss, amyloid processing and energy metabolism changes in AD, cholinergic dementia and Down's syndrome are largely unknown to date. This report contains novel studies into the association between cognitive function and cerebral metabolism after long-term selective CNS cholinergic neuronal and synaptic loss in a rodent model. We measured local cerebral rates of glucose utilization ((14)C-2-deoxyglucose) throughout the brains of awake rats 4.5 months after bilateral intraventricular injections of a cholinotoxic antibody directed against the low-affinity NGF receptor (p75 NGF) associated with cholinergic neurons (192 IgG-saporin). Permanent cholinergic synapse loss was demonstrated by [(3)H]-vesamicol in vitro autoradiography defining presynaptic vesicular acetylcholine (ACh) transport sites. While other metabolic studies have defined acute and transient glucose use changes after relatively nonspecific lesions of anatomical regions containing cholinergic neurons, our results show sustained reductions in glucose utilization in brain regions impacted by cholinergic synapse loss, including frontal cortical and hippocampal regions, relative to glucose use levels in control rats. In the same animals, impaired cognitive spatial performance in a Morris water maze was correlated with reduced glucose use rates in the cortex and hippocampus at this time point, which is consistent with increased postmortem cortical and hippocampal amyloid precursor protein (APP) levels (45, 46). These results are consistent with the view of cholinergic influence over metabolism, APP processing, and cognition in the cortex and hippocampus.

Immunophilin ligands can prevent progressive dopaminergic degeneration in animal models of Parkinson's disease

Slowing or halting the progressive dopaminergic (DA) degeneration in Parkinson's disease (PD) would delay the onset and development of motor symptoms, prolong the efficacy of pharmacotherapies and decrease drug-induced side-effects. We tested the potential of two orally administered novel immunophilin ligands to protect against DA degeneration in two animal models of PD. First, in an MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model, we compared an immunophilin ligand (V-10,367) documented to bind the immunophilin FKBP12 with V-13,661, which does not bind FKBP12. Both molecules could prevent the loss of striatal DA innervation in a dose-dependent fashion during 10 days of oral administration. Second, to determine whether an immunophilin ligand can protect against progressive and slow DA degeneration typical of PD, an intrastriatal 6-hydroxydopamine-infusion rat model was utilized. Oral treatment with the FKBP12-binding immunophilin ligand began on the day of lesion and continued for 21 days. At this time point, post mortem analyses revealed that the treatment had prevented the progressive loss of DA innervation within the striatum and loss of DA neurons within the substantia nigra, related to functional outcome as measured by rotational behaviour. Notably, DA fibres extending into the area of striatal DA denervation were observed only in rats treated with the immunophilin ligand, indicating neuroprotection or sprouting of spared DA fibres. This is the first demonstration that immunophilin ligands can prevent a slow and progressive DA axonal degeneration and neuronal death in vivo. The effects of orally administered structurally related immunophilin ligands in acute and progressive models of DA degeneration are consistent with the idea that these compounds may have therapeutic value in PD.

Neuroimmunophilin ligand enhances neurite outgrowth and effect of fetal dopamine transplants

Neuroimmunophilin ligands have been shown to enhance neurite outgrowth in several neuronal systems in culture, including primary dopaminergic neurons from fetal ventral mesencephalon. We investigated the ability of neuroimmunophilin ligands to enhance outgrowth of transplanted fetal dopamine neurons in vivo. Rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal dopamine system were transplanted with rat embryonic day 14 ventral mesencephalon into the striatum, then treated orally with a neuroimmunophilin ligand (15mg/kg) or vehicle once per day for 14 days. All transplanted animals regained dopamine function over a 10 week behavioral test period, as indicated by decrease and reversal of amphetamine-induced rotation. In addition, neuroimmunophilin ligand-treated animals showed a more pronounced motor response during the first 10min after amphetamine injection, possibly reflecting increased striatal reinnervation or increased functional capacity. At post-mortem analyses, neuroimmunophilin ligand-treated rats showed a significantly higher density of tyrosine hydroxylase-positive fibers reinnervating the lesioned striatum, both immediately surrounding the transplant (92% of unlesioned density in neuroimmunophilin-treated rats vs 67% of unlesioned levels in vehicle-treated rats) and at some distance from the transplant/host interface. The number of tyrosine hydroxylase-positive cells within the transplants was not different between groups. This study demonstrates that short-term oral administration of a neuroimmunophilin ligand can enhance neurite outgrowth from fetal dopamine neuronal transplants.

Transplanted fetal striatum in Huntington's disease: phenotypic development and lack of pathology

Neural and stem cell transplantation is emerging as a potential treatment for neurodegenerative diseases. Transplantation of specific committed neuroblasts (fetal neurons) to the adult brain provides such scientific exploration of these new potential therapies. Huntington's disease (HD) is a fatal, incurable autosomal dominant (CAG repeat expansion of huntingtin protein) neurodegenerative disorder with primary neuronal pathology within the caudate-putamen (striatum). In a clinical trial of human fetal striatal tissue transplantation, one patient died 18 months after transplantation from cardiovascular disease, and postmortem histological analysis demonstrated surviving transplanted cells with typical morphology of the developing striatum. Selective markers of both striatal projection and interneurons such as dopamine and c-AMP-related phosphoprotein, calretinin, acetylcholinesterase, choline acetyltransferase, tyrosine hydroxylase, calbindin, enkephalin, and substance P showed positive transplant regions clearly innervated by host tyrosine hydroxylase fibers. There was no histological evidence of immune rejection including microglia and macrophages. Notably, neuronal protein aggregates of mutated huntingtin, which is typical HD neuropathology, were not found within the transplanted fetal tissue. Thus, although there is a genetically predetermined process causing neuronal death within the HD striatum, implanted fetal neural cells lacking the mutant HD gene may be able to replace damaged host neurons and reconstitute damaged neuronal connections. This study demonstrates that grafts derived from human fetal striatal tissue can survive, develop, and are unaffected by the disease process, at least for 18 months, after transplantation into a patient with HD.

Neurotrophic factors NGF and FGF-2 alter levels of huntingtin (IT15) in striatal neuronal cell cultures

A mutation of the human IT15 gene is responsible for Huntington's disease (HD) and the causative factor in the major neuronal loss observed in the striatum. The growth factors basic fibroblast growth factor (FGF-2), nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF) improve survival and promote differentiation of striatal neurons, as well as exert a neuroprotective effect when such neurons are challenged with metabolic toxins or excitatory amino acids. Using Western blotting and striatal cell cultures, we found that FGF-2 increased the level of huntingtin in a dose-dependent fashion, whereas NGF decreased huntingtin expression. The neurotrophic factor-specific, dose-dependent effect on striatal levels of huntingtin may be relevant to understanding the normal role of IT15 and developing new therapies against the disease provoking mutated IT15.

Immunophilin ligands and GDNF enhance neurite branching or elongation from developing dopamine neurons in culture

Neurotrophic effects of immunophilin ligands have been shown in animal models of peripheral and central nervous system insult. To investigate the specific growth-promoting effects of these compounds, we examined the effects of various immunophilin ligands on primary dopamine (DA) neurons in culture and compared these with a well-known DA trophic factor, glial cell line-derived neurotrophic factor (GDNF). In neuronal cultures from Embryonic Day 14 ventral mesencephalon, enhanced elongation of DA neurites was observed with immunophilin ligands, which inhibited the phosphatase activity of calcineurin (FK506 and cyclosporin A) when compared to vehicle-treated cultures. This elongation was also observed with GDNF, known to exert its trophic effects through phosphorylation-dependent pathways. In contrast, immunophilin ligands that do not inhibit calcineurin (rapamycin and V-10,367) increased branching of DA neurites, suggesting that elongation is dependent upon maintained phosphorylation while branching is not. In addition, both V-10,367 and rapamycin antagonized the elongation effects of FK506 and induced branching. The antagonism of elongation (and reappearance of branching) illustrates the intrinsic abilities of developing DA neurons to either elongate or branch, but not both. We show that the immunophilin FKBP12 (12-kDa FK506-binding protein) is expressed in ventral mesencephalic neuronal cultures and colocalizes with DA neurons. This work elucidates the specific growth-promoting effects by which GDNF and immunophilin ligands modify developmental growth processes of DA neurons, via their interactions with intracellular targets.

Impact of genomics on drug discovery and clinical medicine

Genomics, particularly high-throughput sequencing and characterization of expressed human genes, has created new opportunities for drug discovery. Knowledge of all the human genes and their functions may allow effective preventive measures, and change drug research strategy and drug discovery development processes. Pharmacogenomics is the application of genomic technologies such as gene sequencing, statistical genetics, and gene expression analysis to drugs in clinical development and on the market. It applies the large-scale systematic approaches of genomics to speed the discovery of drug response markers, whether they act at the level of the drug target, drug metabolism, or disease pathways. The potential implication of genomics and pharmacogenomics in clinical research and clinical medicine is that disease could be treated according to genetic and specific individual markers, selecting medications and dosages that are optimized for individual patients. The possibility of defining patient populations genetically may improve outcomes by predicting individual responses to drugs, and could improve safety and efficacy in therapeutic areas such as neuropsychiatry, cardiovascular medicine, endocrinology (diabetes and obesity) and oncology. Ethical questions need to be addressed and guidelines established for the use of genomics in clinical research and clinical medicine. Significant achievements are possible with an interdisciplinary approach that includes genetic, technological and therapeutic measures.

Transplantation of embryonic porcine mesencephalic tissue in patients with PD

OBJECTIVE

To assess the safety and the effect on standardized clinical rating measures of transplanted embryonic porcine ventral mesencephalic (VM) tissue in advanced PD.

METHODS

Twelve patients with idiopathic PD underwent unilateral implantation of embryonic porcine VM tissue; six received cyclosporine immunosuppression and six received tissue treated with a monoclonal antibody directed against major histocompatibility complex class I. Patients were followed for 12 months and assessed by clinical examination, MRI, and 18F-levodopa PET. Porcine endogenous retrovirus testing was conducted by PCR-based method on peripheral blood mononuclear cells.

RESULTS

Cell implantation occurred without serious adverse events in all patients. Cultures were negative for bacterial and unknown viral contamination. No porcine endogenous retrovirus DNA sequences were found. MRI demonstrated cannula tracts within the putamen and caudate, with minimal or no edema and no mass effect at the transplant sites. In the medication-off state, total Unified Parkinson's Disease Rating Scale scores improved 19% (p = 0.01). Three patients improved over 30%. There were two patients with improved gait. 18F-levodopa PET failed to show changes on the transplanted side.

CONCLUSIONS

Unilateral transplantation of porcine embryonic VM cells into PD patients was well tolerated with no evidence of transmission of porcine endogenous retrovirus. Changes in standardized clinical PD rating measures were variable, similar to the results of the first trials of unilateral human embryonic allografts that transplanted small amounts of tissue.

Porcine xenografts in Parkinson's disease and Huntington's disease patients: preliminary results

The observation that fetal neurons are able to survive and function when transplanted into the adult brain fostered the development of cellular therapy as a promising approach to achieve neuronal replacement for treatment of diseases of the adult central nervous system. This approach has been demonstrated to be efficacious in patients with Parkinson's disease after transplantation of human fetal neurons. The use of human fetal tissue is limited by ethical, infectious, regulatory, and practical concerns. Other mammalian fetal neural tissue could serve as an alternative cell source. Pigs are a reasonable source of fetal neuronal tissue because of their brain size, large litters, and the extensive experience in rearing them in captivity under controlled conditions. In Phase I studies porcine fetal neural cells grafted unilaterally into Parkinson's disease (PD) and Huntington's disease (HD) patients are being evaluated for safety and efficacy. Clinical improvement of 19% has been observed in the Unified Parkinson's Disease Rating Scale "off" state scores in 10 PD patients assessed 12 months after unilateral striatal transplantation of 12 million fetal porcine ventral mesencephalic (VM) cells. Several patients have improved more than 30%. In a single autopsied PD patient some porcine fetal VM cells were observed to survive 7 months after transplantation. Twelve HD patients have shown a favorable safety profile and no change in total functional capacity score 1 year after unilateral striatal placement of up to 24 million fetal porcine striatal cells. Xenotransplantation of fetal porcine neurons is a promising approach to delivery of healthy neurons to the CNS. The major challenges to the successful use of xenogeneic fetal neuronal cells in neurodegenerative diseases appear to be minimizing immune-mediated rejection, management of the risk of xenotic (cross-species) infections, and the accurate assessment of clinical outcome of diseases that are slowly progressive.

Gene therapy in the CNS

Gene therapy for neurological disorder is currently an experimental concept. The goals for clinical utilization are the relief of symptoms, slowing of disease progression, and correction of genetic abnormalities. Experimental studies are realizing these goals in the development of gene therapies in animal models. Discoveries of the molecular basis of neurological disease and advances in gene transfer systems have allowed focal and global delivery of therapeutic genes for a wide variety of CNS disorders. Limitations are still apparent, such as stability and regulation of transgene expression, and safety of both vector and expressed transgene. In addition, the brain adds several challenges not seen in peripheral gene therapy paradigms, such as post-mitotic cells, heterogeneity of cell types and circuits, and limited access. Moreover, it is likely that several modes of gene delivery will be necessary for successful gene therapies of the CNS. Collaborative efforts between clinicians and basic researchers will likely yield effective gene therapy in the CNS.

Cognitive changes and modified processing of amyloid precursor protein in the cortical and hippocampal system after cholinergic synapse loss and muscarinic receptor activation

A number of in vitro studies have shown that activation of muscarinic receptors by cholinergic agonists stimulates the nonamyloidogenic, alpha-secretase-processing pathway of amyloid precursor protein (APP). To determine whether increased cholinergic neurotransmission can modify the APP processing in vivo, we administered a muscarinic receptor agonist (RS86) to normal or aged rats and rats with severe basal forebrain cholinergic deficits (induced by 192 IgG-saporin). The levels of the cell-associated APP in neocortex, hippocampus, and striatum, as well as the secreted form of APP (APPs) in cerebrospinal fluid, were examined by Western blots. Additionally, we investigated the association between the altered APP levels and behavioral deficits caused by cholinergic lesions. We found that treatment with muscarinic receptor agonist resulted in decreased APP levels in neocortex and hippocampus and increased levels of APPs in cerebrospinal fluid. Regulation of APP processing by the muscarinic agonist treatment occurred not only in normal rats, but also in aged and cholinergic denervated rats that model this aspect of Alzheimer's disease. Interestingly, we found that elevation of APP in neocortex correlated with the cognitive deficits in water-maze testing of rats with cholinergic dysfunction. These data indicate that increased cholinergic neurotransmission can enhance nonamyloidogenic APP processing in intact and lesioned rats and that APP may be involved in cognitive performance.

Gene transfer to the nigrostriatal system by hybrid herpes simplex virus/adeno-associated virus amplicon vectors

To improve gene transfer to CNS neurons, critical elements of herpes simplex virus 1 (HSV-1) amplicons and recombinant adeno-associated virus (AAV) vectors were combined to construct a hybrid amplicon vector, and then packaged via a helper virus-free system. We tested the HSV/AAV hybrid amplicon vectors for transduction efficiency and stability of transgene expression (green fluorescent protein) in primary neuronal cultures from rat fetal ventral mesencephalon, in comparison with traditional HSV amplicon, AAV, or adenovirus (Ad) vectors at the same multiplicity of infection. The HSA/AAV hybrid vectors transduced the highest number of primary neurons in culture 2 days after infection. As compared with all other vectors tested, only hybrid vectors containing the AAV rep gene maintained the 2-day level of transgene expression over 12 days in culture. This rep-containing hybrid vector was then tested for efficiency and safety in the brain. One month after injection into adult rat striatum (1 x 10(6) transducing units injected), transgene expression was observed within the striatum (ranging from 564 to 8610 cells) and the substantia nigra (via retrograde transport, ranging from 130 to 809 neurons). The HSV/AAV hybrid amplicon vectors transduced predominantly neurons within the striatum, and showed transduction efficacy similar to and in many cases higher than that of HSV amplicon vectors. No immune response was observed in the HSA/AAV hybrid vector-injected brains, as determined by immune markers specific for helper T lymphocytes, cytotoxic T lymphocytes, and microglia. This HSV/AAV hybrid system shows high transduction efficiency and stability in culture. The effective and safe transgene delivery into the nigrostriatal system illustrates its potential for therapeutic application for neurologic disorders, such as Parkinson and Huntington disease.

Detection of dopaminergic cell loss and neural transplantation using pharmacological MRI, PET and behavioral assessment

We demonstrate the use of magnetic resonance imaging (MRI) for detection of neurotransmitter stimulation using the dopamine transporter ligands amphetamine and CFT (2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane) as pharmacological challenges. We demonstrate that the unilateral loss of a hemodynamic response to either amphetamine or CFT challenge by unilateral 6-hydroxydopamine lesioning is restored by transplantation of fetal dopamine neurons in the striatum. The time course for the hemodynamic changes parallels the time courses for dopamine release, measured by prior microdialysis studies, and also for the rotational behavior in the unilaterally lesioned animals. Transplantation of the fetal cells results in hemodynamic time courses after CFT or amphetamine challenges at the graft site that are identical to those induced both before transplantation and on the intact contralateral side. The transplantation also results in complete behavioral recovery. The spatial extent of the dopaminergic recovery in the lesioned striatum is the same when measured using either PET of tracer levels of [11C]CFT binding or MRI. These results show great promise for the application of pharmacological MRI for application to studies of dopamine cell loss and potential recovery in Parkinson's disease.

Cellular delivery of trophic factors for the treatment of Huntington's disease: is neuroprotection possible?

The elucidation of the genetic defect in patients with Huntington's disease (HD) has allowed for the detection of individuals at risk for HD prior to the onset of symptoms. Thus "neuroprotection strategies" aimed at preventing the neuropathological and behavioral sequelae of this disease might be powerful therapeutically since they could be introduced to healthy patients before the initiation of a massive degenerative cascade principally localized to the striatum. A variety of trophic factors potently protect vulnerable striatal neurons in animal models of HD. A number of experimental variables are critical in determining the success of trophic factors in animal models. In this regard, the method of trophic factor delivery may be crucial, as delivery via genetically modified cells often produces greater and more widespread effects on striatal neurons than infusions of that same factor. The mechanisms by which cellularly delivered trophic factors forestall degeneration and prevent behavioral deficits are complex and often appear to be unrelated to the trophic factor binding to its cognate receptor. In this regard, cells genetically modified to secrete nerve growth factor (NGF) or ciliary neurotrophic factor (CNTF) protect degenerating striatal neurons which do not express either NGF or CNTF receptors. This review will discuss some of the non-receptor-based events that might underlie these effects and present the hypothesis that cellular delivery of certain trophic factors using genetically modified cells may be ready for clinical testing in HD patients.

Factors intrinsic to the neuron can induce and maintain its ability to promote axonal outgrowth: a role for BCL2?

The adult CNS provides a poor environment for axonal growth and regeneration. The question of to what extent the loss of axonal growth occurring as the brain matures is dependent on factors intrinsic or extrinsic to the growing neuron is still unanswered. Examination of axonal growth from neural transplants provides insight into the roles of growth factors, inhibitory molecules, growth-promoting substrates and the differences between CNS and PNS environments in the regulation of neurite extension. The data that imply a role for BCL2 and related molecules in such processes are reviewed in this article, which analyzes the factors intrinsic to the neuron that control its capacity for axonal growth.

Dopamine imaging markers and predictive mathematical models for progressive degeneration in Parkinson's disease

We conducted PET imaging studies of modulation of dopamine transporter function and MRS studies of neurochemicals in idiopathic primate Parkinson's disease (PD) model induced by long-term, low-dose administration of MPTP. MR spectra showed striking similarities of the control spectrum of the primate and human striatum as well as MPTP-treated primate (six months after cessation of MPTP), and Parkinson's disease patient striatum (68 year old male; Hoehn-Yahr scale II; 510 mg/d L-DOPA). The choline/creatine ratio was similar in the MPTP model and human parkinsonism, suggesting a possible glial abnormality. The progressive degeneration of dopamine re-uptake sites observed in our PD model can be expressed by a time dependent exponential equation N(t) = N0 exp (-(0.072 +/- 0.016) t), where N0 represents intact entities (dopamine re-uptake sites before MPTP) and 0.072 per month is the rate of degeneration. When the signs of PD appear, N(t) is about 0.3-0.4 times N0. Interestingly, this biological degenerative phenomena has similar progression to that observed in cell survival theory. According to this theory and calculated degeneration rate, predictive models can be produced for regeneration and protective treatments.

Apoptosis in neuronal development and transplantation: role of caspases and trophic factors

Fetal ventral mesencephalic (VM) transplants have been studied in the context of dopaminergic (DA) replacement therapy for Parkinson's disease (PD). DA neurons from VM transplants will grow axons and form functional synapses in the adult host central nervous system (CNS). Recently, studies have demonstrated that most of the transplanted DA neurons die in grafts within the first week after implantation. An important feature of neural development, also in transplanted developing fetal neural tissue, is cell death. However, while about 50% of cells born in the CNS will die naturally, up to 99% of fetal cells die after neural transplantation. It has been shown that VM grafts contain many apoptotic cells even at 14 days after transplantation. The interleukin-1beta converting enzyme (ICE) cysteine protease and 11 other ICE-like-related proteases have been identified, now named caspases. Activation of caspases is one of the final steps before a neuron is committed to die by apoptosis. Here we review this cell death process in detail: Since the growth of fetal neural grafts placed in the adult brain in many ways mimics normal development, it is likely that the caspases also play a functional role in transplants. Pharmacological inhibitors of caspases and genetically modified mice are now available for the study of neuronal death in fetal neuronal transplants. Understanding cell death mechanisms involved in acute cellular injury, necrosis, and programmed cell death (PCD) is useful in improving future neuronal transplantation methodology, as well as in neuroprotection, for patients with neurodegenerative diseases.

Pig fetal septal neurons implanted into the hippocampus of aged or cholinergic deafferented rats grow axons and form cross-species synapses in appropriate target regions

The anatomical specificity of axon growth from fetal pig septal xenografts was studied by transplanting septal cells from E30-35 pig fetuses into cholinergic deafferented (192-IgG-saporin-infused) rats or into aged rats (> 18 months). Cell suspensions (100,000 cells/microl) were injected bilaterally into the dorsal and ventral hippocampus of immunosuppressed rats (10 mg/kg/day cyclosporine A). To assess axonal growth and synapse formation, acetylcholinesterase histochemistry, an antibody to choline acetyltransferase (ChAT), and three pig-positive/rat-negative antibodies: bovine 70kD neurofilament (NF70), human low-affinity NGF receptor (hNGFr), and human synaptobrevin (hSB) were used. In rats with surviving grafts at 6 months, NF70 axonal labeling was more extensive than either ChAT or hNGFr labeling. All three markers demonstrated graft axons extending selectively through the hippocampal CA fields and the molecular layer of the dentate gyrus. Graft axons did not extend into adjacent entorhinal cortex or neocortex. The distribution of pig hSB-positive synapses correlated with AChE-positive fiber outgrowth in to the host. Electron microscopic analysis of hSB-immunostained hippocampal sections revealed pig presynaptic terminals in contact with normal rat postsynaptic structures in the CA fields and the dentate gyrus. These data demonstrate target-appropriate growth of pig cholinergic axons and the formation of cross-species synapses in the deafferented or aged rat hippocampus.

Morris water maze analysis of 192-IgG-saporin-lesioned rats and porcine cholinergic transplants to the hippocampus

Adults rats were lesioned with 192-IgG-saporin, an immunotoxin that targets cholinergic neurons in the basal forebrain expressing the low-affinity nerve growth factor receptor (p75). One month later, rats received E30-35 porcine cholinergic neurons bilaterally into the hippocampus, and were tested in the Morris water maze and the passive avoidance task 4.5-6 months after transplantation (in two experiments, rats were retested in the water maze) followed by histological and cellular analyses. The 192-IgG-saporin-lesioned animals displayed clear cognitive deficits in the Morris water maze. In all experiments the lesioned animals had spatial probe deficits on day 5 testing. A large variance was found among the transplanted animals, with individual animals exhibiting improved performance, but little overall improvement when compared to lesion-alone animals as a group. The relationships between behavioral performance and graft cholinergic factors were established by histological analyses. Grafted animals exhibited an increase in cholinergic innervation of the dentate gyrus (DG) region of the dorsal hippocampus when compared to lesion-alone animals. There was a significant correlation between the level of cholinergic innervation in the dentate gyrus and spatial navigation performance (latency and spatial probe) in the Morris water maze task. These data provide evidence of memory and spatial deficits following cholinergic denervation, and of target-specific growth of xenogeneic cholinergic neurons into the hippocampus. The lack of a clear treatment (transplant) effect in the behavioral measures leads us to believe that functional restoration of cognitive function would require cholinergic reinnervation of both the hippocampus and the neocortex in this 192-IgG-saporin animal model.

Combined PET/MRS brain studies show dynamic and long-term physiological changes in a primate model of Parkinson disease

We used brain imaging to study long-term neurodegenerative and bioadaptive neurochemical changes in a primate model of Parkinson disease. We gradually induced a selective loss of nigrostriatal dopamine neurons, similar to that of Parkinson disease, by creating oxidative stress through infusion of the mitochondrial complex 1 inhibitor MPTP for 14+/-5 months. Repeated evaluations over 3 years by positron emission tomography (PET) demonstrated progressive and persistent loss of neuronal dopamine pre-synaptic re-uptake sites; repeated magnetic resonance spectroscopy (MRS) studies indicated a 23-fold increase in lactate and macromolecules in the striatum region of the brain for up to 10 months after the last administration of MPTP. By 2 years after the MPTP infusions, these MRS striatal lactate and macromolecule values had returned to normal levels. In contrast, there were persistent increases in striatal choline and decreases in N-acetylaspartate. Thus, these combined PET/MRS studies demonstrate patterns of neurochemical changes that are both dynamic and persistent long after selective dopaminergic degeneration.

A novel immunophilin ligand: distinct branching effects on dopaminergic neurons in culture and neurotrophic actions after oral administration in an animal model of Parkinson's disease

Protection or regeneration of the dopaminergic (DA) system would be of significant therapeutic value for Parkinson's disease. Immunophilin ligands, such as FK506, can produce neurotrophic effects in vitro and in vivo, but their immunosuppressive effects make them unsuitable for neurological application. This study demonstrates that a novel, nonimmunosuppressive immunophilin ligand (V-10,367) increased the number of neurites extended by tyrosine hydroxylase positive (TH+) DA neurons in embryonic day 14 primary DA neuronal cultures. In contrast, the immunosuppressive immunophilin ligand FK506 increased the length of TH+ neurites. After oral administration in MPTP-treated mice, V-10,367 completely protected against MPTP-induced loss of striatal TH+ axonal density, while FK506 did not. These experiments demonstrate that nonimmunosuppressive immunophilin ligands specifically increase neurite branching in primary DA neuronal culture and possess neurotrophic actions in vivo with potential application to neurodegenerative disease.